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X11VNC(1)			 User Commands			     X11VNC(1)

       x11vnc -	allow VNC connections to real X11 displays
		version: 0.9.16, lastmod: 2019-01-05

       x11vnc [OPTION]...

       Typical usage is:

	      Run  this	 command  in  a	shell on the remote machine "far-host"
	      with X session you wish to view:

	      x11vnc -display :0

	      Then run this in another window on the machine you  are  sitting

	      vncviewer	far-host:0

       Once x11vnc establishes connections with	the X11	server and starts lis-
       tening as a VNC server it will print out	a string: PORT=XXXX where XXXX
       is  typically  5900  (the default VNC server port).  One	would next run
       something like this on the local	machine: "vncviewer hostname:N"	 where
       "hostname"  is  the  name of the	machine	running	x11vnc and N is	XXXX -
       5900, i.e. usually "vncviewer hostname:0".

       By default x11vnc will not allow	the screen to be shared	 and  it  will
       exit as soon as the client disconnects.	See -shared and	-forever below
       to override these protections.  See the FAQ for details how  to	tunnel
       the  VNC	 connection  through  an encrypted channel such	as ssh(1).  In

	      ssh -t -L	5900:localhost:5900 far-host 'x11vnc -localhost	 -dis-
	      play :0'

       % vncviewer -encodings 'copyrect	tight zrle hextile' localhost:0

       Also,  use of a VNC password (-rfbauth or -passwdfile) is strongly rec-

       For   additional	  info	 see:   and

       Config  file support: if	the file $HOME/.x11vncrc exists	then each line
       in it is	treated	as a single command line option.  Disable with	-norc.
       For  each option	name, the leading character "-"	is not required.  E.g.
       a line that is either "forever" or  "-forever"  may  be	used  and  are
       equivalent.   Likewise  "wait  100"  or	"-wait 100" are	acceptable and
       equivalent lines.  The "#" character comments out to  the  end  of  the
       line in the usual way (backslash	it for a literal).  Leading and	trail-
       ing whitespace is trimmed off.  Lines may be continued with  a  "\"  as
       the last	character of a line (it	becomes	a space	character).

       -display	disp

	      X11  server  display  to	connect	 to, usually :0.  The X	server
	      process must be running on same  machine	and  support  MIT-SHM.
	      Equivalent to setting the	DISPLAY	environment variable to	disp.

	      See  the	description  below  of the "-display WAIT:..."	exten-
	      sions, where alias "-find" will find the user's display automat-
	      ically,  and  "-create" will create a Xvfb session if no session
	      is found.

       -auth file

	      Set the X	authority file to be file, equivalent to  setting  the
	      XAUTHORITY environment variable to file before startup.  Same as
	      -xauth file.  See	Xsecurity(7) , xauth(1)	 man  pages  for  more

	      Use  '-auth  guess'  to  have x11vnc use its -findauth mechanism
	      (described below)	to try to guess	the  XAUTHORITY	 filename  and
	      use it.

	      XDM/GDM/KDM:  if you are running x11vnc as root and want to find
	      the XAUTHORITY before anyone has logged into an X	 session  yet,
	      use:  x11vnc -env	FD_XDM=1 -auth guess ...  (This	will also find
	      the XAUTHORITY if	a user is already logged into the X  session.)
	      When  running  as	 root,	FD_XDM=1  will be tried	if the initial
	      -auth guess fails.


	      If the X display is :N, try to set the VNC display to also be :N
	      This  just  sets	the -rfbport option to 5900+N The program will
	      exit immediately if that port is not available.  The  -N	option
	      only  works with normal -display usage, e.g. :0 or :8, -N	is ig-
	      nored in the -display WAIT:..., -create, -find, -svc, -redirect,
	      etc modes.

       -autoport n

	      Automatically  probe for a free VNC port starting	at n.  The de-
	      fault is to start	probing	at 5900.  Use this to stay  away  from
	      other VNC	servers	near 5900.

       -rfbport	str

	      The  VNC	port to	listen on (a LibVNCServer option), e.g.	 5900,
	      5901, etc.  If specified as "-rfbport PROMPT"  then  the	x11vnc
	      -gui is used to prompt the user to enter the port	number.


	      IPv6  listening  support.	 In addition to	IPv4, the IPv6 address
	      is listened on for incoming connections.	The same  port	number
	      as IPv4 is used.

	      NOTE:   This  x11vnc  binary  was	compiled to have the "-6" IPv6
	      listening	mode ENABLED by	default	(CPPFLAGS -DX11VNC_LISTEN6=1).
	      So to disable IPv6 listening mode	you MUST supply	the "-no6" op-
	      tion (see	below.)

	      The "-6" mode works for both normal  connections	and  -ssl  en-
	      crypted ones.  Nearly everything is supported for	the IPv6 case,
	      but there	are a few exceptions.  See -stunnel for	its IPv6  sup-

	      Currently,  for  absolutely everything to	work correctly the ma-
	      chine may	need to	have some IPv4 support,	at the least  for  the
	      loopback interface.  However, for	nearly all usage modes no IPv4
	      support is required. See -noipv4.

	      If you have trouble compiling  or	 running  in  IPv6  mode,  set
	      -DX11VNC_IPV6=0  in  CPPFLAGS  when  configuring to disable IPv6


	      Disable IPv6 listening support (only useful if the "-6" mode  is
	      compiled	in  to be the default; see the X11VNC_LISTEN6 descrip-
	      tion above under "-6".)


	      Do not try to use	IPv6 for any listening or connecting  sockets.
	      This  includes  both  the	listening service port(s) and outgoing
	      connections from -connect,  -connect_or_exit,  or	 -proxy.   Use
	      this if you are having problems due to IPv6.


	      Do  not try to use IPv4 for any listening	or connecting sockets.
	      This is mainly for  exploring  the  behavior  of	x11vnc	on  an
	      IPv6-only	system,	but may	have other uses.


	      If  the X	server connection is disconnected, try to reopen the X
	      display (up to one time.)	 This is of use	for  display  managers
	      like  GDM	 (KillInitClients  option) that	kill x11vnc just after
	      the user logs into the X session.	 Note: the reopened state  may
	      be  unstable.  Set X11VNC_REOPEN_DISPLAY=n to reopen n times and
	      set X11VNC_REOPEN_SLEEP_MAX to the number	 of  seconds,  default
	      10, to keep trying to reopen the display (once per second.)

	      Update:  as  of 0.9.9, x11vnc tries to automatically avoid being
	      killed by	the display manager by delaying	 creating  windows  or
	      using   XFIXES.	 So   you  shouldn't  need  to	use  KillInit-
	      Clients=false as long as you log in quickly  enough  (within  45
	      seconds  of  connecting.)	  You  can  disable  this  by  setting
	      X11VNC_AVOID_WINDOWS=never.  You can also	set it to  the	number
	      of seconds to delay.

       -reflect	host:N

	      Instead  of  connecting  to and polling an X display, connect to
	      the remote VNC server host:N and be a reflector/repeater for it.
	      This  is useful for trying to manage the case of many simultane-
	      ous VNC viewers (e.g. classroom broadcasting)  where,  e.g.  you
	      put  a  repeater on each network switch, etc, to improve perfor-
	      mance by distributing the	load  and  network  traffic.   Implies
	      -shared  (use  -noshared	as a later option to disable). See the
	      discussion below under -rawfb vnc:host:N for more	details.

       -id windowid

	      Show the X window	corresponding to windowid not the entire  dis-
	      play.   New  windows like	popup menus, transient toplevels, etc,
	      may not be seen or may  be  clipped.   Disabling	SaveUnders  or
	      BackingStore  in	the  X	server may help	show them.  x11vnc may
	      crash if the window is  initially	 partially  obscured,  changes
	      size, is iconified, etc.	Some steps are taken to	avoid this and
	      the -xrandr mechanism is used to track resizes.  Use xwininfo(1)
	      to get the window	id, or use "-id	pick" to have x11vnc run xwin-
	      info(1) for you and extract the id.  The -id  option  is	useful
	      for exporting very simple	applications (e.g. the current view on
	      a	webcam).

       -sid windowid

	      As -id, but instead of using the window  directly	 it  shifts  a
	      root view	to it: this shows SaveUnders menus, etc, although they
	      will be clipped if they extend beyond the	window.


	      Simple application sharing based on the -id/-sid mechanism.  Ev-
	      ery  new	toplevel window	that the application creates induces a
	      new viewer window	via a reverse connection.   The	 -id/-sid  and
	      -connect options are required.  Run 'x11vnc -appshare -help' for
	      more info.

       -clip WxH+X+Y

	      Only show	the sub-region of the full display that	corresponds to
	      the  rectangle  geometry with size WxH and offset	+X+Y.  The VNC
	      display has size WxH (i.e. smaller than the full display).  This
	      also works for -id/-sid mode where the offset is relative	to the
	      upper left corner	of the selected	window.	  An  example  use  of
	      this  option  would  be to split a large (e.g. Xinerama) display
	      into two parts to	be accessed via	separate viewers by running  a
	      separate x11vnc on each part.

	      Use  '-clip  xinerama0' to clip to the first xinerama sub-screen
	      (if xinerama is active).	xinerama1 for the 2nd sub-screen, etc.
	      This way you don't need to figure	out the	WxH+X+Y	of the desired
	      xinerama sub-screen.  screens are	sorted in increasing  distance
	      from the (0,0) origin (I.e. not the Xserver's order).


	      In  8bpp	indexed	color, let the installed colormap flash	as the
	      pointer moves from window	to window (slow).  Also	try the	-8to24
	      option to	avoid flash altogether.

       -shiftcmap n

	      Rare  problem,  but  some	8bpp displays use less than 256	color-
	      cells (e.g. 16-color grayscale, perhaps the other	bits are  used
	      for double buffering) *and* also need to shift the pixels	values
	      away from	0, .., ncells.	n indicates the	shift to be applied to
	      the  pixel  values.  To see the pixel values set DEBUG_CMAP=1 to
	      print out	a colormap histogram.  Example:	-shiftcmap 240


	      For 8bpp displays, force indexed color (i.e. a colormap) even if
	      it looks like 8bpp TrueColor (rare problem).


	      If  the  X11  display is indexed color, lie to clients when they
	      first connect by telling them it is  truecolor.	To  workaround
	      RealVNC:	inPF  has colourMap but	not 8bpp Use '-advertise_true-
	      color reset' to reset client fb too.

       -visual n

	      This option probably does	not do	what  you  think.   It	simply
	      *forces*	the visual used	for the	framebuffer; this may be a bad
	      thing... (e.g. messes up colors or cause a crash). It is	useful
	      for  testing  and	for some workarounds.  n may be	a decimal num-
	      ber, or 0x hex.  Run xdpyinfo(1) for the values.	One  may  also
	      use  "TrueColor",	 etc. see <X11/X.h> for	a list.	 If the	string
	      ends in ":m" then	for better or for worse	the  visual  depth  is
	      forced  to be m.	You may	want to	use -noshm when	using this op-
	      tion (so XGetImage may automatically translate the pixel data).


	      Handle multiple depth visuals on one screen, e.g.	8+24 and  24+8
	      overlay  visuals	(the  32  bits per pixel are packed with 8 for
	      PseudoColor and 24 for TrueColor).

	      Currently	-overlay only works on Solaris	via  XReadScreen(3X11)
	      and  IRIX	 using XReadDisplay(3).	 On Solaris there is a problem
	      with image "bleeding" around transient popup menus (but not  for
	      the menu itself):	a workaround is	to disable SaveUnders by pass-
	      ing the "-su" argument to	Xsun (in /etc/dt/config/Xservers).

	      Use -overlay as a	workaround for	situations  like  these:  Some
	      legacy  applications  require  the  default  visual  to  be 8bpp
	      (8+24), or they will use 8bpp PseudoColor	even when the  default
	      visual  is  depth	24 TrueColor (24+8).  In these cases colors in
	      some windows will	be incorrect  in  x11vnc  unless  -overlay  is
	      used.   Another  use  of -overlay	is to enable showing the exact
	      mouse cursor shape (details below).

	      Under -overlay, performance will be somewhat slower due  to  the
	      extra  image  transformations required.  For optimal performance
	      do not use -overlay, but rather configure	the X server  so  that
	      the  default  visual  is	depth 24 TrueColor and try to have all
	      apps use that visual (e.g. some apps have	-use24 or -visual  op-


	      Sets  -overlay,  but does	not try	to draw	the exact mouse	cursor
	      shape using the overlay mechanism.

       -8to24 [opts]

	      Try this option if -overlay is not supported on your OS, and you
	      have  a  legacy  8bpp app	that you want to view on a multi-depth
	      display with default depth 24 (and is 32 bpp) OR have a  default
	      depth  8	display	 with  depth 24	overlay	windows	for some apps.
	      This option may not work on all X	servers	and  hardware  (tested
	      on  XFree86/Xorg mga driver and Xsun).  The "opts" string	is not
	      required and is described	below.

	      This mode	enables	a hack where x11vnc monitors windows within  3
	      levels  from  the	root window.  If it finds any that are 8bpp it
	      extracts the indexed color pixel values  using  XGetImage()  and
	      then  applies  a	transformation using the colormap(s) to	create
	      TrueColor	RGB values that	it in turn inserts into	bits  1-24  of
	      the  framebuffer.	 This creates a	depth 24 "view"	of the display
	      that is then exported via	VNC.

	      Conversely, for default depth 8 displays,	the depth  24  regions
	      are  read	 by  XGetImage() and everything	is transformed and in-
	      serted into a depth 24 TrueColor framebuffer.

	      Note that	even if	there are *no* depth  24  visuals  or  windows
	      (i.e.  pure  8bpp), this mode is potentially an improvement over
	      -flashcmap because it avoids the flashing	and shows each	window
	      in the correct color.

	      This  method  works  OK, but may still have bugs and it does hog
	      resources.  If there are multiple	8bpp windows  using  different
	      colormaps, one may have to iconify all but one for the colors to
	      be correct.

	      There may	be painting errors for clipping	and switching  between
	      windows  of  depths  8 and 24.  Heuristics are applied to	try to
	      minimize the painting errors.  One can also press	3 Alt_L's in a
	      row  to  refresh the screen if the error does not	repair itself.
	      Also the option -fixscreen 8=3.0 or -fixscreen V=3.0 may be used
	      to periodically refresh the screen at the	cost of	bandwidth (ev-
	      ery 3 sec	for this example).

	      The [opts] string	can contain the	following settings.   Multiple
	      settings are separated by	commas.

	      For  for	some  X	servers	with default depth 24 a	speedup	may be
	      achieved via the option "nogetimage".   This  enables  a	scheme
	      were  XGetImage()	 is  not  used to retrieve the 8bpp data.  In-
	      stead, it	assumes	that the 8bpp data is in  bits	25-32  of  the
	      32bit  X	pixels.	  There	 is  no	 requirement that the X	server
	      should put the data there	for our	poll requests, but some	do and
	      so  the  extra steps to retrieve it can be skipped.  Tested with
	      mga driver with XFree86/Xorg.  For the default depth 8 case this
	      option is	ignored.

	      To  adjust how often XGetImage() is used to poll the non-default
	      visual regions for changes, use the option "poll=t" where	"t" is
	      a	floating point time.  (default:	0.05)

	      Setting  the  option  "level2" will limit	the search for non-de-
	      fault visual windows to two levels from  the  root  window.   Do
	      this on slow machines where you know the window manager only im-
	      poses one	extra window between the app window and	the root  win-

	      Also for very slow machines use "cachewin=t" where t is a	float-
	      ing point	amount of time to cache	XGetWindowAttributes  results.
	      E.g. cachewin=5.0.  This may lead	to the windows being unnoticed
	      for this amount of time when deiconifying, painting errors, etc.

	      While testing on a very old SS20 these  options  gave  tolerable
	      response:	 -8to24	poll=0.2,cachewin=5.0. For this	machine	-over-
	      lay is supported and gives better	response.

	      Debugging	for this mode  can  be	enabled	 by  setting  "dbg=1",
	      "dbg=2", or "dbg=3".


	      Very  rare  problem: if the framebuffer (X display or -rawfb) is
	      24bpp instead of the usual 32bpp,	then dynamically transform the
	      pixels  to  32bpp.  This will be slower, but can be used to work
	      around problems where VNC	 viewers  cannot  handle  24bpp	 (e.g.
	      "main:  setPF:  not  8,  16  or 32 bpp?").  See the FAQ for more

	      In the case of -rawfb mode, the pixels are directly modified  by
	      inserting	 a 0 byte to pad them out to 32bpp.  For X displays, a
	      kludge is	done that  is  equivalent  to  "-noshm	-visual	 True-
	      Color:32".   (If	better	performance  is	needed for the latter,
	      feel free	to ask).

       -scale fraction

	      Scale the	framebuffer by factor fraction.	 Values	 less  than  1
	      shrink the fb, larger ones expand	it. Note: the image may	not be
	      sharp and	response may be	slower.	 If fraction contains a	 deci-
	      mal  point  "." it is taken as a floating	point number, alterna-
	      tively the notation "m/n"	may be used to	denote	fractions  ex-
	      actly, e.g. -scale 2/3

	      To  scale	 asymmetrically	 in the	horizontal and vertical	direc-
	      tions, specify a	WxH  geometry  to  stretch  to:	 e.g.  '-scale
	      1024x768', or also '-scale 0.9x0.75'

	      Scaling  Options:	can be added after fraction via	":", to	supply
	      multiple ":" options use commas.	If  you	 just  want  a	quick,
	      rough  scaling  without blending,	append ":nb" to	fraction (e.g.
	      -scale 1/3:nb).  No blending is the  default  for	 8bpp  indexed
	      color, to	force blending for this	case use ":fb".

	      To  disable  -scrollcopyrect  and	-wirecopyrect under -scale use
	      ":nocr".	If you need to to enable them  use  ":cr"  or  specify
	      them  explicitly	on  the	 command  line.	 If a slow link	is de-
	      tected, ":nocr" may be applied automatically.  Default: :cr

	      More esoteric options: for  compatibility	 with  vncviewers  the
	      scaled  width is adjusted	to be a	multiple of 4: to disable this
	      use ":n4".  ":in"	use interpolation scheme even when  shrinking,
	      ":pad"  pad  scaled  width and height to be multiples of scaling
	      denominator (e.g.	3 for 2/3).

       -geometry WxH

	      Same as -scale WxH

       -scale_cursor frac

	      By default if -scale is supplied the cursor shape	is  scaled  by
	      the same factor.	Depending on your usage, you may want to scale
	      the cursor independently of the screen or	not at	all.   If  you
	      specify  -scale_cursor the cursor	will be	scaled by that factor.
	      When using -scale	mode to	keep the cursor	at its "natural"  size
	      use  "-scale_cursor  1".	 Most of the ":" scaling options apply
	      here as well.


	      All VNC clients can only watch (default off).


	      VNC display is shared, i.e. more than one	viewer can connect  at
	      the same time (default off).


	      Exit  after the first successfully connected viewer disconnects,
	      opposite of -forever. This is the	Default.


	      Keep listening for more connections rather than exiting as  soon
	      as the first client(s) disconnect. Same as -many

	      To get the standard non-shared VNC behavior where	when a new VNC
	      client connects the existing VNC client is dropped use:  -never-
	      shared  -forever	 This method can also be used to guard against
	      hung TCP connections that	do not go away.


	      Create an	outer loop restarting the x11vnc process  whenever  it
	      terminates.   -bg	 and  -inetd are ignored in this mode (however
	      see -loopbg below).

	      Useful for continuing  even  if  the  X  server  terminates  and
	      restarts (at that	moment the process will	need permission	to re-
	      connect to the new X server of course).

	      Use, e.g., -loop100 to sleep  100	 millisecs  between  restarts,
	      etc.   Default  is  2000ms (i.e. 2 secs) Use, e.g. -loop300,5 to
	      sleep 300	ms and only loop 5 times.

	      If -loopbg (plus any numbers) is specified  instead,  the	 "-bg"
	      option  is  implied  and the mode	approximates inetd(8) usage to
	      some degree.  In this case when it goes into the background  any
	      listening	 sockets  (i.e.	 ports	5900, 5800) are	closed,	so the
	      next one in the loop can use them.  This mode will  only	be  of
	      use  if  a  VNC client (the only client for that process)	is al-
	      ready connected before the process goes into the background, for
	      example,	usage of -display WAIT:.., -svc, and -connect can make
	      use of this "poor	man's" inetd mode.  The	default	wait  time  is
	      500ms  in	 this  mode.   This  usage could use useful:  -svc -bg

       -timeout	n

	      Exit unless a client connects within the first n	seconds	 after

	      If there have been no connection attempts	after n	seconds	x11vnc
	      exits immediately.  If a client is trying	to connect but has not
	      progressed  to the normal	operating state, x11vnc	gives it a few
	      more seconds to finish and exits if it does not make it  to  the
	      normal state.

	      For reverse connections via -connect or -connect_or_exit a time-
	      out of n seconds will be set for all reverse connects.   If  the
	      connect timeout alarm goes off, x11vnc will exit immediately.

       -sleepin	n

	      At  startup  sleep  n  seconds  before proceeding	(e.g. to allow
	      redirs and listening clients to start up)

	      If a range is given: '-sleepin min-max', a random	value  between
	      min and max is slept. E.g. '-sleepin 0-20' and '-sleepin 10-30'.
	      Floats are allowed too.


	      Launched by inetd(8): stdio instead of listening socket.	 Note:
	      if you are not redirecting stderr	to a log file (via shell 2> or
	      -o option) you MUST also specify the -q  option,	otherwise  the
	      stderr  goes to the viewer which will cause it to	abort.	Speci-
	      fying both -inetd	and -q and no -o will automatically close  the


	      Enable the TightVNC file transfer	extension. Note	that that when
	      the -viewonly option is supplied all  file  transfers  are  dis-
	      abled.  Also clients that	log in viewonly	cannot transfer	files.
	      However, if the remote control mechanism is used to  change  the
	      global or	per-client viewonly state the filetransfer permissions
	      will NOT change.

	      IMPORTANT: please	understand if -tightfilexfer is	specified  and
	      you  run x11vnc as root for, say,	inetd or display manager (gdm,
	      kdm, ...)	access and you do not have it  switch  users  via  the
	      -users  option,  then  VNC  Viewers  that	connect	are able to do
	      filetransfer reads and writes as *root*.

	      Also, tightfilexfer is disabled in -unixpw mode.


	      Note: to enable UltraVNC filetransfer and	to get it to work  you
	      probably need to supply these LibVNCServer options: "-rfbversion
	      3.6 -permitfiletransfer" "-ultrafilexfer"	is an alias  for  this

	      IMPORTANT:  please understand if -ultrafilexfer is specified and
	      you run x11vnc as	root for, say, inetd or	display	manager	 (gdm,
	      kdm,  ...)  access  and  you do not have it switch users via the
	      -users option, then VNC Viewers that  connect  are  able	to  do
	      filetransfer reads and writes as *root*.

	      Note  that  sadly	 you cannot do both -tightfilexfer and -ultra-
	      filexfer at the same time	because	the  latter  requires  setting
	      the version to 3.6 and tightvnc will not do filetransfer when it
	      sees that	version	number.


	      Instead of using -httpdir	(see below) to specify where the  Java
	      vncviewer	applet is, have	x11vnc try to *guess* where the	direc-
	      tory is by looking relative to the program location and in stan-
	      dard  locations  (/usr/local/share/x11vnc/classes,  etc).	 Under
	      -ssl or -stunnel the ssl classes subdirectory is sought.


	      As -http,	but force lookup for ssl classes subdir.

	      Note that	for HTTPS, single-port Java applet  delivery  you  can
	      set X11VNC_HTTPS_DOWNLOAD_WAIT_TIME to the max number of seconds
	      to wait for the applet download to finish.  The default is 15.


	      Use the Avahi/mDNS  ZeroConf  protocol  to  advertise  this  VNC
	      server  to  the  local network. (Related terms: Rendezvous, Bon-
	      jour).  Depending	on your	setup, you may need  to	 start	avahi-
	      daemon and open udp port 5353 in your firewall.

	      You   can	  set	X11VNC_AVAHI_NAME,  X11VNC_AVAHI_HOST,	and/or
	      X11VNC_AVAHI_PORT	environment variables to override the  default
	      values.  For example: -env X11VNC_AVAHI_NAME=wally

	      If the avahi API cannot be found at build	time, a	helper program
	      like avahi- publish(1) or	dns- sd(1) will	be tried


	      Same as -avahi.


	      Same as -avahi.

       -connect	string

	      For use with "vncviewer -listen" reverse connections.  If	string
	      has  the	form "host" or "host:port" the connection is made once
	      at startup.

	      Use commas for a list of host's and host:port's.	E.g.  -connect
	      host1,host2 or host1:0,host2:5678.  Note that to reverse connect
	      to multiple hosts	at the same time you will likely need to  also
	      supply: -shared

	      Note  that  unlike most vnc servers, x11vnc will require a pass-
	      word for reverse as well as for forward connections.   (provided
	      password	auth  has  been	 enabled, -rfbauth, etc) If you	do not
	      want  to	require	 a  password  for  reverse   connections   set
	      X11VNC_REVERSE_CONNECTION_NO_AUTH=1  in  your environment	before
	      starting x11vnc.

	      If string	contains "/" it	is instead interpreted as  a  file  to
	      periodically  check  for	new hosts.  The	first line is read and
	      then the file is truncated.  Be careful about  the  location  of
	      this file	if x11vnc is running as	root (e.g. via gdm(1) ,	etc).

	      Repeater	mode:  Some  services provide an intermediate "vnc re-
	      peater":   (and	  also  for  linux  port)  that  acts	 as  a
	      proxy/gateway.  Modes like these require an initial string to be
	      sent  for	 the  reverse  connection  before  the VNC protocol is
	      started.	Here are the ways to do	this:

	      -connect		 pre=some_string+host:port	      -connect
	      pre128=some_string+host:port -connect repeater=ID:1234+host:port
	      -connect repeater=

	      SSVNC notation is	also supported:

	      -connect repeater://host:port+ID:1234

	      As with normal -connect usage, if	the repeater port is not  sup-
	      plied 5500 is assumed.

	      The  basic  idea is between the special tag, e.g.	"pre=" and "+"
	      is the pre-string	to be sent.  Note that in this case  host:port
	      is  the  repeater	 server, NOT the vnc viewer.  Somehow the pre-
	      string tells the repeater	server how to find the vnc viewer  and
	      connect you to it.

	      In  the  case pre=some_string+host:port, "some_string" is	simply
	      sent. In the case	preNNN=some_string+host:port "some_string"  is
	      sent  in	a  null	padded buffer of length	NNN.  repeater=	is the
	      same as pre250=, this is the ultravnc repeater buffer size.

	      Strings like "\n"	and "\r", etc. are  expanded  to  newline  and
	      carriage	return.	  "\c"	is  expanded  to "," since the connect
	      string is	comma separated.

	      See also the -proxy option below for additional  ways  to	 plumb
	      reverse connections.

	      Reverse  SSL: using -connect in -ssl mode	makes x11vnc act as an
	      SSL client (initiates SSL	connection) rather than	an SSL server.
	      The  idea	is x11vnc might	be connecting to stunnel on the	viewer
	      side with	the viewer in listening	mode.  If you do not want this
	      behavior,	 use -env X11VNC_DISABLE_SSL_CLIENT_MODE=1.  With this
	      the viewer side can act as the SSL client	as  it	normally  does
	      for forward connections.

	      Reverse SSL Repeater mode:  This will work, but note that	if the
	      VNC Client does any sort of a 'Fetch Cert'  action  before  con-
	      necting,	then  the Repeater will	likely drop the	connection and
	      both sides will need to restart.	 Consider  the	use  of	 -con-
	      nect_or_exit and -loop300,2 to have x11vnc reconnect once	to the
	      repeater after the fetch.	 You will probably also	want to	supply
	      -sslonly	to  avoid  x11vnc thinking the delay in	response means
	      the  connection  is   VeNCrypt.	 The   env   var   X11VNC_DIS-
	      ABLE_SSL_CLIENT_MODE=1  discussed	above may also be useful (i.e.
	      the viewer can do	a forward connection as	it normally does.)

	      IPv6: as of x11vnc 0.9.10	the -connect option should connect  to
	      IPv6 hosts properly.  If there are problems you can disable IPv6
	      by setting -DX11VNC_IPV6=0 in  CPPFLAGS  when  configuring.   If
	      there  problems  connecting  to IPv6 hosts consider a relay like
	      the included inet6to4 script or the -proxy option.

       -connect_or_exit	str

	      As with -connect,	except if none of the reverse connections suc-
	      ceed, then x11vnc	shuts down immediately

	      An easier	to type	alias for this option is '-coe'

	      By the way, if you do not	want x11vnc to listen on ANY interface
	      use -rfbport 0  which is handy for the -connect_or_exit mode.

       -proxy string

	      Use proxy	in string (e.g.	host:port) as a	proxy for  making  re-
	      verse connections	(-connect or -connect_or_exit options).

	      Web proxies are supported, but note by default most of them only
	      support destination connections to ports 443  or	563,  so  this
	      might  not  be  very  useful (the	viewer would need to listen on
	      that port	or the router would have to do a port redirection).

	      A	 web  proxy  may  be  specified	 by  either   "host:port"   or
	      "http://host:port"  (the port is required	even if	it is the com-
	      mon choices 80 or	8080)

	      SOCKS4, SOCKS4a, and SOCKS5 are also supported.	SOCKS  proxies
	      normally	do  not	have restrictions on the destination port num-

	      Use a format like	this: socks://host:port	or socks5://host:port.
	      Note  that  ssh  -D  does	not support SOCKS4a, so	use socks5://.
	      For socks:// SOCKS4 is used on a numerical IP  and  "localhost",
	      otherwise	 SOCKS4a is used (and so the proxy tries to do the DNS

	      An experimental mode is "-proxy http://host:port/..."  Note  the
	      "/"  after  the  port  that  distinguishes  it from a normal web
	      proxy.  The port must be supplied	even if	it is the default  80.
	      For  this	mode a GET is done to the supplied URL with the	string
	      host=H&port=P appended.  H and P will be	the  -connect  reverse
	      connect  host and	port.  Use the string "__END__"	to disable the
	      appending.  The basic idea here is that maybe  some  cgi	script
	      provides	the actual viewer hookup and tunnelling.  How to actu-
	      ally achieve this	within cgi, php, etc. is not clear...  A  cus-
	      tom web server or	apache module would be straight-forward.

	      Another  experimental  mode is "-proxy ssh://user@host" in which
	      case a SSH tunnel	is used	for  the  proxying.   "user@"  is  not
	      needed  unless your unix username	is different on	"host".	 For a
	      non-standard SSH port use	ssh://user@host:port.  If proxies  are
	      chained  (see next paragraph) then the ssh one must be the first
	      one.  If ssh-agent is not	active,	then the ssh password needs to
	      be entered in the	terminal where x11vnc is running.  Examples:

	      -connect localhost:0 -proxy ssh://me@friends-pc:2222

	      -connect snoopy:0	-proxy ssh://

	      Multiple	proxies	 may  be chained together in case one needs to
	      ricochet off of a	number of  hosts  to  finally  reach  the  VNC
	      viewer.	Up to 3	may be chained,	separate them by commas	in the
	      order    they    are    to    be	  connected	to.	 E.g.:
	      http://host1:port1,socks5://host2:port2	  or	three	 like:

	      IPv6: as of x11vnc 0.9.10	the -proxy option  should  connect  to
	      IPv6 hosts properly.  If there are problems you can disable IPv6
	      by setting -DX11VNC_IPV6=0 in  CPPFLAGS  when  configuring.   If
	      there  problems  connecting  to IPv6 hosts consider a relay like
	      the included inet6to4 script.

       -vncconnect, -novncconnect

	      Monitor the VNC_CONNECT X	property set by	the standard VNC  pro-
	      gram  vncconnect(1).   When  the	property  is  set to "host" or
	      "host:port" establish a reverse connection.  Using xprop(1)  in-
	      stead of vncconnect may work (see	the FAQ).  The -remote control
	      mechanism	uses  X11VNC_REMOTE  channel,  and  this  option  dis-
	      ables/enables it as well.	 Default: -vncconnect

	      To  use  different  names	for these X11 properties (e.g. to have
	      separate communication channels for  multiple  x11vnc's  on  the
	      same display) set	the VNC_CONNECT	or X11VNC_REMOTE env. vars. to
	      the string you want, for example:	-env  X11VNC_REMOTE=X11VNC_RE-
	      MOTE_12345  Both	sides  of the channel must use the same	unique
	      name.  The same can be done for the internal X11VNC_TICKER prop-
	      erty (heartbeat and timestamp) if	desired.

       -allow host1[,host2..]

	      Only allow client	connections from hosts matching	the comma sep-
	      arated list of hostnames or IP addresses.	 Can also be a numeri-
	      cal  IP  prefix,	e.g. "192.168.100."  to	match a	simple subnet,
	      for more control build LibVNCServer with	libwrap	 support  (See
	      the  FAQ).   If  the  list contains a "/"	it instead is a	inter-
	      preted as	a file containing addresses or prefixes	 that  is  re-
	      read  each  time	a new client connects.	Lines can be commented
	      out with the "#" character in the	usual way.

	      -allow applies in	-ssl mode, but not in -stunnel mode.

	      IPv6: as of x11vnc 0.9.10	a host can be specified	in IPv6	numer-
	      ical format, e.g.	2001:4860:b009::93.


	      Basically	the same as "-allow".

	      Note:  if	 you  want  to restrict	which network interface	x11vnc
	      listens on, see the -listen option below.	 E.g. "-listen	local-
	      host"  or	"-listen".	 As a special case, the	option
	      "-localhost" implies "-listen localhost".

	      A	rare case, but for non-localhost -listen usage,	if you use the
	      remote  control  mechanism  (-R) to change the -listen interface
	      you may need to manually adjust the -allow list (and vice	versa)
	      to  avoid	 situations where no connections (or too many) are al-

	      If you do	not want x11vnc	to listen on ANY interface  (evidently
	      you  are	using -connect or -connect_or_exit, or plan to use re-
	      mote control: -R connect:host), use -rfbport 0

	      IPv6: if IPv6 is supported, this	option	automatically  implies
	      the IPv6 loopback	address	'::1' as well.

       -unixsock str

	      Listen on	the unix socket	(AF_UNIX) 'str'	for connections.  This
	      mode is for either local connections or a	tunnel endpoint	 where
	      one  wants the file permission of	the unix socket	file to	deter-
	      mine what	can connect to it.  (This currently requires  an  edit
	      to  libvnserver/rfbserver.c:  comment  out  lines	 310  and 311,
	      'close(sock)' and	'return	NULL' in rfbserver.c  after  the  set-
	      sockopt()	 call.)	 Note  that to disable all tcp listening ports
	      specify '-rfbport	0' and should be useful	with this mode.	 Exam-
	      ple: mkdir ~/s; chmod 700	~/s; x11vnc -unixsock ~/s/mysock -rfb-
	      port 0 ...  The SSVNC unix vncviewer can connect to  unix	 sock-

       -listen6	str

	      When in IPv6 listen mode "-6", listen only on the	network	inter-
	      face with	address	str.  It also works for	link  scope  addresses
	      (fe80::219:dbff:fee5:3f92%eth0)  and IPv6	hostname strings (e.g.	 Use LibVNCServer -listen option for the  IPv4


	      Do  not  use  gethostbyname() or gethostbyaddr() to look up host
	      names or IP numbers.  Use	this if	name resolution	is incorrectly
	      set up and leads to long pauses as name lookups time out,	etc.

       -input string

	      Fine tuning of allowed user input.  If string does not contain a
	      comma ","	the tuning applies only	to normal clients.   Otherwise
	      the part before "," is for normal	clients	and the	part after for
	      view-only	clients.  "K" is for Keystroke input, "M"  for	Mouse-
	      motion  input,  "B" for Button-click input, "C" is for Clipboard
	      input, and "F" is	for  File  transfer  (ultravnc	only).	 Their
	      presence in the string enables that type of input.  E.g. "-input
	      M" means normal users can	only move the mouse and	  "-input  KM-
	      BCF,M" lets normal users do anything and enables view-only users
	      to move the  mouse.   This  option  is  ignored  when  a	global
	      -viewonly	is in effect (all input	is discarded in	that case).


	      When VNC viewers are connected, attempt to the grab the keyboard
	      so a (non-malicious) user	sitting	at the physical	display	is not
	      able  to enter keystrokes.  This method uses XGrabKeyboard(3X11)
	      and so it	is not secure and does not rule	out the	person at  the
	      physical	display	 injecting  keystrokes	by flooding the	server
	      with them, grabbing the keyboard himself,	etc.  Some  degree  of
	      cooperation  from	the person at the display is assumed.  This is
	      intended for remote help-desk or educational usage modes.

	      Note: on	some  recent  (12/2010)	 X  servers  and/or  desktops,
	      -grabkbd	no  longer  works: it prevents the window manager from
	      resizing windows and  similar  things.   Try  -ungrabboth	 below
	      (might not work.)


	      As -grabkbd, but for the mouse pointer using XGrabPointer(3X11).
	      Unfortunately due	to the way the X server	works, the  mouse  can
	      still  be	 moved around by the user at the physical display, but
	      he will not be able to change window focus with it.   Also  some
	      window  managers	that  call XGrabServer(3X11) for resizes, etc,
	      will act on the local user's input.  Again, some degree of coop-
	      eration from the person at the display is	assumed.


	      Whenever there is	any input (either keyboard or pointer),	ungrab
	      *both* the keyboard and the pointer  while  injecting  the  syn-
	      thetic  input.   This is to allow	window managers, etc. a	chance
	      to grab.


	      Apply both -grabkbd and -grabptr even when no  VNC  viewers  are
	      connected.  If you only want one of them,	use the	-R remote con-
	      trol to turn the other back on, e.g. -R nograbptr.

       -viewpasswd string

	      Supply a 2nd password for	view-only logins.  The -passwd	(full-
	      access) password must also be supplied.

       -passwdfile filename

	      Specify the LibVNCServer password	via the	first line of the file
	      filename (instead	of via -passwd on the command line where  oth-
	      ers might	see it via ps(1) ).

	      See the descriptions below for how to supply multiple passwords,
	      view-only	passwords, to specify external programs	 for  the  au-
	      thentication, and	other features.

	      If  the filename is prefixed with	"rm:" it will be removed after
	      being read.  Perhaps this	is useful in limiting the  readability
	      of  the file.  In	general, the password file should not be read-
	      able by untrusted	users (BTW: neither should  the	 VNC  -rfbauth
	      file: it is NOT encrypted, only obscured with a fixed key).

	      If the filename is prefixed with "read:" it will periodically be
	      checked for changes and reread.  It is guaranteed	to  be	reread
	      just  when  a  new  client connects so that the latest passwords
	      will be used.

	      If filename is prefixed with "cmd:" then the  string  after  the
	      ":"  is  run  as	an external command: the output	of the command
	      will be interpreted as if	it were	read from a password file (see
	      below).  If the command does not exit with 0, then x11vnc	termi-
	      nates immediately.  To specify more than 1000 passwords this way
	      set  X11VNC_MAX_PASSWDS before starting x11vnc.  The environment
	      variables	are set	as in -accept.

	      Note that	due to the VNC protocol	only the first 8 characters of
	      a	password are used (DES key).

	      If  filename  is	prefixed with "custom:"	then a custom password
	      checker is supplied as an	external command  following  the  ":".
	      The  command  will  be  run when a client	authenticates.	If the
	      command exits with 0 the client is accepted, otherwise it	is re-
	      jected.  The environment variables are set as in -accept.

	      The standard input to the	custom command will be a decimal digit
	      "len" followed by	a newline. "len" specifies the challenge  size
	      and  is usually 16 (the VNC spec).  Then follows len bytes which
	      is the random challenge string that was sent to the client. This
	      is then followed by len more bytes holding the client's response
	      (i.e. the	challenge string encrypted via DES with	the user pass-
	      word in the standard situation).

	      The  "custom:"  scheme  can be useful to implement dynamic pass-
	      words or to implement methods where longer passwords and/or dif-
	      ferent  encryption algorithms are	used.  The latter will require
	      customizing the VNC client as well.  One could create an	MD5SUM
	      based scheme for example.

	      File format for -passwdfile:

	      If multiple non-blank lines exist	in the file they are all taken
	      as valid passwords.  Blank lines are  ignored.   Password	 lines
	      may  be "commented out" (ignored)	if they	begin with the charac-
	      ter "#" or the line contains the string "__SKIP__".   Lines  may
	      be annotated by use of the "__COMM__" string: from it to the end
	      of the line is ignored.  An empty	password may be	specified  via
	      the  "__EMPTY__"	string	on  a line by itself (note your	viewer
	      might not	accept empty passwords).

	      If the string "__BEGIN_VIEWONLY__" appears on a line by  itself,
	      the  remaining passwords are used	for viewonly access.  For com-
	      patibility, as a special case if	the  file  contains  only  two
	      password	lines  the  2nd	 one  is  automatically	 taken	as the
	      viewonly password.   Otherwise  the  "__BEGIN_VIEWONLY__"	 token
	      must be used to have viewonly passwords.	(tip: make the 3rd and
	      last line	be "__BEGIN_VIEWONLY__"	to have	 2  full-access	 pass-

       -showrfbauth filename

	      Print  to	 the  screen the obscured VNC password kept in the rf-
	      bauth file filename and then exit.

       -unixpw [list]

	      Use Unix username	and password authentication.  x11vnc will  use
	      the  su(1)  program to verify the	user's password.  [list] is an
	      optional comma separated list of allowed Unix usernames.	If the
	      [list] string begins with	the character "!" then the entire list
	      is taken as an exclude list.  See	 below	for  per-user  options
	      that can be applied.

	      A	 familiar  "login:" and	"Password:" dialog is presented	to the
	      user on a	black screen inside the	vncviewer.  The	connection  is
	      dropped  if  the	user fails to supply the correct password in 3
	      tries or does not	send one before	a 45 second timeout.  Existing
	      clients are view-only during this	period.

	      If  the first character received is "Escape" then	the unix user-
	      name will	not be displayed after "login:"	as it is typed.	  This
	      could  be	 of  use  for  VNC viewers that	automatically type the
	      username and password.

	      Since the	detailed behavior of su(1) can vary from OS to OS  and
	      for  local  configurations,  test	 the mode before deployment to
	      make sure	it is working properly.	 x11vnc	 will  attempt	to  be
	      conservative and reject a	login if anything abnormal occurs.

	      One  case	 to note: FreeBSD and the other	BSD's by default it is
	      impossible for the user running x11vnc  to  validate  his	 *own*
	      password	via  su(1)  (commenting	 out  the entry in
	      /etc/pam.d/su eliminates this behavior).	So  the	 x11vnc	 login
	      will always *FAIL* for this case (even when the correct password
	      is supplied).

	      A	possible workaround for	this on	*BSD would be to start	x11vnc
	      as  root	with the "-users +nobody" option to immediately	switch
	      to user nobody where the su'ing will proceed normally.

	      Another source of	potential problems are PAM modules that	prompt
	      for  extra info, e.g. password aging modules.  These logins will
	      fail as well even	when the correct password is supplied.

	      **IMPORTANT**: to	prevent	the Unix password being	sent in	*clear
	      text*  over the network, one of two schemes will be enforced: 1)
	      the -ssl builtin SSL mode, or 2)	require	 both  -localhost  and
	      -stunnel be enabled.

	      Method  1)  ensures  the traffic is encrypted between viewer and
	      server.  A PEM file will be required, see	the  discussion	 under
	      -ssl  below (under some circumstances a temporary	one can	be au-
	      tomatically generated).

	      Method 2)	requires the viewer connection to appear to come  from
	      the  same	 machine x11vnc	is running on (e.g. from a ssh -L port
	      redirection).  And that the -stunnel SSL mode be	used  for  en-
	      cryption	over the network. (see the description of -stunnel be-

	      Note: as a convenience, if you ssh(1) in	and  start  x11vnc  it
	      will check if the	environment variable SSH_CONNECTION is set and
	      appears reasonable.  If it does, then the	-ssl or	 -stunnel  re-
	      quirement	 will be dropped since it is assumed you are using ssh
	      for the encrypted	tunnelling.   -localhost  is  still  enforced.
	      Use  -ssl	 or -stunnel to	force SSL usage	even if	SSH_CONNECTION
	      is set.

	      To override the above restrictions you can set environment vari-
	      ables before starting x11vnc:

	      Set  UNIXPW_DISABLE_SSL=1	 to  disable  requiring	either -ssl or
	      -stunnel (as under SSH_CONNECTION.)  Evidently you will be using
	      a	different method to encrypt the	data between the vncviewer and
	      x11vnc: perhaps ssh(1) or	an IPSEC VPN. -localhost is still  en-
	      forced (however, see the next paragraph.)

	      Set  UNIXPW_DISABLE_LOCALHOST=1  to  disable  the	-localhost re-
	      quirement	in -unixpw modes.  One should never do this (i.e.  al-
	      low the Unix passwords to	be sniffed on the network.)  This also
	      disables the localhost requirement for reverse connections  (see

	      Note  that  use  of  -localhost  with ssh(1) (and	no -unixpw) is
	      roughly the same as requiring a Unix user	login  (since  a  Unix
	      password or the user's public key	authentication is used by sshd
	      on the machine where x11vnc runs and only	local connections from
	      that machine are accepted).

	      Regarding	reverse	connections (e.g. -R connect:host and -connect
	      host), when the -localhost constraint is in effect then  reverse
	      connections  can	only  be  used	to connect to the same machine
	      x11vnc is	running	on (default port 5500).	 Please	use a  ssh  or
	      stunnel port redirection to the viewer machine to	tunnel the re-
	      verse connection over an encrypted channel.

	      In -inetd	mode the Method	1) will	be enforced  (not  Method  2).
	      With  -ssl  in  effect reverse connections are disabled.	If you
	      override this via	env. var, be sure to also use encryption  from
	      the  viewer  to  inetd.  Tip: you	can also have your own stunnel
	      spawn x11vnc in -inetd mode (thereby bypassing inetd).  See  the
	      FAQ for details.

	      The  user	 names in the comma separated [list] may have per-user
	      options after a ":", e.g.	"fred:opts" where "opts" is a "+" sep-
	      arated   list  of	 "viewonly",  "fullaccess",  "input=XXXX",  or
	      "deny", e.g. "karl,wally:viewonly,boss:input=M".	 For  "input="
	      it is the	K,M,B,C	described under	-input.

	      If  an item in the list is "*" that means	those options apply to
	      all users.  It ALSO implies all users are	allowed	to log in  af-
	      ter  supplying  a	valid password.	 Use "deny" to explicitly deny
	      some users if you	use "*"	to set a global	option.	 If [list] be-
	      gins  with the "!" character then	"*" is ignored for checking if
	      the user is allowed, but the option values associated with it do
	      apply as normal.

	      There  are  also some utilities for checking passwords if	[list]
	      starts with the "%" character.  See the quick_pw() function  for
	      more details.  Description: "%-" or "%stdin" means read one line
	      from stdin.  "%env" means	it is in $UNIXPW env var.   A  leading
	      "%/"  or	"%."  means read the first line	from the filename that
	      follows after the	% character. % by itself means prompt for  the
	      username	and  password.	 Otherwise:  %user:pass	  E.g. -unixpw
	      %fred:swordfish For the other cases user:pass is read  from  the
	      indicated	 source.   If  the  password  is  correct  'Y user' is
	      printed and the program exit code	is 0.  If the password is  in-
	      correct  it prints 'N user' and the exit code is 1.  If there is
	      some other error the exit	 code  is  2.	This  feature  enables
	      x11vnc  to  be  a	 general  unix user password checking tool; it
	      could be used from scripts or other programs.  These %  password
	      checks also apply	to the -unixpw_nis and -unixpw_cmd options.

	      For  the % password check, if the	env. var. UNIXPW_CMD is	set to
	      a	command	then it	is run as the user (assuming the  password  is
	      correct.)	 The output of the command is not printed, the program
	      or script	must manage that by some other means.  The  exit  code
	      of  x11vnc  will	depend on the exit code	of the command that is

	      Use -nounixpw to disable unixpw mode if it was  enabled  earlier
	      in the cmd line (e.g. -svc mode)

       -unixpw_nis [list]

	      As  -unixpw  above,  however do not use su(1) but	rather use the
	      traditional getpwnam(3) +	crypt(3) method	to  verify  passwords.
	      All of the above -unixpw options and constraints apply.

	      This  mode  requires  that  the encrypted	passwords be readable.
	      Encrypted	passwords stored in /etc/shadow	will  be  inaccessible
	      unless x11vnc is run as root.

	      This is called "NIS" mode	simply because in most NIS setups user
	      encrypted	passwords are accessible (e.g. "ypcat passwd")	by  an
	      ordinary user and	so that	user can authenticate ANY user.

	      NIS is not required for this mode	to work	(only that getpwnam(3)
	      return the encrypted password is required), but it  is  unlikely
	      it  will work (as	an ordinary user) for most modern environments
	      unless NIS is available.	On the other hand, when	x11vnc is  run
	      as  root it will be able to to access /etc/shadow	even if	NIS is
	      not available (note running as root is often done	 when  running
	      x11vnc from inetd	and xdm/gdm/kdm).

	      Looked  at  another  way,	 if  you  do not want to use the su(1)
	      method provided by  -unixpw  (i.e.  su_verify()),	 you  can  run
	      x11vnc as	root and use -unixpw_nis.  Any users with passwords in
	      /etc/shadow can then be authenticated.

	      In -unixpw_nis mode, under no  circumstances  is	x11vnc's  user
	      password	verifying  function based on su	called (i.e. the func-
	      tion su_verify() that runs /bin/su in a pseudoterminal to	verify
	      passwords.)  However, if -unixpw_nis is used in conjunction with
	      the -find	and -create -display WAIT:... modes then, if x11vnc is
	      running  as  root,  /bin/su  may be called externally to run the
	      find or create commands.

       -unixpw_cmd cmd

	      As -unixpw above,	however	do not use su(1) but  rather  run  the
	      externally  supplied  command  cmd.  The first line of its stdin
	      will be the username and the second line the received  password.
	      If  the  command exits with status 0 (success) the VNC user will
	      be accepted.  It will be rejected	for any	other return status.

	      Dynamic passwords	and non-unix passwords,	e.g. LDAP, can be  im-
	      plemented	 this way by providing your own	custom helper program.
	      Note that	the remote viewer is given 3 tries to enter  the  cor-
	      rect  password,  and  so the program may be called in a row that
	      many (or more) times.

	      If a list	of allowed users is needed to limit who	 can  log  in,
	      use -unixpw [list] in addition to	this option.

	      In  FINDDISPLAY and FINDCREATEDISPLAY modes the cmd will also be
	      run with the RFB_UNIXPW_CMD_RUN env. var.	 non-empty and set  to
	      the  corresponding  display  find/create command.	 The first two
	      lines of input are the username and passwd as in the normal case
	      described	 above.	 To support FINDDISPLAY	and FINDCREATEDISPLAY,
	      cmd should run the requested  command  as	 the  user  (and  most
	      likely refusing to run it	if the password	is not correct.)  Here
	      is an example script (note it has	 a  hardwired  bogus  password

	      #!/bin/sh	# Example x11vnc -unixpw_cmd script.  #	Read the first
	      two lines	of stdin (user and passwd) read	user read pass

	      debug=0 if [ $debug = 1 ]; then echo  "user:  $user"  1>&2  echo
	      "pass: $pass" 1>&2 env | egrep -i	'rfb|vnc' 1>&2 fi

	      #	 Check	if the password	is valid.  # (A	real example would use
	      ldap lookup, etc!)  if [ "X$pass"	!= "Xabc" ]; then exit	1    #
	      incorrect	password fi

	      if  [  "X$RFB_UNIXPW_CMD_RUN"  = "X" ]; then exit	0    # correct
	      password else # Run the requested	 command  (finddisplay)	 if  [
	      $debug  =	1 ]; then echo "run: $RFB_UNIXPW_CMD_RUN" 1>&2 fi exec
	      /bin/su -	"$user"	-c "$RFB_UNIXPW_CMD_RUN" fi

	      In -unixpw_cmd mode, under no  circumstances  is	x11vnc's  user
	      password	verifying  function based on su	called (i.e. the func-
	      tion su_verify() that runs /bin/su in a pseudoterminal to	verify
	      passwords.)   It	is  up	to  the	supplied unixpw_cmd to do user
	      switching	if desired and if it has the permissions to do so.


	      Find the user's display using FINDDISPLAY. This is an alias  for
	      "-display	WAIT:cmd=FINDDISPLAY".

	      Note:  if	 a  -display  occurs later on the command line it will
	      override the -find setting.

	      For this and the next few	options	see -display  WAIT:...	 below
	      for all of the details.


	      Run  the	FINDDISPLAY  program,  print out the found display (if
	      any)   and   exit.    Output   is	  like:	  DISPLAY=:0.0	  DIS-
	      PLAY=:0.0,XPID=12345  or DISPLAY=:0.0,VT=7.  XPID	is the process
	      ID of the	found X	server.	 VT is the Linux virtual  terminal  of
	      the X server.


	      Have the FINDDISPLAY program list	all of your displays (i.e. all
	      the X displays on	the local machine that you have	access	rights
	      to).  x11vnc then	exits.

       -findauth [disp]

	      Apply the	-find/-finddpy heuristics to try to guess the XAUTHOR-
	      ITY file for DISPLAY 'disp'.  If 'disp' is  not  supplied,  then
	      the  value  in the -display on the cmdline is used; failing that
	      $DISPLAY is used;	and failing that ":0" is  used.	  x11vnc  then

	      If  nothing  is  printed out, that means no XAUTHORITY was found
	      for 'disp'; i.e. failure.	 If "XAUTHORITY=" is printed out, that
	      means  use  the  default (i.e. do	not set	XAUTHORITY).  If "XAU-
	      THORITY=/path/to/file" is	printed	out, then use that file.

	      XDM/GDM/KDM: if you are running x11vnc as	root and want to  find
	      the  XAUTHORITY  before anyone has logged	into an	X session yet,
	      use: x11vnc -env FD_XDM=1	-findauth ...  (This  will  also  find
	      the  XAUTHORITY if a user	is already logged into the X session.)
	      When running as root, FD_XDM=1 will  be  tried  if  the  initial
	      -findauth	fails.


	      First  try to find the user's display using FINDDISPLAY, if that
	      doesn't succeed create an	X session  via	the  FINDCREATEDISPLAY
	      method.	This is	an alias for "-display WAIT:cmd=FINDCREATEDIS-

	      Note: if a -display occurs later on the  command	line  it  will
	      override the -create setting.

	      SSH  NOTE: for both -find	and -create you	can (should!)  add the
	      "-localhost" option to force SSH tunnel access.


	      As in -create, except Xdummy instead of Xvfb.


	      As in -create, except Xvnc instead of Xvfb.


	      As in -create, except Xvnc.redirect instead of Xvfb.


	      Sets WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb

       -create_xsrv str

	      Sets WAIT:cmd=FINDCREATEDISPLAY-<str>  Can be on	cmdline	 after
	      anything that sets WAIT:.. and other things (e.g.	-svc, -xdmsvc)
	      to adjust	the X server list.   Example:  -svc  ...  -create_xsrv


	      Terminal	services mode based on SSL access.  Alias for -display
	      WAIT:cmd=FINDCREATEDISPLAY-Xvfb -unixpw -users unixpw= -ssl SAVE
	      Also "-service".

	      Note:  if	 a  -display, -unixpw, -users, or -ssl occurs later on
	      the command line it will override	the -svc setting.


	      As -svc except Xdummy instead of Xvfb.


	      As -svc except Xvnc instead of Xvfb.


	      As -svc with Xdummy,Xvfb.


	      Display manager Terminal services	mode based on SSL.  Alias  for
	      -display	WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp  -unixpw	-users
	      unixpw= -ssl SAVE	 Also "-xdm_service".

	      Note: if a -display, -unixpw, -users, or -ssl  occurs  later  on
	      the command line it will override	the -xdmsvc setting.

	      To  create  a  session  a	 user will have	to first log in	to the
	      -unixpw dialog and then log in again to the XDM/GDM/KDM  prompt.
	      Subsequent  re-connections  will	only require the -unixpw pass-
	      word.  See the discussion	under -display WAIT:...	for  more  de-
	      tails about XDM, etc configuration.

	      Remember	to  enable XDMCP in the	xdm-config, gdm.conf, or kdmrc
	      configuration file.  See -display	WAIT: for more info.


	      Display manager Terminal services	mode based on SSH.  Alias  for
	      -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp -localhost.

	      The  -localhost  option  constrains connections to come in via a
	      SSH tunnel (which	will require a login).	To create a session  a
	      user  will  also have to log into	the XDM	GDM KDM	prompt.	Subse-
	      quent re-connections will	only only require the SSH login.   See
	      the  discussion  under  -display WAIT:...	for more details about
	      XDM, etc configuration.

	      Remember to enable XDMCP in the xdm-config, gdm.conf,  or	 kdmrc
	      configuration file.  See -display	WAIT: for more info.


	      Present a	"Press 'Escape'	for System Greeter" option to the con-
	      necting VNC client in combined -unixpw and xdmcp	FINDCREATEDIS-
	      PLAY modes (e.g. -xdmsvc).

	      Normally	in  a  -unixpw mode the	VNC client must	supply a valid
	      username and password to gain access.  However, if  -unixpw_sys-
	      tem_greeter   is	supplied  AND  the  FINDCREATEDISPLAY  command
	      matches 'xdmcp', then the	user has the option  to	 press	Escape
	      and  then	 get  a	 XDM/GDM/KDM login/greeter panel instead. They
	      will then	 supply	 a  username  and  password  directly  to  the

	      Otherwise,  in xdmcp FINDCREATEDISPLAY mode the user must	supply
	      his username and password	TWICE.	First to  the  initial	unixpw
	      login  dialog, and second	to the subsequent XDM/GDM/KDM greeter.
	      Note that	if the user re-connects	and supplies his username  and
	      password	in  the	unixpw dialog the xdmcp	greeter	is skipped and
	      he is connected directly to his  existing	 X  session.   So  the
	      -unixpw_system_greeter  option  avoids  the  extra password at X
	      session creation time.

	      Example:	x11vnc -xdmsvc -unixpw_system_greeter See -unixpw  and
	      -display WAIT:...	for more info.

	      The  special  options  after  a colon at the end of the username
	      (e.g. user:solid)	described under	-display WAIT:	are  also  ap-
	      plied in this mode if they are typed in before the user hits Es-
	      cape.  The username is ignored but the colon options are not.

	      The default message is 2 lines in	a small	 font,	set  the  env.
	      var.  X11VNC_SYSTEM_GREETER1=true	 for  a	 1  line  message in a
	      larger font.

	      If the user pressed Escape the FINDCREATEDISPLAY command will be
	      run with the env.	var. X11VNC_XDM_ONLY=1.

	      Remember	to  enable XDMCP in the	xdm-config, gdm.conf, or kdmrc
	      configuration file.  See -display	WAIT: for more info.

       -redirect port

	      As in FINDCREATEDISPLAY-Xvnc.redirect mode except	redirect imme-
	      diately  (i.e.  without  X session finding or creation) to a VNC
	      server listening on port.	You can	also supply host:port to redi-
	      rect to a	different machine.

	      If  0  <=	port < 200 it is taken as a VNC	display	(5900 is added
	      to get the actual	port), if port < 0 then	-port is used.

	      Probably the only	reason to use the -redirect option is in  con-
	      junction	with  SSL  support,  e.g. -ssl SAVE.  This provides an
	      easy way to add SSL encryption to	a VNC  server  that  does  not
	      support SSL (e.g.	Xvnc or	In fact, the protocol does not
	      even need	to be VNC, and so "-rfbport port1 -ssl SAVE  -redirect
	      host:port2" can act as a replacement for stunnel(1).

	      This  mode  only allows one redirected connection.  The -forever
	      option does not apply.  Use -inetd or -loop for persistent  ser-

       -display	WAIT:...

	      A	 special  usage	 mode  for the normal -display option.	Useful
	      with -unixpw, but	can be used independently of it.  If the  dis-
	      play  string  begins  with  WAIT:	 then x11vnc waits until a VNC
	      client connects before opening the X display (or -rawfb device).

	      This could be useful for delaying	opening	the display  for  cer-
	      tain usage modes (say if x11vnc is started at boot time and no X
	      server is	running	or users logged	in yet).

	      If the string is,	e.g. WAIT:0.0 or WAIT:1, i.e. "WAIT" in	 front
	      of a normal X display, then that indicated display is used.

	      One   can	  also	 insert	  a   geometry	between	 colons,  e.g.
	      WAIT:1280x1024:... to set	the size of the	display	the VNC	client
	      first  attaches to since some VNC	viewers	will not automatically
	      adjust to	a new framebuffer size.

	      A	more interesting case is like this:


	      in which case the	command	after "cmd="  is  run  to  dynamically
	      work  out	 the  DISPLAY and optionally the XAUTHORITY data.  The
	      first line of the	command	 output	 must  be  of  the  form  DIS-
	      PLAY=<xdisplay>.	 On Linux if the virtual terminal is known ap-
	      pend ",VT=n" to this string and the chvt(1) program will also be
	      run.   Any remaining output is taken as XAUTHORITY data.	It can
	      be either	of the form XAUTHORITY=<file> or raw  xauthority  data
	      for the display. For example;

	      xauth extract - $DISPLAY"

	      NOTE:  As	 specified  in	the previous paragraph,	you can	supply
	      your own WAIT:cmd=... program or script, BUT there are two  very
	      useful  *BUILT-IN*  ones:	 FINDDISPLAY  (alias  -find above) and
	      FINDCREATEDISPLAY	(alias -create above.)	Most people use	 these
	      instead of creating their	own script.  Read the following	(espe-
	      cially the BUILT-IN modes	sections)  to  see  how	 to  configure
	      these two	useful builtin -display	WAIT: modes.

	      In  the  case of -unixpw (and -unixpw_nis	only if	x11vnc is run-
	      ning as root), then the cmd= command is run as the user who just
	      authenticated via	the login and password prompt.

	      In the case of -unixpw_cmd, the commands will also be run	as the
	      logged-in	user, as long as the user-supplied helper program sup-
	      ports RFB_UNIXPW_CMD_RUN (see the	-unixpw_cmd option.)

	      Also  in	the  case  of -unixpw, the user	logging	in can place a
	      colon at the end of her  username	 and  supply  a	 few  options:
	      scale=,  scale_cursor=  (or sc=),	solid (or so), id=, clear_mods
	      (or cm), clear_keys (or ck), clear_all (or ca), repeat,  speeds=
	      (or  sp=),  readtimeout=	(or rd=), viewonly (or vo), nodisplay=
	      (or nd=),	rotate=	(or ro=), or noncache (or nc),	all  separated
	      by  commas  if  there  is	more than one.	After the user logs in
	      successfully, these options will be applied to the  VNC  screen.
	      For example,

	      login: fred:scale=3/4,sc=1,repeat	Password: ...

	      login: runge:sp=modem,rd=120,solid

	      for  convenience	m/n  implies scale= e.g. fred:3/4  If you type
	      and enter	your password incorrectly, to retrieve your long  "lo-
	      gin:"  line  press  the  Up  arrow  once (before typing anything

	      Most of these colon options only apply to	the  builtin  FINDDIS-
	      PLAY  and	FINDCREATEDISPLAY modes, but note that they are	passed
	      to the extrenal command in the environment as well and so	 could
	      be used.

	      In  the login panel, press F1 to get a list of the available op-
	      tions that you can add after the username.

	      Another option is	"geom=WxH" or "geom=WxHxD" (or ge=). This only
	      has  an effect in	FINDCREATEDISPLAY mode when a virtual X	server
	      such as Xvfb is going to be created.   It	 sets  the  width  and
	      height  of  the  new  display, and optionally the	color depth as

	      You can  also  supply  "gnome",  "kde",  "twm",  "fvwm",	"mwm",
	      "dtwm",  "wmaker",  "xfce", "lxde", "enlightenment", "Xsession",
	      or "failsafe" (same as "xterm") to have the created display  use
	      that mode	for the	user session.

	      Specify  "tag=..."  to set the unique FD_TAG desktop session tag
	      described	below.	Note: this  option  will  be  ignored  if  the
	      FD_TAG  env.  var. is already set	or if the viewer-side supplied
	      value is not completely composed of alphanumeric or '_'  or  '-'

	      User  preferences	 file:	Instead	 of  having  the  user type in
	      geom=WxH,... etc.	every time he logs in to find or create	his  X
	      session,	if you set FD_USERPREFS	to a string that does not con-
	      tain the "/"  character,	then  the  user's  home	 directory  is
	      prepended	 to  that string and if	the file exists	its first line
	      is read and appended to any options he supplied  at  the	login:
	      prompt.	For  example  -env FD_USERPREFS=.x11vnc_create and the
	      user put "geom=1600x1200"	in his ~/.x11vnc_create	file.

	      To disable the  option  setting  set  the	 environment  variable
	      X11VNC_NO_UNIXPW_OPTS=1  before  starting	 x11vnc.   To  set any
	      other options, the user can use the gui (x11vnc -gui connect) or
	      the  remote  control  method  (x11vnc -R opt:val)	during his VNC

	      So we see	the combination	of -display WAIT:cmd=...  and  -unixpw
	      allows  automatic	pairing	of an unix authenticated VNC user with
	      his desktop.  This could be very useful on SunRays and also  any
	      system  where  multiple  users  share a given machine.  The user
	      does not need to remember	special	ports or passwords set up  for
	      his desktop and VNC.

	      A	 nice way to use WAIT:cmd=... is out of	inetd(8) (it automati-
	      cally forks a new	x11vnc for  each  user).   You	can  have  the
	      x11vnc  inetd spawned process run	as, say, root or nobody.  When
	      run as root (for either inetd or display manager), you can  also
	      supply  the  option  "-users unixpw=" to have the	x11vnc process
	      switch to	the user as well.  Note:  there	 will  be  a  2nd  SSL
	      helper process that will not switch, but it is only encoding and
	      decoding the encrypted stream at that point.

	      BUILT-IN modes:

	      -- Automatic Finding of User X Sessions --

	      As a special case, WAIT:cmd=FINDDISPLAY will run a  script  that
	      works  on	most Unixes to determine a user's DISPLAY variable and
	      xauthority data (see who(1) ).

	      NOTE: The	option "-find" is an alias for this mode.

	      To have this default script printed to  stdout  (e.g.  for  cus-
	      tomization)  run	with  WAIT:cmd=FINDDISPLAY-print  To  have the
	      script run to print what display it would	find use "-finddpy" or

	      The  standard script runs	xdpyinfo(1) run	on potential displays.
	      If your X	server(s) have a login greeter that exclusively	 grabs
	      the Xserver, then	xdpyinfo blocks	forever	and this mode will not
	      work.  See
	      for  how to disable this for dtgreet on Solaris and possibly for
	      other greeters.

	      In -find/cmd=FINDDISPLAY mode, if	you set	FD_XDM=1, e.g. 'x11vnc
	      -env FD_XDM=1 -find ...' and x11vnc is running as	root (e.g. in-
	      etd) then	it will	try to find the	XAUTHORITY file	of  a  running
	      XDM/GDM/KDM  login  greeter  (i.e.  no user has logged into an X
	      session yet.)

	      As another special case, WAIT:cmd=HTTPONCE will allow x11vnc  to
	      service one http request and then	exit.  This is usually done in
	      -inetd mode to run  on,  say,  port  5800	 and  allow  the  Java
	      vncviewer	to be downloaded by client web browsers.  For example:

	      5815  stream tcp nowait root /usr/sbin/tcpd /.../x11vnc \	-inetd
	      -q -http_ssl -prog /.../x11vnc \ -display	WAIT:cmd=HTTPONCE

	      Where /.../x11vnc	is the full path to x11vnc.  It	is used	in the
	      Apache SSL-portal	example	(see FAQ).

	      In  this	mode  you can set X11VNC_SKIP_DISPLAY to a comma sepa-
	      rated list of displays (e.g. ":0,:1") to ignore in  the  finding
	      process.	The ":"	is optional.  Ranges n-m e.g. 0-20 can also be
	      supplied.	This string can	also be	set by the connecting user via
	      "nd="  using  "+"	 instead  of  ","   If	"nd=all"  or  you  set
	      X11VNC_SKIP_DISPLAY=all then all display finding fails as	if you
	      set X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (below.)

	      On  some	systems	 lsof(1)  can be very slow.  Set the env. var.
	      FIND_DISPLAY_NO_LSOF=1 to	skip using lsof	to  try	 to  find  the
	      Linux   VT   the	 X   server  is	 running  on.	set  FIND_DIS-
	      PLAY_NO_VT_FIND=1	to avoid looking at all.

	      -- Automatic Creation of User X Sessions --

	      An interesting option is WAIT:cmd=FINDCREATEDISPLAY that is like
	      FINDDISPLAY  in that is uses the same method to find an existing
	      display.	However, if it does  not  find	one  it	 will  try  to
	      *start*  up  an X	server session for the user.  This is the only
	      time x11vnc tries	to actually start up an	X server.

	      NOTE: The	option "-create" is an alias for this mode.

	      It will start looking for	an open	display	number at :20 Override
	      via X11VNC_CREATE_STARTING_DISPLAY_NUMBER=n By default 80	X dis-
	      plays are	allowed	(i.e. going to :99) Override  via  X11VNC_CRE-

	      For  its	heuristics, the	create display script sets LC_ALL=C so
	      that command output is uniform.  By default it will try  to  re-
	      store  LC_ALL  right before starting the user session.  However,
	      if you don't  mind  it  keeping  LC_ALL=C	 set  the  env.	 var.:

	      By default FINDCREATEDISPLAY will	try Xvfb and then Xdummy:

	      The   Xdummy   wrapper   is  part	 of  the  x11vnc  source  code
	      (x11vnc/misc/Xdummy)  It should be available in  PATH  and  have
	      run "Xdummy -install" once to create the shared library.	Xdummy
	      only works on Linux.  As of 12/2009 it no	longer needs to	be run
	      as root, and the default is to not run as	root.  In some circum-
	      stances permissions may require running it  as  root,  in	 these
	      cases  specify FD_XDUMMY_RUN_AS_ROOT=1, this is the same as sup-
	      plying -root to the Xdummy cmdline.

	      Xvfb is available	on most	platforms and does not require root.

	      An advantage of Xdummy over Xvfb is that Xdummy  supports	 RANDR
	      dynamic screen resizing.

	      When  x11vnc  exits (i.e.	user disconnects) the X	server session
	      stays running in the background.	The FINDDISPLAY	will  find  it
	      directly	next  time.   The  user	must exit the X	session	in the
	      usual way	for it to terminate (or	kill the X server  process  if
	      all else fails).

	      To troubleshoot the FINDCREATEDISPLAY mechanism, set the follow-
	      ing env. var. to	an  output  log	 file,	e.g  -env  CREATE_DIS-

	      So  this is a somewhat odd mode for x11vnc in that it will start
	      up and poll virtual X servers!  This can be used from, say,  in-
	      etd(8)  to  provide a means of definitely	getting	a desktop (ei-
	      ther real	or virtual) on the machine.  E.g. a desktop service:

	      5900 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc -inetd -q
	      -http  -ssl  SAVE	 -unixpw  -users unixpw=\ -passwd secret -prog
	      /.../x11vnc \ -display WAIT:cmd=FINDCREATEDISPLAY

	      Where /.../x11vnc	is the full path to x11vnc.

	      See the -svc/-service option alias above.

	      If for some reason you do	not want x11vnc	to ever	try to find an
	      existing	 display   set	the  env.  var	X11VNC_FINDDISPLAY_AL-
	      WAYS_FAILS=1 (also -env  ...)   This  is	the  same  as  setting
	      X11VNC_SKIP_DISPLAY=all or supplying "nd=all" after "username:"

	      Use  WAIT:cmd=FINDCREATEDISPLAY-print  to	 print	out the	script
	      that is used for this.

	      You  can	specify	 the  preferred	 X  server  order  via	 e.g.,
	      WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb,X	 and/or	leave out ones
	      you do not want.	The the	case "X" means try to start up a real,
	      hardware	X server using xinit(1)	or startx(1).  If there	is al-
	      ready an X server	running	the X case may only work on Linux (see
	      startx(1)	).

	      "Xvnc"  will  start  up a	VNC X server (real- or tight-vnc, e.g.
	      use if Xvfb is not available).  "Xsrv" will start	up the	server
	      program  in  the	variable "FD_XSRV" if it is non-empty. You can
	      make this	be a wrapper script if you like	(it  must  handle  :N,
	      -geometry, and -depth and	other X	server options).

	      You  can	set  the  environment variable FD_GEOM (or X11VNC_CRE-
	      ATE_GEOM)	to WxH or WxHxD	to set the width and  height  and  op-
	      tionally	the  color depth of the	created	display.  You can also
	      set FD_SESS to be	the session (short name	of the	windowmanager:
	      kde, gnome, twm, failsafe, etc.).	FD_OPTS	contains extra options
	      to pass to the X server. You can also set	FD_PROG	to be the full
	      path to the session/windowmanager	program.

	      More  FD tricks:	FD_CUPS=port or	FD_CUPS=host:port will set the
	      cups  printing  environment.   Similarly	for   FD_ESD=port   or
	      FD_ESD=host:port	for esddsp sound redirection.  Set FD_EXTRA to
	      a	command	to be run a few	seconds	after the X server starts  up.
	      Set  FD_TAG to be	a unique name for the session, it is set as an
	      X	property, that makes FINDDISPLAY only find sessions with  that
	      tag value.

	      Set  FD_XDMCP_IF	to the network interface that the display man-
	      ager is running on; default is 'localhost' but you may  need  to
	      set  it to '::1' on some IPv6 only systems or misconfigured dis-
	      play managers.

	      If you want the FINDCREATEDISPLAY	session	to  contact  an	 XDMCP
	      login  manager  (xdm/gdm/kdm)  on	 the  same  machine,  then use
	      "Xvfb.xdmcp" instead of "Xvfb", etc.  The	user will have to sup-
	      ply  his username	and password one more time (but	he gets	to se-
	      lect his desktop type so that can	be useful).  For this to work,
	      you  will	 need to enable	localhost XDMCP	(udp port 177) for the
	      display manager.	This seems to be:

	      for gdm in gdm.conf:   Enable=true in section [xdmcp] for	kdm in
	      kdmrc:	   Enable=true	in section [Xdmcp] for xdm in xdm-con-
	      fig: DisplayManager.requestPort: 177

	      See  the	shorthand  options   above   "-svc",   "-xdmsvc"   and
	      "-sshxdmsvc"  that  specify  the	above  options for some	useful

	      If you set the env. var WAITBG=1 x11vnc will go into  the	 back-
	      ground once listening in wait mode.

	      Another  special	mode  is  FINDCREATEDISPLAY-Xvnc.redirect, (or
	      FINDDISPLAY-Xvnc.redirect).  In this case	it will	start up  Xvnc
	      as above if needed, but instead of polling it in its normal way,
	      it simply	does a socket redirection of the connected VNC	viewer
	      to the Xvnc.

	      So  in Xvnc.redirect x11vnc does no VNC but merely transfers the
	      data back	and  forth.   This  should  be	faster	then  x11vnc's
	      polling  method,	but  not as fast as connecting directly	to the
	      Xvnc with	the VNC	Viewer.	 The idea here is to take advantage of
	      x11vnc's display finding/creating	scheme,	SSL, and perhaps a few
	      others.  Most of x11vnc's	options	do not apply in	this mode.

	      Xvnc.redirect should also	work for the  X	server	module
	      for  the	h/w  display however it	will work only for finding the
	      display and the user must	already	be logged into the X console.

       -vencrypt mode

	      The VeNCrypt extension to	 the  VNC  protocol  allows  encrypted
	      SSL/TLS connections.  If the -ssl	mode is	enabled, then VeNCrypt
	      is enabled as well BY DEFAULT (they both use a  SSL/TLS  tunnel,
	      only the protocol	handshake is a little different.)

	      To  control  when	 and  how  VeNCrypt  is	used, specify the mode
	      string.  If mode is "never", then	VeNCrypt is not	used.  If mode
	      is  "support" (the default) then VeNCrypt	is supported.  If mode
	      is "only", then the similar and older ANONTLS  protocol  is  not
	      simultaneously  supported.   x11vnc's  normal SSL	mode (vncs://)
	      will be supported	under -ssl unless you set mode to "force".

	      If mode is prefixed with "nodh:",	then Diffie Hellman  anonymous
	      key  exchange  is	disabled.  If mode is prefixed with "nox509:",
	      then X509	key exchange is	disabled.

	      To disable all Anonymous Diffie-Hellman access  (susceptible  to
	      Man-In-The-Middle	 attack)  you  will  need to supply "-vencrypt
	      nodh:support -anontls never" or "-vencrypt nodh:only"

	      If mode is prefixed with "newdh:", then new Diffie  Hellman  pa-
	      rameters	are  generated	for  each connection (this can be time
	      consuming: 1-60 secs; see	-dhparams  below  for  a  faster  way)
	      rather than using	the fixed values in the	program.  Using	fixed,
	      publicly known values is not known to  be	 a  security  problem.
	      This setting applies to ANONTLS as well.

	      Long example: -vencrypt newdh:nox509:support

	      Also, if mode is prefixed	with "plain:", then if -unixpw mode is
	      active the VeNCrypt "*Plain" username+passwd method  is  enabled
	      for  Unix	 logins.   Otherwise  in -unixpw mode the normal login
	      panel is provided.

	      You *MUST* supply	the -ssl option	for  VeNCrypt  to  be  active.
	      The -vencrypt option only	fine-tunes its operation.

       -anontls	mode

	      The  ANONTLS  extension  to  the	VNC  protocol allows encrypted
	      SSL/TLS connections.  If the -ssl	mode is	enabled, then  ANONTLS
	      is  enabled  as well BY DEFAULT (they both use a SSL/TLS tunnel,
	      only the protocol	handshake is a little different.)

	      ANONTLS is an older SSL/TLS mode introduced by vino.

	      It is referred to	as 'TLS' for its registered VNC	 security-type
	      name,  but we use	the more descriptive 'ANONTLS' here because it
	      provides only Anonymous  Diffie-Hellman  encrypted  connections,
	      and hence	no possibility for certificate authentication.

	      To  control  when	 and  how  ANONTLS  is	used, specify the mode
	      string.  If mode is "never", then	ANONTLS	is not used.  If  mode
	      is  "support"  (the default) then	ANONTLS	is supported.  If mode
	      is "only", then the similar VeNCrypt protocol is not  simultane-
	      ously  supported.	  x11vnc's  normal  SSL	mode (vncs://) will be
	      supported	under -ssl unless you set mode to "force".

	      If mode is prefixed with "newdh:", then new Diffie  Hellman  pa-
	      rameters	are  generated	for  each connection (this can be time
	      consuming: 1-60 secs; see	-dhparams  below  for  a  faster  way)
	      rather than using	the fixed values in the	program.  Using	fixed,
	      publicly known values is not known to  be	 a  security  problem.
	      This  setting  applies to	VeNCrypt as well.  See the description
	      of "plain:" under	-vencrypt.

	      Long example: -anontls newdh:plain:support

	      You *MUST* supply	the -ssl option	for ANONTLS to be active.  The
	      -anontls option only fine-tunes its operation.


	      Same  as:	"-vencrypt never -anontls never"  i.e. it disables the
	      VeNCrypt and ANONTLS encryption methods and only allows standard
	      SSL  tunneling.	You  must also supply the -ssl ... option (see

       -dhparams file

	      For some operations a set	of Diffie  Hellman  parameters	(prime
	      and generator) is	needed.	 If so,	use the	parameters in file. In
	      particular, the VeNCrypt and  ANONTLS  anonymous	DH  mode  need
	      them.   By default a fixed set is	used. If you do	not want to do
	      that you can specify "newdh:" to the -vencrypt and -anontls  op-
	      tions  to	 generate a new	set each session.  If that is too slow
	      for you, use -dhparams file to a set you	created	 manually  via
	      "openssl dhparam -out file 1024"


	      Disable  the  -ssl  option (see below). Since -ssl is off	by de-
	      fault -nossl would only be used on the commandline to unset  any
	      *earlier*	-ssl option (or	-svc...)

       -ssl [pem]

	      Use  the openssl library ( to provide a built-in
	      encrypted	SSL/TLS	tunnel between VNC viewers and	x11vnc.	  This
	      requires	libssl	support	 to  be	 compiled into x11vnc at build
	      time.  If	x11vnc is not built with libssl	support	it  will  exit
	      immediately  when	 -ssl  is prescribed.  See the -stunnel	option
	      below for	an alternative.

	      The VNC Viewer-side needs	to support SSL/TLS as well.  See  this
	      URL and also the discussion below	for ideas on how to enable SSL
	      support	    for	      the	viewer:	      http://www.karl- nel-viewers	.  x11vnc pro-
	      vides an SSL enabled Java	viewer applet in the  classes/ssl  di-
	      rectory  (-http  or -httpdir options.)  The SSVNC	viewer package
	      supports SSL tunnels too.

	      If the VNC Viewer	supports VeNCrypt or ANONTLS  (vino's  encryp-
	      tion  mode)  they	 are  also supported by	the -ssl mode (see the
	      -vencrypt	and -anontls options for more info;  use  -sslonly  to
	      disable both of them.)

	      Use  "-ssl  /path/to/mycert.pem"	to  specify an SSL certificate
	      file in PEM format to use	to identify and	provide	a key for this
	      server.	See  openssl(1)	 for  more  info  about	 PEMs  and the
	      -sslGenCert and "-ssl SAVE" options  below  for  how  to	create

	      The connecting VNC viewer	SSL tunnel can (at its option) authen-
	      ticate this server if it has the public key part of the certifi-
	      cate (or a common	certificate authority, CA, is a	more sophisti-
	      cated way	to verify this server's	cert,  see  -sslGenCA  below).
	      This  authentication  is	done  to prevent Man-In-The-Middle at-
	      tacks.   Otherwise,  if  the  VNC	 viewer	 simply	 accepts  this
	      server's key WITHOUT verification, the traffic is	protected from
	      passive sniffing on the network, but *NOT* from  Man-In-The-Mid-
	      dle attacks. There are hacker tools like dsniff/webmitm and cain
	      that implement SSL Man-In-The-Middle attacks.

	      If [pem] is empty	or the string "SAVE" then the openssl(1)  com-
	      mand  must  be  available	 to generate the certificate the first
	      time.  A self-signed certificate is generated (see -sslGenCA and
	      -sslGenCert  for	use  of	 a Certificate Authority.)  It will be
	      saved to the file	~/.vnc/certs/server.pem.  On subsequent	 calls
	      if that file already exists it will be used directly.

	      Use  "SAVE_NOPROMPT" to avoid being prompted to protect the gen-
	      erated key with a	passphrase.  However in	-inetd and  -bg	 modes
	      there will be no prompting for a passphrase in either case.

	      If  [pem]	 is  "SAVE_PROMPT"  the	server.pem certificate will be
	      created based on your answers to its prompts for all  info  such
	      as OrganizationalName, CommonName, etc.

	      Use  "SAVE-<string>"  and	"SAVE_PROMPT-<string>" to refer	to the
	      file ~/.vnc/certs/server-<string>.pem instead (it	will be	gener-
	      ated  if	it  does not already exist).  E.g. "SAVE-charlie" will
	      store to the file	~/.vnc/certs/server-charlie.pem

	      Examples:	x11vnc -ssl SAVE -display :0 ...   x11vnc  -ssl	 SAVE-
	      someother	-display :0 ...

	      If  [pem]	 is "TMP" and the openssl(1) utility command exists in
	      PATH, then a temporary, self-signed certificate will  be	gener-
	      ated for this session.  If openssl(1) cannot be used to generate
	      a	temporary certificate x11vnc exits immediately.	 The temporary
	      cert will	be discarded when x11vnc exits.

	      If  successful  in using openssl(1) to generate a	temporary cer-
	      tificate in "SAVE" or "TMP" creation modes, the public  part  of
	      it  will	be  displayed to stderr	(e.g. one could	copy it	to the
	      client-side to provide authentication of the server to VNC view-

	      NOTE:  In	 "TMP" mode, unless you	safely copy the	public part of
	      the temporary Cert to the	viewer for authenticate	 *every	 time*
	      (unlikely...),  then only	passive	sniffing attacks are prevented
	      and you are still	open to	Man-In-The-Middle  attacks.   This  is
	      why the default "SAVE" mode is preferred (and more sophisticated
	      CA mode too).  Only with saved keys AND the VNC viewer authenti-
	      cating  them (via	the public certificate), are Man-In-The-Middle
	      attacks prevented.

	      If [pem] is "ANON" then the  Diffie-Hellman  anonymous  key  ex-
	      change method is used.  In this mode there are *no* SSL certifi-
	      cates and	so it is not possible to authenticate either  the  VNC
	      server  or  VNC  client.	Thus only passive network sniffing at-
	      tacks are	avoided: the "ANON" method is susceptible  to  Man-In-
	      The-Middle  attacks.   "ANON"  is	not recommended; instead use a
	      SSL PEM you created or the default "SAVE"	method.

	      See -ssldir  below  to  use  a  directory	 besides  the  default

	      If your x11vnc binary was	not compiled with OpenSSL library sup-
	      port, use	of the -ssl option will	induce	an  immediate  failure
	      and exit.	 For such binaries, consider using the -stunnel	option
	      for SSL encrypted	connections.

	      Misc Info: In temporary cert creation mode "TMP",	set  the  env.
	      var.  X11VNC_SHOW_TMP_PEM=1  to have x11vnc print	out the	entire
	      certificate, including the PRIVATE KEY part, to  stderr.	 There
	      are  better  ways	 to  get/save this info.  See "SAVE" above and
	      "-sslGenCert" below.

       -ssltimeout n

	      Set SSL read timeout to n	seconds.  In some situations (i.e.  an
	      iconified	 viewer	 in  Windows) the viewer stops talking and the
	      connection is dropped after the default timeout (25s  for	 about
	      the  first  minute, 43200s later).  Set to zero to poll forever.
	      Set to a negative	value to use the builtin setting.

	      Note that	this value does	NOT apply to the  *initial*  ssl  init
	      connection.   The	 default  timeout for that is 20sec.  Use -env
	      SSL_INIT_TIMEOUT=n to modify it.


	      Exit at the first	SSL connection failure.	Useful when  scripting
	      SSL  connections (e.g. x11vnc is started via ssh)	and you	do not
	      want x11vnc waiting around for more connections, tying up	ports,

       -ssldir dir

	      Use  dir	as  an	alternate  ssl	certificate and	key management
	      toplevel directory.  The default is ~/.vnc/certs

	      This directory is	used to	store server  and  other  certificates
	      and  keys	 and also other	materials.  E.g. in the	simplest case,
	      "-ssl SAVE" will store the x11vnc	server cert in dir/server.pem

	      Use of alternate directories via -ssldir allows  you  to	manage
	      multiple VNC Certificate Authority (CA) keys.  Another use is if
	      ~/.vnc/cert is on	an NFS share you might want your  certificates
	      and keys to be on	a local	filesystem to prevent network snooping
	      (for example -ssldir /var/lib/x11vnc-certs).

	      -ssldir affects nearly all of the	other -ssl* options, e.g. -ssl
	      SAVE, -sslGenCert, etc..

       -sslverify path

	      For  either  of  the -ssl	or -stunnel modes, use path to provide
	      certificates to authenticate incoming VNC	 *Client*  connections
	      (normally	only the server	is authenticated in SSL.)  This	can be
	      used as a	method to replace standard password authentication  of

	      If  path	is a directory it contains the client (or CA) certifi-
	      cates in separate	files.	If path	is a file, it contains one  or
	      more  certificates.  See special tokens below.  These correspond
	      to the "CApath = dir" and	"CAfile	= file"	stunnel	options.   See
	      the stunnel(8) manpage for details.

	      Examples:	x11vnc -ssl -sslverify ~/my.crt	x11vnc -ssl -sslverify

	      Note that	if path	is a directory,	it must	contain	the  certs  in
	      separate files named like	<HASH>.0, where	the value of <HASH> is
	      found by running the command  "openssl  x509  -hash  -noout  -in
	      file.crt".  Evidently  one  uses	<HASH>.1  if there is a	colli-

	      The  the	key-management	utility	 "-sslCertInfo	 HASHON"   and
	      "-sslCertInfo  HASHOFF"  will create/delete these	hashes for you
	      automatically (via symlink) in  the  HASH	 subdirs  it  manages.
	      Then you can point -sslverify to the HASH	subdir.

	      Special  tokens: in -ssl mode, if	path is	not a file or a	direc-
	      tory, it is taken	as a comma separated list of tokens  that  are
	      interpreted as follows:

	      If  a  token is "CA" that	means load the CA/cacert.pem file from
	      the ssl directory.  If a token is	"clients" then all  the	 files
	      clients/*.crt  in	 the  ssl directory are	loaded.	 Otherwise the
	      file clients/token.crt is	attempted to be	loaded.	 As a  kludge,
	      use a token like ../server-foo to	load a server cert if you find
	      that necessary.

	      Use -ssldir to use a directory different from  the  ~/.vnc/certs

	      Note that	if the "CA" cert is loaded you do not need to load any
	      of the certs that	have been signed by it.	 You will need to load
	      any additional self-signed certs however.

	      Examples:	 x11vnc	 -ssl  -sslverify  CA  x11vnc  -ssl -sslverify
	      self:fred,self:jim x11vnc	-ssl -sslverify	CA,clients

	      Usually  "-sslverify  CA"	 is  the  most	effective.   See   the
	      -sslGenCA	 and  -sslGenCert  options below for how to set	up and
	      manage the CA framework.

	      NOTE: the	 following  utilities,	-sslGenCA,  -sslGenCert,  -ss-
	      lEncKey,	-sslCertInfo,  and  -sslCRL are	provided for complete-
	      ness, but	for casual usage they are overkill.

	      They provide VNC Certificate Authority  (CA)  key	 creation  and
	      server  /	 client	key generation and signing.  So	they provide a
	      basic Public Key management framework for	VNC-ing	 with  x11vnc.
	      (note that they require openssl(1) be installed on the system)

	      However, the simplest usage mode,	"-ssl TMP" (where x11vnc auto-
	      matically	generates its own, self-signed,	temporary key and  the
	      VNC  viewers  always accept it, e.g. accepting via a dialog box)
	      is probably safe enough for most scenarios.   CA	management  is
	      not needed.

	      To  protect against Man-In-The-Middle attacks the	"TMP" mode can
	      be improved by using "-ssl SAVE" (same as	"-ssl",	i.e.  the  de-
	      fault)  to have x11vnc create a longer term self-signed certifi-
	      cate, and	then (safely) copy the corresponding public  key  cert
	      to  the  desired client machines (care must be taken the private
	      key part is not stolen; you will be prompted for a passphrase).

	      So keep in mind no CA key	creation or management (-sslGenCA  and
	      -sslGenCert)  is needed for either of the	above two common usage

	      One might	want to	use -sslGenCA and -sslGenCert  if  you	had  a
	      large  number  of	 VNC client and	server workstations.  That way
	      the administrator	could generate a single	CA key with  -sslGenCA
	      and distribute its certificate part to all of the	workstations.

	      Next, he could create signed VNC server keys (-sslGenCert	server
	      ...) for each workstation	or user	that then x11vnc would use  to
	      authenticate itself to any VNC client that has the CA cert.

	      Optionally,  the	admin  could  also  make it so the VNC clients
	      themselves are authenticated to x11vnc (-sslGenCert client  ...)
	      For  this	 -sslverify  would  be	pointed	to the CA cert (and/or
	      self-signed certs).

	      x11vnc will be able to use all of	these cert and key files.   On
	      the  VNC	client	side, they will	need to	be "imported" somehow.
	      Web browsers have	"Manage	Certificates" actions as does the Java
	      applet  plugin  Control Panel.  stunnel can also use these files
	      (see the ss_vncviewer example script in the FAQ and SSVNC.)

       -sslCRL path

	      Set the Certificate Revocation Lists (CRL) to path.   This  set-
	      ting applies for both -ssl and -stunnel modes.

	      If  path	is  a  file, the file contains one or more CRLs	in PEM
	      format.  If path is a directory, it contains hash	named files of
	      CRLs  in	the  usual  OpenSSL manner.  See the OpenSSL and stun-
	      nel(8) documentation for more info.

	      This option only applies if -sslverify  has  been	 supplied:  it
	      checks for revocation along the certificate chain	used to	verify
	      the VNC client.  The -sslCRL setting will	be ignored  when  -ss-
	      lverify is not specified.

	      Note that	if a CRL's expiration date has passed, all SSL connec-
	      tions will fail regardless of if they are	related	to the subject
	      of the CRL or not.

	      Only  rarely  will  one's	x11vnc -ssl infrastructure be so large
	      that this	option would be	useful (since normally maintaining the
	      contents	of the -sslverify file or directory should be enough.)
	      However, when using x11vnc with  a  Certificate  Authority  (see
	      -sslGenCA)  to authenticate Clients via SSL/TLS, the -sslCRL op-
	      tion can be useful to revoke users' certs	whose private SSL keys
	      were  lost  or stolen (e.g. laptop.)  This way a new CA cert+key
	      does not need to be created and new signed client	keys generated
	      and distributed to all users.

	      To  create  a  CRL  file	with revoked certificates the commands
	      'openssl ca -revoke ...' and 'openssl ca -gencrl ...'  are  use-
	      ful.  (Run them in ~/.vnc/certs)

       -sslGenCA [dir]

	      Generate	your  own  Certificate Authority private key, certifi-
	      cate, and	other files in directory [dir].	 x11vnc	then exits.

	      If [dir] is not supplied,	a -ssldir setting is used,  or	other-
	      wise ~/.vnc/certs	is used.

	      This  command  also  creates directories where server and	client
	      certs and	keys will be stored.  The openssl(1) program  must  be
	      installed	on the system and available in PATH.

	      After  the  CA files and directories are created the x11vnc com-
	      mand exits; the VNC server is not	run.

	      You will be prompted for information to put into the CA certifi-
	      cate.   The  info	 does  not have	to be accurate just as long as
	      clients accept the cert for VNC connections.  You	will also need
	      to  supply a passphrase of at least 4 characters for the CA pri-
	      vate key.

	      Once you have generated the CA you can distribute	 its  certifi-
	      cate  part, [dir]/CA/cacert.pem, to other	workstations where VNC
	      viewers will be run.  One	will need to "import" this certificate
	      in the applications, e.g.	Web browser, Java applet plugin, stun-
	      nel, etc.	 Next, you can create and sign keys using the CA  with
	      the -sslGenCert option below.

	      Examples:	 x11vnc	 -sslGenCA  x11vnc -sslGenCA  ~/myCAdir	x11vnc
	      -ssldir ~/myCAdir	-sslGenCA

	      (the last	two lines are equivalent)

       -sslGenCert type	name

	      Generate a VNC server or client certificate and private key pair
	      signed  by  the  CA  created  previously	with  -sslGenCA.   The
	      openssl(1) program must be installed on the system and available
	      in PATH.

	      After  the Certificate is	generated x11vnc exits;	the VNC	server
	      is not run.

	      The type of key to be generated is the string type.  It  is  ei-
	      ther  "server"  (i.e.  for use by	x11vnc)	or "client" (for a VNC
	      viewer).	Note that typically only "server"  is  used:  the  VNC
	      clients authenticate themselves by a non-public-key method (e.g.
	      VNC or unix password).  type is required.

	      An arbitrary default name	you want to associate with the key  is
	      supplied	by  the	name string.  You can change it	at the various
	      prompts when creating the	key.  name is optional.

	      If name is left blank for	clients	keys then  "nobody"  is	 used.
	      If  left	blank  for  server  keys, then the primary server key:
	      "server.pem" is created (this is the  saved  one	referenced  by
	      "-ssl SAVE" when the server is started)

	      If  name	begins with the	string "self:" then a self-signed cer-
	      tificate is created instead of one signed	by your	CA key.

	      If name begins with the string "req:" then only a	key (.key) and
	      a	 certificate  signing *request*	(.req) are generated.  You can
	      then send	the .req file to an external CA	(even  a  professional
	      one,  e.g.  Thawte)  and	then combine the .key and the received
	      cert into	the .pem file with the same basename.

	      The distinction between "server"	and  "client"  is  simply  the
	      choice  of output	filenames and sub-directory.  This makes it so
	      the -ssl SAVE-name option	can easily pick	up the x11vnc PEM file
	      this option generates.  And similarly makes it easy for the -ss-
	      lverify option to	pick up	your client certs.

	      There is nothing special about the filename or  directory	 loca-
	      tion  of either the "server" and "client"	certs.	You can	rename
	      the files	or move	them to	wherever you like.

	      Precede this option with -ssldir [dir] to	use a directory	 other
	      than  the	default	~/.vnc/certs You will need to run -sslGenCA on
	      that directory first before doing	any -sslGenCert	key creation.

	      Note you cannot recreate a cert with exactly the	same  distigu-
	      ished  name (DN) as an existing one.  To do so, you will need to
	      edit the [dir]/CA/index.txt file to delete the line.

	      Similar to -sslGenCA, you	will be	prompted to fill in  some  in-
	      formation	 that  will  be	recorded in the	certificate when it is

	      Tip: if you know the fully-qualified hostname other people  will
	      be  connecting  to,  you	can use	that as	the CommonName "CN" to
	      avoid some applications (e.g. web	browsers and java plugin) com-
	      plaining that it does not	match the hostname.

	      You  will	 also  need to supply the CA private key passphrase to
	      unlock the private key created from -sslGenCA.  This private key
	      is used to sign the server or client certificate.

	      The "server" certs can be	used by	x11vnc directly	by pointing to
	      them via the -ssl	 [pem]	option.	  The  default	file  will  be
	      ~/.vnc/certs/server.pem.	 This one would	be used	by simply typ-
	      ing -ssl SAVE.  The pem file contains both the  certificate  and
	      the private key.	server.crt file	contains the cert only.

	      The  "client" cert + private key file will need to be copied and
	      imported into the	VNC viewer  side  applications	(Web  browser,
	      Java  plugin,  stunnel,  etc.)  Once that	is done	you can	delete
	      the "client" private key file on this machine since it  is  only
	      needed	 on	the    VNC    viewer	side.	  The,	  e.g.
	      ~/.vnc/certs/clients/<name>.pem contains both the	cert and  pri-
	      vate key.	 The <name>.crt	contains the certificate only.

	      NOTE:  It	is very	important to know one should generate new keys
	      with a passphrase.  Otherwise if an untrusted  user  steals  the
	      key  file	he could use it	to masquerade as the x11vnc server (or
	      VNC viewer client).  You will be prompted	whether	to encrypt the
	      key  with	 a  passphrase or not.	It is recommended that you do.
	      One inconvenience	to a passphrase	is that	it must	 be  typed  in
	      EVERY time x11vnc	or the client app is started up.


	      x11vnc -sslGenCert server	x11vnc -ssl SAVE -display :0 ...

	      and  then	 on viewer using ss_vncviewer stunnel wrapper (see the
	      FAQ): ss_vncviewer -verify ./cacert.crt hostname:0

	      (this assumes the	cacert.crt  cert  from	-sslGenCA  was	safely
	      copied to	the VNC	viewer machine where ss_vncviewer is run)

	      Example using a name:

	      x11vnc -sslGenCert server	charlie	x11vnc -ssl SAVE-charlie -dis-
	      play :0 ...

	      Example for a client certificate (rarely used):

	      x11vnc	    -sslGenCert	       client	     roger	   scp
	      ~/.vnc/certs/clients/roger.pem	       somehost:.	    rm

	      x11vnc   is   then   started   with   the	  option    -sslverify
	      ~/.vnc/certs/clients/roger.crt (or simply	-sslverify roger), and
	      on the viewer user on somehost could do for example:

	      ss_vncviewer -mycert ./roger.pem hostname:0

	      If you set the env. var REQ_ARGS='...'  it  will	be  passed  to
	      openssl  req(1).	A common use would be REQ_ARGS='-days 1095' to
	      bump up the expiration date (3 years in this case).

       -sslEncKey pem

	      Utility to encrypt an existing PEM file with  a  passphrase  you
	      supply  when prompted.  For that key to be used (e.g. by x11vnc)
	      the passphrase must be supplied each time.

	      The "SAVE" notation described under -ssl applies as well.	 (pre-
	      cede this	option with -ssldir [dir] to refer a directory besides
	      the default ~/.vnc/certs)

	      The openssl(1) program must  be  installed  on  the  system  and
	      available	 in  PATH.  After the Key file is encrypted the	x11vnc
	      command exits; the VNC server is not run.

	      Examples:	x11vnc -sslEncKey /path/to/foo.pem  x11vnc  -sslEncKey
	      SAVE x11vnc -sslEncKey SAVE-charlie

       -sslCertInfo pem

	      Prints  out information about an existing	PEM file.  In addition
	      the public certificate is	also printed.  The openssl(1)  program
	      must  be	in PATH. Basically the command "openssl	x509 -text" is
	      run on the pem.

	      After the	info is	printed	the  x11vnc  command  exits;  the  VNC
	      server is	not run.

	      The "SAVE" notation described under -ssl applies as well.

	      Using   "LIST"  will  give a list	of all certs being managed (in
	      the ~/.vnc/certs dir, use	-ssldir	 to  refer  to	another	 dir).
	      "ALL" will print out the info for	every managed key (this	can be
	      very long).  Giving a client or server cert shortname will  also
	      try  a  lookup (e.g. -sslCertInfo	charlie).  Use "LISTL" or "LL"
	      for a long (ls -l	style) listing.

	      Using "HASHON" will create  subdirs  [dir]/HASH  and  [dir]/HASH
	      with  OpenSSL hash filenames (e.g. 0d5fbbf1.0) symlinks pointing
	      up to the	corresponding *.crt file.  ([dir] is  ~/.vnc/certs  or
	      one  given  by -ssldir.)	This is	a useful way for other OpenSSL
	      applications (e.g. stunnel) to access all	of the	certs  without
	      having to	concatenate them.  x11vnc will not use them unless you
	      specifically reference them.  "HASHOFF" removes these HASH  sub-

	      The LIST,	LISTL, LL, ALL,	HASHON,	HASHOFF	words can also be low-
	      ercase, e.g. "list".

       -sslDelCert pem

	      Prompts you to delete all	.crt .pem .key .req  files  associated
	      with  [pem].   x11vnc  then  exits.  "SAVE"  and	lookups	 as in
	      -sslCertInfo apply as well.


	      Prints out both the 'genCA' and 'genCert'	x11vnc openssl wrapper
	      scripts  for  you	 to  examine,  modify,	etc.   The scripts are
	      printed to stdout	and then the x11vnc program exits.

       -stunnel	[pem]

	      Use the stunnel(8) ( to	provide	 an  encrypted
	      SSL tunnel between viewers and x11vnc.

	      This  external  tunnel method was	implemented prior to the inte-
	      grated -ssl encryption described above.  It still	works well and
	      avoids  the  requirement	of linking with	the OpenSSL libraries.
	      This mode	requires stunnel to be installed  on  the  system  and
	      available	 via PATH (n.b.	stunnel	is often installed in sbin di-
	      rectories).  Version 4.x of stunnel is assumed (but  see	-stun-
	      nel3 below.)

	      [pem]  is	optional, use "-stunnel	/path/to/stunnel.pem" to spec-
	      ify a PEM	certificate file to pass to stunnel.  See the -ssl op-
	      tion for more info on certificate	files.

	      Whether  or  not your stunnel has	its own	certificate depends on
	      your stunnel configuration; stunnel often	generates one  at  in-
	      stall time.  See your stunnel documentation for details.	In any
	      event, if	you want to use	this certificate you must  supply  the
	      full  path  to it	as [pem].  Note: the file may only be readable
	      by root.

	      [pem] may	 also  be  the	special	 strings  "TMP",  "SAVE",  and
	      "SAVE..."	as described in	the -ssl option.  If [pem] is not sup-
	      plied, "SAVE" is assumed.

	      Note that	the VeNCrypt, ANONTLS, and "ANON" modes	are  not  sup-
	      ported in	-stunnel mode.

	      stunnel  is  started up as a child process of x11vnc and any SSL
	      connections stunnel receives are decrypted and  sent  to	x11vnc
	      over  a  local socket.  The strings "The SSL VNC desktop is ..."
	      and "SSLPORT=..."	 are printed out at startup to indicate	this.

	      The -localhost option is enforced	by  default  to	 avoid	people
	      routing around the SSL channel.  Use -env	STUNNEL_DISABLE_LOCAL-
	      HOST=1 to	disable	this security requirement.

	      Set -env STUNNEL_DEBUG=1 for more	debugging printout.

	      Set -env STUNNEL_PROG=xxx	to the full path  of  stunnel  program
	      you want to be used (e.g.	/usr/bin/stunnel4).

	      Set -env STUNNEL_LISTEN=xxx to the address of the	network	inter-
	      face to listen on	(the default is	to listen on all  interfaces),
	      e.g. STUNNEL_LISTEN=

	      A	simple way to add IPv6 support is STUNNEL_LISTEN=::

	      Your  VNC	 viewer	 will also need	to be able to connect via SSL.
	      Unfortunately not	too many do this.  See the  information	 about
	      SSL  viewers  under the -ssl option.  The	x11vnc project's SSVNC
	      is an option.

	      Also, in the x11vnc distribution,	patched	TightVNC and  UltraVNC
	      Java  applet jar files are provided in the classes/ssl directory
	      that do SSL connections.	Enable serving them  with  the	-http,
	      -http_ssl,  or  -httpdir	(see  the option descriptions for more

	      Note that	for the	Java viewer applet usage the  "?PORT=xxxx"  in
	      the  various URLs	printed	at startup will	need to	be supplied to
	      the web browser to connect properly.

	      Currently	the automatic "single port" HTTPS mode of -ssl is  not
	      fully  supported	in -stunnel mode.  However, it can be emulated

	      %	x11vnc -stunnel	-http_ssl -http_oneport	...

	      In general, it is	also not too difficult to set up an stunnel or
	      other  SSL  tunnel on the	viewer side.  A	simple example on Unix
	      using stunnel 3.x	is:

	      %	stunnel	-c -d localhost:5901 -r	 remotehost:5900  %  vncviewer

	      For  Windows, stunnel has	been ported to it and there are	proba-
	      bly other	such tools available.  See the FAQ and SSVNC for  more

       -stunnel3 [pem]

	      Use  version  3.x	stunnel	command	line syntax instead of version
	      4.x.  The	-http/-httpdir Java applet serving  is	currently  not
	      available	in this	mode.

       -enc cipher:keyfile

	      Use  symmetric  encryption  with	cipher "cipher"	and secret key
	      data in "keyfile".  If keyfile is	pw=<string> then  "string"  is
	      used as the key data.

	      NOTE: It is recommended that you use SSL via the -ssl option in-
	      stead of this option because SSL is well	understood  and	 takes
	      great care to establish unique session keys and is more compati-
	      ble with other software.	Use this option	if you do not want  to
	      deal with	SSL certificates for authentication and	do not want to
	      use SSH but want some encryption for your	VNC  session.	Or  if
	      you  must	 interface with	a symmetric key	tunnel that you	do not
	      have control over.

	      Note that	this mode will NOT work	with the UltraVNC DSM  plugins
	      because  they  alter  the	RFB protocol in	addition to tunnelling
	      with the symmetric cipher	(an unfortunate	choice of  implementa-

	      cipher  can  be one of:  arc4, aesv2, aes-cfb, blowfish, aes256,
	      or 3des.	See the	OpenSSL	documentation for more info.  The key-
	      size is 128 bits (except for aes256).  Here is one way to	make a
	      keyfile with that	many bits:

	      dd if=/dev/random	of=./my.key bs=16 count=1

	      you will need to securely	share this key with the	other side  of
	      the VNC connection (See SSVNC for	examples).

	      Example:	   -enc	  blowfish:./my.key   Example:	  -enc	 blow-

	      By default 16 bytes of random salt followed by 16	bytes of  ran-
	      dom  initialization vector are sent at the very beginning	of the
	      stream.  The other side must read	these and initialize their ci-
	      pher with	them.  These values make the session key unique	(with-
	      out them the security is minimal).  Similarly,  the  other  side
	      must send	us its random salt and IV with those same lengths.

	      The salt and key data are	combined to create a session key using
	      an md5 hash as described in EVP_BytesToKey(3).

	      The exact	call is: EVP_BytesToKey(Cipher,	EVP_md5(), salt,  key-
	      data,  len,  1, keystr, NULL);  where salt is the	random data as
	      described	above, and keydata is  the  shared  secret  key	 data.
	      keystr  is the resulting session key.  The cipher	is then	seeded
	      with keystr and uses the random  initialization  vector  as  its
	      first block.

	      To  modify  the  amount of random	salt and initialization	vector
	      use cipher@n,m where n is	the salt length	and m the  initializa-
	      tion vector length.  E.g.

	      -enc aes-cfb@8,16:./my.key

	      It  is  not  a good idea to set either one to zero, although you
	      may be forced to if the other side of the	tunnel	is  not	 under
	      your control.

	      To  skip the salt	and EVP_BytesToKey MD5 entirely	(no hashing is
	      done: the	keydata	is directly inserted into the cipher)  specify
	      "-1" for the salt, e.g.

	      -enc blowfish@-1,16:./my.key

	      The  message digest can also be changed to something besides the
	      default MD5.  Use	cipher@md+n,m where "md" can be	 one  of  sha,
	      sha1, md5, or ripe.  For example:

	      -enc arc4@sha+8,16:./my.key

	      The  SSVNC  vnc  viewer  project supplies	a symmetric encryption
	      tool named "ultravnc_dsm_helper" that can	be used	on the	viewer
	      side.  For example:

	      ssvncviewer exec='ultravnc_dsm_helper arc4 my.key	0 h:p'

	      where h:p	is the hostname	and port of the	x11vnc server.	ultra-
	      vnc_dsm_helper may also be used standalone to provide a  symmet-
	      ric  encryption  tunnel  for any viewer or server	(VNC or	other-
	      wise.) The cipher	(1st arg) is basically the same	syntax	as  we
	      use above.

	      Also  see	the 'Non-Ultra DSM' SSVNC option for the 'UltraVNC DSM
	      Encryption Plugin' advanced option.

	      For both ways of using the viewer, you can specify the salt,ivec
	      sizes (in	GUI or,	e.g. arc4@8,16).

       -https [port]

	      Use  a  special,	separate  HTTPS	 port (-ssl and	-stunnel modes
	      only) for	HTTPS Java viewer applet downloading.  I.e.  not  5900
	      and not 5800 (the	defaults.)

	      BACKGROUND:  In  -ssl  mode, it turns out	you can	use the	single
	      VNC port (e.g. 5900) for both VNC	and HTTPS connections.	(HTTPS
	      is  used	to  retrieve  a	SSL-aware VncViewer.jar	applet that is
	      provided with x11vnc).  Since both use  SSL  the	implementation
	      was  extended  to	 detect	 if  HTTP traffic (i.e.	GET) is	taking
	      place and	handle it accordingly.	The URL	would be, e.g.:

	      This is convenient for firewalls,	etc,  because  only  one  port
	      needs to be allowed in.  However,	this heuristic adds a few sec-
	      onds delay to each connection and	can be unreliable  (especially
	      if the user takes	much time to ponder the	Certificate dialogs in
	      his browser, Java	VM, or VNC Viewer applet.  That's right	3 sep-
	      arate "Are you sure you want to connect?"	dialogs!)


	      USAGE:  So use the -https	option to provide a separate, more re-
	      liable HTTPS port	that x11vnc will listen	on.  If	[port] is  not
	      provided	(or  is	 0),  one  is autoselected.  The URL to	use is
	      printed out at startup.

	      The SSL Java applet directory is specified via the -httpdir  op-
	      tion.   If  not supplied,	-https will try	to guess the directory
	      as though	the -http option was supplied.

       -httpsredir [port]

	      In -ssl mode with	the Java applet	retrieved via HTTPS, when  the
	      HTML   file   containing	 applet	  parameters  ('index.vnc'  or
	      'proxy.vnc') is sent do NOT set the applet PORT parameter	to the
	      actual  VNC port but set it to "port" instead.  If "port"	is not
	      supplied,	then the port number is	guessed	from  the  Host:  HTTP

	      This  is	useful	when an	incoming TCP connection	redirection is
	      performed	by a router/gateway/firewall from one port to  an  in-
	      ternal  machine  where  x11vnc is	listening on a different port.
	      The Java applet needs to connect to  the	firewall/router	 port,
	      not  the	VNC port on the	internal workstation. For example, one
	      could redir from to workstation:5900.

	      This spares the user from	 having	 to  type  in  https://mygate-	 into their web	browser. Note that port	443 is
	      the default https	port; other ports  must	 be  explicitly	 indi-
	      cated,  for  example:  To
	      avoid having to include the PORT=	in  the	 browser  URL,	simply
	      supply "-httpsredir" to x11vnc.

	      This option does not work	in -stunnel mode.

	      More tricks: set the env var X11VNC_EXTRA_HTTPS_PARAMS to	be ex-
	      tra URL parameters to use.  This way you do not need to  specify
	      extra PARAMS in the index.vnc file.  E.g.	x11vnc -env X11VNC_EX-
	      TRA_HTTPS_PARAMS='?GET=1'	...

	      If you do	not want to expose the non-SSL HTTP port to  the  net-
	      work  (i.e.  you just want the single VNC/HTTPS port, e.g. 5900,
	      open   for   connections)	  then	 specify   the	 option	  -env
	      X11VNC_HTTP_LISTEN_LOCALHOST=1   This  way the connection	to the
	      LibVNCServer httpd server	will only be  available	 on  localhost
	      (note  that in -ssl mode,	HTTPS requests are redirected from SSL
	      to the non-SSL LibVNCServer HTTP server.)


	      For UN-encrypted connections mode	(i.e. no  -ssl,	 -stunnel,  or
	      -enc options), allow the Java VNC	Viewer applet to be downloaded
	      thru the VNC port	via HTTP.

	      That is to say, you can use a single port	for Java applet	viewer
	      connections  by  using  a	URL in your web	browser	like this, for


	      The regular, two-port mode, URL http://hostname:5800  will  con-
	      tinue to work as well.

	      As  mentioned  above,  this  mode	 will  NOT work	with the -ssl,
	      -stunnel,	or -enc	encryption options.  Note that is  it  equiva-
	      lent  to	'-enc none' (i.e. it uses the same detection mechanism
	      as for HTTPS, but	with no	encryption.)

	      HTTPS single-port	is on by default in -ssl encrypted  mode  (and
	      -enc too), so you	only need -http_oneport	when doing non-SSL en-
	      crypted connections.

	      This mode	could also be useful for SSH tunnels  since  it	 means
	      only one port needs to be	redirected.

	      The -httpsredir option may also be useful	for this mode when us-
	      ing an SSH tunnel	as well	as for router port redirections.

	      Note that	the  -env  X11VNC_HTTP_LISTEN_LOCALHOST=1  option  de-
	      scribed  above  under  -httpsredir  applies for the LibVNCServer
	      httpd server in all cases	(ssl or	not.)

       -ssh user@host:disp

	      Create a remote listening	port on	machine	"host" via a SSH  tun-
	      nel using	the -R rport:localhost:lport method. lport will	be the
	      local  x11vnc  listening	port,  so  a   connection   to	 rport
	      (5900+disp) on "host" will reach x11vnc.	E.g.

	      This could be useful if a	firewall/router	prevents incoming con-
	      nections to the x11vnc machine, but the ssh machine  "host"  can
	      be  reached  by the VNC viewer. "user@" is not needed unless the
	      remote unix username differs from	the current one.

	      By default the remote sshd is usually configured to listen  only
	      on  localhost  for rport,	so the viewer may need to ssh -L redir
	      to "host"	as well	(See SSVNC to automate this).  The  sshd  set-
	      ting GatewayPorts	enables	listening on all interfaces for	rport;
	      viewers can reach	it more	easily.

	      "disp" is	the VNC	display	for the	remote SSH side, e.g. 0	corre-
	      sponds to	port 5900, etc.	 If disp is greater than 200 the value
	      is used as the port.  Use	a negative value to force a low	 port,
	      e.g. host:-80 will use port 80.

	      If  ssh-agent  is	 not active, then the ssh password needs to be
	      entered in the terminal where x11vnc is running.

	      By default the remote ssh	will issue a 'sleep 300' to  wait  for
	      the  incoming  connection	 for  5	 mins.	 To  modify  this  use

	      If the remote SSH	server is on a non-standard port (i.e. not 22)
	      use user@host:port:disp+secs.

	      Note  that  the ssh process MAY NOT be killed when x11vnc	exits.
	      It tries by looking at ps(1) output.


	      If no other password method was supplied on  the	command	 line,
	      first  look for ~/.vnc/passwd and	if found use it	with -rfbauth;
	      next, look for ~/.vnc/passwdfile and use	it  with  -passwdfile;
	      otherwise,   prompt   the	  user	 for   a  password  to	create
	      ~/.vnc/passwd and	use it with the	-rfbauth option.  If  none  of
	      these succeed x11vnc exits immediately.

       -storepasswd pass file

	      Store  password pass as the VNC password in the file file.  Once
	      the password is stored the program exits.	 Use the password  via
	      "-rfbauth	file"

	      If  called with no arguments, "x11vnc -storepasswd", the user is
	      prompted	for  a	password  and  it  is  stored  in   the	  file
	      ~/.vnc/passwd.   Called with one argument, that will be the file
	      to store the prompted password in.


	      Disable the big warning message when you use x11vnc without some
	      sort of password.

       -accept string

	      Run  a  command (possibly	to prompt the user at the X11 display)
	      to decide	whether	an incoming client should be allowed  to  con-
	      nect or not.  string is an external command run via system(3) or
	      some special cases described below.  Be sure to quote string  if
	      it contains spaces, shell	characters, etc.  If the external com-
	      mand returns 0 the client	is accepted, otherwise the  client  is
	      rejected.	  See  below for an extension to accept	a client view-

	      If x11vnc	is running as root (say	from inetd(8) or from  display
	      managers xdm(1) ,	gdm(1) , etc), think about the security	impli-
	      cations carefully	before supplying this option (likewise for the
	      -gone option).

	      Environment:  The	RFB_CLIENT_IP environment variable will	be set
	      to the incoming client IP	number and the port in RFB_CLIENT_PORT
	      (or   -1	 if   unavailable).    Similarly,   RFB_SERVER_IP  and
	      RFB_SERVER_PORT (the x11vnc side of the connection), are set  to
	      allow  identification  of	 the  tcp virtual circuit.  The	x11vnc
	      process id will be in RFB_X11VNC_PID,  a	client	id  number  in
	      RFB_CLIENT_ID,  and  the	number	of  other connected clients in
	      RFB_CLIENT_COUNT.	 RFB_MODE will be "accept".  RFB_STATE will be
	      NORMAL, or UNKNOWN indicating up to which	state the  client  has
	      achieved.	  RFB_LOGIN_VIEWONLY  will  be	0, 1, or -1 (unknown).

	      If  string  is "popup" then a builtin popup window is used.  The
	      popup will time out after	120 seconds, use "popup:N"  to	modify
	      the timeout to N seconds (use 0 for no timeout).

	      In the case of "popup" and when the -unixpw option is specified,
	      then a *second* window will be popped up after the user success-
	      fully logs in via	his UNIX password.  This time the user will be
	      identified as UNIX:username@hostname, the	"UNIX:"	 prefix	 indi-
	      cates  which  user  the viewer logged as via -unixpw.  The first
	      popup is only for	whether	to allow him to	even  *try*  to	 login
	      via unix password.

	      If  string  is "xmessage"	then an	xmessage(1) invocation is used
	      for the command.	xmessage must be installed on the machine  for
	      this to work.

	      Both "popup" and "xmessage" will present an option for accepting
	      the client "View-Only" (the client can only watch).  This	option
	      will  not	be presented if	-viewonly has been specified, in which
	      case the entire display is view only.

	      If the user supplied command is  prefixed	 with  something  like
	      "yes:0,no:*,view:3  mycommand  ..." then this associates the nu-
	      merical command return code with the  actions:  accept,  reject,
	      and accept-view-only, respectively.  Use "*" instead of a	number
	      to indicate the default action (in case the command  returns  an
	      unexpected value).  E.g. "no:*" is a good	choice.

	      Note  that  x11vnc blocks	while the external command or popup is
	      running (other clients may see no	updates	during	this  period).
	      So  a person sitting a the physical display is needed to respond
	      to an popup prompt. (use a 2nd x11vnc if you lock	yourself out).

	      More -accept tricks: use "popupmouse" to only allow mouse	clicks
	      in the builtin popup to be recognized.  Similarly	use "popupkey"
	      to only recognize	keystroke responses.  These are	to help	 avoid
	      the  user	accidentally accepting a client	by typing or clicking.
	      All 3 of the popup keywords can be followed by +N+M to supply  a
	      position	for  the  popup	 window.  The default is to center the
	      popup window.

       -afteraccept string

	      As -accept, except to run	a user supplied	command	after a	client
	      has  been	 accepted  and	authenticated. RFB_MODE	will be	set to
	      "afteraccept" and	the other RFB_*	variables are as  in  -accept.
	      Unlike  -accept,	the  command return code is not	interpreted by
	      x11vnc.  Example:	-afteraccept 'killall xlock &'

       -gone string

	      As -accept, except to run	a user supplied	command	when a	client
	      goes away	(disconnects).	RFB_MODE will be set to	"gone" and the
	      other RFB_* variables are	as in -accept.	 The  "popup"  actions
	      apply  as	 well.	Unlike -accept,	the command return code	is not
	      interpreted by x11vnc.  Example: -gone 'xlock &'

       -users list

	      If x11vnc	is started as root (say	from inetd(8) or from  display
	      managers	xdm(1) , gdm(1)	, etc),	then as	soon as	possible after
	      connections to the X display are established try	to  switch  to
	      one  of the users	in the comma separated list.  If x11vnc	is not
	      running as root this option is ignored.

	      Why use this option?  In general it is not needed	 since	x11vnc
	      is  already  connected to	the X display and can perform its pri-
	      mary functions.  The option was added to make some of  the  *ex-
	      ternal* utility commands x11vnc occasionally runs	work properly.
	      In particular under GNOME	 and  KDE  to  implement  the  "-solid
	      color" feature external commands (gconftool-2 and	dcop) unfortu-
	      nately must be run as  the  user	owning	the  desktop  session.
	      Since  this  option  switches  userid it also affects the	userid
	      used to run the processes	for the	-accept	and -gone options.  It
	      also affects the ability to read files for options such as -con-
	      nect, -allow, and	-remap and also	the ultra and tight filetrans-
	      fer  feature  if	enabled.   Note	that the -connect file is also
	      sometimes	written	to.

	      So be careful with this option since in some situations its  use
	      can decrease security.

	      In general the switch to a user will only	take place if the dis-
	      play can still be	successfully opened as that user (this is pri-
	      marily  to  try to guess the actual owner	of the session). Exam-
	      ple: "-users fred,wilma,betty".  Note  that  a  malicious	 local
	      user  "barney"  by  quickly  using "xhost	+" when	logging	in may
	      possibly get the x11vnc process to switch	to user	"fred".	  What
	      happens next?

	      Under  display  managers it may be a long	time before the	switch
	      succeeds (i.e. a user logs in).  To instead make it switch imme-
	      diately  regardless  if  the  display can	be reopened prefix the
	      username with the	"+" character. E.g. "-users +bob"  or  "-users

	      The  latter (i.e.	switching immediately to user "nobody")	is the
	      only obvious use of the -users option that increases security.

	      Use the following	notation to associate a	 group	with  a	 user:
	      user1.group1,user2.group2,...    Note  that  initgroups(2)  will
	      still be called first to try to switch to	ALL of a user's	groups
	      (primary	and  additional	 groups).  Only	if that	fails or it is
	      not available then the single group specified as above  (or  the
	      user's  primary group if not specified) is switched to with set-
	      gid(2).  Use -env	X11VNC_SINGLE_GROUP=1 to prevent trying	 init-
	      groups(2)	 and  only  switch  to the single group.  This sort of
	      setting is only really needed to make the	ultra or  tight	 file-
	      transfer	permissions  work properly. This format	applies	to any
	      comma separated list of users, even the special  "="  modes  de-
	      scribed below.

	      In  -unixpw  mode,  if "-users unixpw=" is supplied then after a
	      user authenticates himself via  the  -unixpw  mechanism,	x11vnc
	      will try to switch to that user as though	"-users	+username" had
	      been supplied.  If you want to limit which users	this  will  be
	      done for,	provide	them as	a comma	separated list after "unixpw="
	      Groups can also be specified as described	above.

	      Similarly, in -ssl mode, if "-users sslpeer=" is	supplied  then
	      after  an	SSL client authenticates with his cert (the -sslverify
	      option is	required for this) x11vnc will extract a UNIX username
	      from  the	 "emailAddress"	 field	(	of the
	      "Subject"	of the x509 SSL	cert and then try to  switch  to  that
	      user  as	though	"-users	 +username" had	been supplied.	If you
	      want to limit which users	this will be done for, provide them as
	      a	 comma	separated  list	 after	"sslpeer=".   Set the env. var
	      X11VNC_SSLPEER_CN	to use the Common Name (normally  a  hostname)
	      instead of the Email field.

	      NOTE:  for sslpeer= mode the x11vnc administrator	must take care
	      that any client certs he adds to -sslverify  have	 the  intended
	      UNIX  username  in the "emailAddress" field of the cert.	Other-
	      wise a user may be able to log in	as another.  This command  can
	      be  of  use  in checking:	"openssl x509 -text -in	file.crt", see
	      the "Subject:" line.  Also, along	with  the  normal  RFB_*  env.
	      vars.   (see   -accept)	passed	 to  external  cmd=  commands,
	      RFB_SSL_CLIENT_CERT will be set to the client's x509 certificate

	      The sslpeer= mode	can aid	finding	X sessions via the FINDDISPLAY
	      and FINDCREATEDISPLAY mechanisms.

	      To immediately switch to a user *before* connections  to	the  X
	      display  are  made  or  any  files opened	use the	"=" character:
	      "-users =bob".  That user	needs to be able to open the X display
	      and any files of course.

	      The  special  user  "guess=" means to examine the	utmpx database
	      (see who(1) ) looking for	a user attached	to the display	number
	      (from DISPLAY or -display	option)	and try	him/her.  To limit the
	      list of guesses, use: "-users guess=bob,betty".

	      Even more	sinister is the	special	user "lurk=" that means	to try
	      to  guess	the DISPLAY from the utmpx login database as well.  So
	      it "lurks" waiting for anyone to log into	an X session and  then
	      connects	to  it.	  Specify a list of users after	the = to limit
	      which users will be tried.   To  enable  a  different  searching
	      mode,  if	 the  first user in the	list is	something like ":0" or
	      ":0-2" that indicates a range of DISPLAY numbers	that  will  be
	      tried (regardless	of whether they	are in the utmpx database) for
	      all users	that are logged	in.  Also see the "-display  WAIT:..."
	      functionality.	Examples:  "-users  lurk="  and	 also  "-users

	      Be especially careful using  the	"guess="  and  "lurk="	modes.
	      They  are	not recommended	for use	on machines with untrustworthy
	      local users.


	      Do not use the MIT-SHM extension for the polling.	  Remote  dis-
	      plays  can  be  polled  this  way: be careful this can use large
	      amounts of network bandwidth.  This is also of use if the	 local
	      machine has a limited number of shm segments and -onetile	is not


	      Sometimes	needed if remotely polled host has  different  endian-
	      ness.  Ignored unless -noshm is set.


	      Do  not use the new copy_tiles() framebuffer mechanism, just use
	      1	shm tile for polling.  Limits shm segments used	to 3.

	      To disable  any  automatic  shm  reduction  set  the  env.  var.

       -solid [color]

	      To  improve  performance,	 when VNC clients are connected	try to
	      change the desktop background to a solid color.  The [color]  is
	      optional:	 the  default  color  is "cyan4".  For a different one
	      specify the X color (rgb.txt name, e.g. "darkblue" or  numerical

	      Currently	 this  option only works on GNOME, KDE,	CDE, XFCE, and
	      classic X	(i.e. with the background image	on the	root  window).
	      The  "gconftool-2",  "dcop" and "xfconf-query" external commands
	      are run for GNOME, KDE, and XFCE respectively.  This also	 works
	      on  native  MacOSX.   (There is no color selection for MacOSX or
	      XFCE.)  Other desktops won't work, (send	us  the	 corresponding
	      commands	if you find them).  If x11vnc is running as root ( in-
	      etd(8) or	gdm(1) ), the -users option may	be needed  for	GNOME,
	      KDE,  XFCE.  If x11vnc guesses your desktop incorrectly, you can
	      force it by  prefixing  color  with  "gnome:",  "kde:",  "cde:",
	      "xfce:", or "root:".

	      Update: -solid no	longer works on	KDE4.

	      This  mode  works	 in a limited way on the Mac OS	X Console with
	      one color	('kelp') using the screensaver writing	to  the	 back-
	      ground.  Look in "~/Library/Screen Savers" for VncSolidColor.png
	      to change	the color.

       -blackout string

	      Black out	rectangles on the screen. string is a comma  separated
	      list  of	WxH+X+Y	type geometries	for each rectangle.  If	one of
	      the items	on the list is the string "noptr"  the	mouse  pointer
	      will not be allowed to go	into a blacked out region.

       -xinerama, -noxinerama

	      If  your	screen is composed of multiple monitors	glued together
	      via XINERAMA, and	that screen is not  a  rectangle  this	option
	      will  try	 to  guess  the	areas to black out (if your system has
	      libXinerama).  default: -xinerama

	      In general, we have noticed on XINERAMA displays you may need to
	      use  the	"-xwarppointer"	option if the mouse pointer misbehaves
	      and it is	enabled	by default. Use	"-noxwarppointer"  if  you  do
	      not want this.


	      Use the DEC-XTRAP	extension for keystroke	and mouse input	inser-
	      tion.  For use on	legacy systems,	e.g. X11R5, running an	incom-
	      plete  or	missing	XTEST extension.  By default DEC-XTRAP will be
	      used if XTEST server grab	control	is missing, use	-xtrap	to  do
	      the keystroke and	mouse insertion	via DEC-XTRAP as well.

       -xrandr [mode]

	      If the display supports the XRANDR (X Resize, Rotate and Reflec-
	      tion) extension, and you expect XRANDR events to	occur  to  the
	      display  while  x11vnc is	running, this options indicates	x11vnc
	      should try to respond to them (as	opposed	to simply crashing  by
	      assuming	the  old  screen size).	 See the xrandr(1) manpage and
	      run 'xrandr -q' for more info.  [mode] is	optional and described

	      Since  watching  for XRANDR events and trapping errors increases
	      polling overhead,	only use this option if	XRANDR changes are ex-
	      pected.  For example on a	rotatable screen PDA or	laptop,	or us-
	      ing a XRANDR-aware Desktop where you resize often.  It  is  best
	      to  be  viewing with a vncviewer that supports the NewFBSize en-
	      coding, since it knows how to  react  to	screen	size  changes.
	      Otherwise,  LibVNCServer tries to	do so something	reasonable for
	      viewers that cannot do this  (portions  of  the  screen  may  be
	      clipped, unused, etc).

	      Note:  the default now is	to check for XRANDR events, but	do not
	      trap every X call	that may fail due  to  resize.	 If  a	resize
	      event is received, the full -xrandr mode is enabled.  To disable
	      even checking for	events supply: -noxrandr.

	      "mode" defaults to "resize", which means create a	new,  resized,
	      framebuffer  and	hope  all  viewers  can	 cope with the change.
	      "newfbsize" means	first disconnect all viewers that do not  sup-
	      port  the	 NewFBSize  VNC	 encoding,  and	then resize the	frame-
	      buffer.  "exit" means disconnect all viewer  clients,  and  then
	      terminate	x11vnc.

       -rotate string

	      Rotate  and/or  flip the framebuffer view	exported by VNC.  This
	      transformation is	independent of XRANDR and is done in  software
	      in  main memory and so may be slower.  This mode could be	useful
	      on a handheld with portrait or landscape modes that do not  cor-
	      respond to the scanline order of the actual framebuffer.	string
	      can be:

	      x	    flip along x-axis y	     flip  along  y-axis  xy	  flip
	      along  x-	 and  y-axes  +90      rotate 90 degrees clockwise -90
	      rotate 90	degrees	counter-clockwise +90x	   rotate  90  degrees
	      CW,  then	 flip along x +90y     rotate 90 degrees CW, then flip
	      along y

	      these give all possible rotations	and reflections.

	      Aliases: same as xy:  yx,	+180, -180, 180	same as	-90: +270, 270
	      same as +90: 90, (ditto for 90x, 90y)

	      Like  -scale,  this transformation is applied at the very	end of
	      any chain	of framebuffer transformations and so any options with
	      geometries,  e.g.	 -blackout,  -clip,  etc.  are relative	to the
	      original X (or -rawfb) framebuffer, not the final	 one  sent  to
	      VNC viewers.

	      If  you do not want the cursor shape to be rotated prefix	string
	      with "nc:", e.g. "nc:+90", "nc:xy", etc.

       -padgeom	WxH

	      Whenever a new vncviewer connects, the framebuffer  is  replaced
	      with  a  fake,  solid black one of geometry WxH.	Shortly	after-
	      wards the	framebuffer is replaced	with the real  one.   This  is
	      intended	for  use with vncviewers that do not support NewFBSize
	      and one wants to make sure the initial viewer geometry  will  be
	      big enough to handle all subsequent resizes (e.g.	under -xrandr,
	      -remote id:windowid, rescaling, etc.)

	      In -unixpw mode this sets	the size of  the  login	 screen.   Use
	      "once:WxH" it ignore padgeom after the login screen is set up.

       -o logfile

	      Write  stderr  messages to file logfile instead of to the	termi-
	      nal.  Same as "-logfile file".  To append	to the file  use  "-oa
	      file"  or	 "-logappend  file".   If  logfile contains the	string
	      "%VNCDISPLAY" it is expanded to the vnc display  (the  name  may
	      need to be guessed at.)  "%HOME" works too.

       -flag file

	      Write  the  "PORT=NNNN" (e.g. PORT=5900) string to file in addi-
	      tion to stdout.  This option could be useful by  wrapper	script
	      to detect	when x11vnc is ready.

       -rmflag file

	      Remove  file at exit to signal when x11vnc is done.  The file is
	      created at startup if it does not	already	exist or  if  file  is
	      prefixed with "create:".	If the file is created,	the x11vnc PID
	      is placed	in the file.  Otherwise	 the  files  contents  is  not
	      changed.	Use prefix "nocreate:" to prevent creation.

       -rc filename

	      Use filename instead of $HOME/.x11vncrc for rc file.


	      Do not process any .x11vncrc file	for options.

       -env VAR=VALUE

	      Set  the	environment  variable 'VAR' to value 'VALUE' at	x11vnc
	      startup.	This is	a convenience utility to  avoid	 shell	script
	      wrappers,	 etc. to set the env. var.  You	may specify as many of
	      these as needed on the command line.

       -prog /path/to/x11vnc

	      Set the full path	to the x11vnc program for cases	when it	cannot
	      be determined from argv[0] (e.g. tcpd/inetd)

       -h, -help

	      Print  this  help	 text.	 -?,  -opts		 Only list the
	      x11vnc options.

       -V, -version

	      Print program version and	last modification date.


	      Print out	license	information.  Same as -copying and -warranty.


	      Instead of exiting after cleaning	up, run	a simple "debug	 crash
	      shell" when fatal	errors are trapped.

       -q, -quiet

	      Be  quiet	 by printing less informational	output to stderr. (use
	      -noquiet to undo an earlier -quiet.)

	      The -quiet option	does not eliminate all	informational  output,
	      it  only	reduces	 it.   It  is  ignored in most auxiliary usage
	      modes,  e.g.  -storepasswd.   To	eliminate  all	 output	  use:
	      2>/dev/null 1>&2,	etc.

       -v, -verbose

	      Print out	more information to stderr.


	      Go  into	the background after screen setup.  Messages to	stderr
	      are lost unless -o logfile is used.  Something like  this	 could
	      be useful	in a script:

	      port=`ssh	-t $host "x11vnc -display :0 -bg" | grep PORT`

	      port=`echo "$port" | sed -e 's/PORT=//'`

	      port=`expr $port - 5900`

	      vncviewer	$host:$port

       -modtweak, -nomodtweak

	      Option  -modtweak	 automatically	tries  to adjust the AltGr and
	      Shift modifiers for differing language keyboards between	client
	      and  host.  Otherwise, only a single key press/release of	a Key-
	      code is simulated	(i.e. ignoring the  state  of  the  modifiers:
	      this usually works for identical keyboards).  Also useful	in re-
	      solving cases where a Keysym is bound to multiple	keys (e.g. "<"
	      +	">" and	"," + "<" keys).  Default: -modtweak

	      If you are having	trouble	with with keys and -xkb	or -noxkb, and
	      similar things don't help, try -nomodtweak.

	      On some HP-UX systems it is been noted that  they	 have  an  odd
	      keymapping  where	a single keycode will have a keysym, e.g. "#",
	      up to three times.  You can check	via "xmodmap -pk" or  the  -dk
	      option.	The failure is when you	try to type "#"	it yields "3".
	      If you see this problem try  setting  the	 environment  variable
	      MODTWEAK_LOWEST=1	to see if it helps.

       -xkb, -noxkb

	      When  in	modtweak  mode,	 use the XKEYBOARD extension (if the X
	      display supports it) to do the modifier tweaking.	 This is  pow-
	      erful and	should be tried	if there are still keymapping problems
	      when using -modtweak by itself.  The default is to check whether
	      some  common keysyms, e.g. !, @, [, are only accessible via -xkb
	      mode and if so then automatically	enable the mode.   To  disable
	      this automatic detection use -noxkb.

	      When  -xkb mode is active	you can	set these env. vars.  They ap-
	      ply only when there is ambiguity as to which key to choose  (i.e
	      the mapping is not one-to-one).  NOKEYHINTS=1: for up ascii key-
	      strokes do not use score hints saved when	the  key  was  pressed
	      down.  NOANYDOWN=1: for up keystrokes do not resort to searching
	      through keys that	are currently pressed down.   KEYSDOWN=N:  re-
	      member  the  last	 N keys	press down for tie-breaking when an up
	      keystroke	comes in.


	      When in -modtweak	(the default) or -xkb mode, if a keysym	in the
	      range A-Z	comes in check the X server to see if the Caps_Lock is
	      set.  If it is do	not artificially press Shift to	 generate  the
	      keysym.	This  will enable the CapsLock key to behave correctly
	      in some circumstances: namely *both* the VNC viewer machine  and
	      the  x11vnc  X server are	in the CapsLock	on state.  If one side
	      has CapsLock on and the other off	and the	keyboard is not	behav-
	      ing  as  you  think  it  should  you should correct the CapsLock
	      states (hint: pressing CapsLock inside and outside of the	viewer
	      can  help	 toggle	them both to the correct state).  However, for
	      best results do not use this option, but	rather	*only*	enable
	      CapsLock	on the VNC viewer side (i.e. by	pressing CapsLock out-
	      side of the viewer window, also -skip_lockkeys below).  Also try
	      -nomodtweak for a	possible workaround.

       -skip_lockkeys, -noskip_lockkeys

	      Have   x11vnc   ignore   all  Caps_Lock,	Shift_Lock,  Num_Lock,
	      Scroll_Lock keysyms received from	 viewers.   The	 idea  is  you
	      press  Caps_Lock on the VNC Viewer side but that does not	change
	      the lock state in	the x11vnc-side	X server.   Nevertheless  your
	      capitalized  letters  come in over the wire and are applied cor-
	      rectly to	the x11vnc-side	X server.   Note  this	mode  probably
	      won't  do	what you want in -nomodtweak mode.  Also, a kludge for
	      KP_n digits is always done in this mode: they are	mapped to reg-
	      ular  digit  keysyms.  See also -capslock	above.	The default is

       -skip_keycodes string

	      Ignore the comma separated list of  decimal  keycodes.   Perhaps
	      these are	keycodes not on	your keyboard but your X server	thinks
	      exist.  Currently	only applies to	-xkb mode.  Use	this option to
	      help  x11vnc in the reverse problem it tries to solve: Keysym ->
	      Keycode(s) when ambiguities exist	(more  than  one  Keycode  per
	      Keysym).	 Run  'xmodmap	-pk' to	see your keymapping.  Example:
	      "-skip_keycodes 94,114"


	      Experimental option that tries to	correct	some "sloppy" key  be-
	      havior.	E.g. if	at the viewer you press	Shift+Key but then re-
	      lease the	Shift before Key that could give  rise	to  extra  un-
	      wanted  characters  (usually only	between	keyboards of different
	      languages).  Only	use this option	if you observe	problems  with
	      some keystrokes.

       -skip_dups, -noskip_dups

	      Some  VNC	viewers	send impossible	repeated key events, e.g. key-
	      down, key-down, key-up, key-up all for the same key, or 20 downs
	      in a row for the same modifier key!  Setting -skip_dups means to
	      skip these duplicates and	just process the  first	 event.	 Note:
	      some  VNC	viewers	assume they can	send down's without the	corre-
	      sponding up's and	so you should not set this  option  for	 these
	      viewers	(symptom:   some  keys	do  not	 autorepeat)  Default:

       -add_keysyms, -noadd_keysyms

	      If a Keysym is received from a VNC viewer	and that  Keysym  does
	      not exist	in the X server, then add the Keysym to	the X server's
	      keyboard mapping on an unused key.  Added	Keysyms	 will  be  re-
	      moved   periodically  and	 also  when  x11vnc  exits.   Default:


	      At startup and exit clear	the modifier keys  by  sending	KeyRe-
	      lease  for  each	one.  The Lock modifiers are skipped.  Used to
	      clear the	state if the display was accidentally  left  with  any
	      pressed down.


	      As  -clear_mods,	except	try  to	release	ANY pressed key.  Note
	      that this	option and -clear_mods can  interfere  with  a	person
	      typing at	the physical keyboard.


	      As  -clear_keys,	except	try  to	release	any CapsLock, NumLock,
	      etc. locks as well.

       -remap string

	      Read Keysym remappings from file named string.   Format  is  one
	      pair of Keysyms per line (can be name or hex value) separated by
	      a	space.	If no file named string	exists,	it is  instead	inter-
	      preted	as    this    form:    key1-key2,key3-key4,...	   See
	      <X11/keysymdef.h>	header file for	a list of Keysym names,	or use

	      To  map a	key to a button	click, use the fake Keysyms "Button1",
	      ..., etc.	E.g: "-remap Super_R-Button2" (useful for pasting on a

	      I	 use  these  if	 the machine I am viewing from does not	have a
	      scrollwheel or I don't like using	the one	it has:

	      -remap Super_R-Button4,Menu-Button5 -remap KP_Add-Button4,KP_En-

	      the former would be used on a PC,	the latter on a	MacBook.  This
	      way those	little used keys can be	used to	generate  bigger  hops
	      than  the	 Up  and  Down arrows provide.	One can	scroll through
	      text or web pages	more quickly this way  (especially  if	x11vnc
	      scroll detection is active.)

	      Use Button44, Button12, etc. for multiple	clicks.

	      To  disable  a keysym (i.e. make it so it	will not be injected),
	      remap it to "NoSymbol" or	"None".

	      Dead keys: "dead"	(or silent, mute) keys are keys	 that  do  not
	      produce  a  character  but  must be followed by a	2nd keystroke.
	      This is often used for accenting characters, e.g.	to put "`"  on
	      top  of  "a"  by	pressing the dead key and then "a".  Note that
	      this interpretation is not part of core X11, it  is  up  to  the
	      toolkit  or  application to decide how to	react to the sequence.
	      The X11 names for	these keysyms are "dead_grave",	 "dead_acute",
	      etc.  However some VNC viewers send the keysyms "grave", "acute"
	      instead thereby disabling	the accenting.	To  work  around  this
	      -remap can be used.  For example "-remap grave-dead_grave,acute-

	      As a convenience,	"-remap	DEAD" applies these remaps:

		    g	  grave-dead_grave
		    a	  acute-dead_acute
		    c	  asciicircum-dead_circumflex
		    t	  asciitilde-dead_tilde
		    m	  macron-dead_macron
		    b	  breve-dead_breve
		    D	  abovedot-dead_abovedot
		    d	  diaeresis-dead_diaeresis
		    o	  degree-dead_abovering
		    A	  doubleacute-dead_doubleacute
		    r	  caron-dead_caron
		    e	  cedilla-dead_cedilla

	      If you just want a subset	 use  the  first  letter  label,  e.g.
	      "-remap  DEAD=ga"	 to  get the first two.	 Additional remaps may
	      also be supplied via commas, e.g.	 "-remap  DEAD=ga,Super_R-But-
	      ton2".   Finally,	"DEAD=missing" means to	apply all of the above
	      as long as the left hand	member	is  not	 already  in  the  X11

       -norepeat, -repeat

	      Option  -norepeat	 disables  X  server  key auto repeat when VNC
	      clients are connected and	VNC keyboard input  is	not  idle  for
	      more  than  5 minutes.  This works around	a repeating keystrokes
	      bug (triggered by	long processing	delays between	key  down  and
	      key  up  client events: either from large	screen changes or high
	      latency).	 Default: -norepeat

	      You can set the env. var.	X11VNC_IDLE_TIMEOUT to the  number  of
	      idle seconds you want (5min = 300secs).

	      Note: your VNC viewer side will likely do	autorepeating, so this
	      is no loss unless	someone	is simultaneously at the real  X  dis-

	      Use  "-norepeat  N" to set how many times	norepeat will be reset
	      if something else	(e.g. X	session	manager) undoes	it.   The  de-
	      fault is 2.  Use a negative value	for unlimited resets.


	      Ignore  video  framebuffer:  only	 process keyboard and pointer.
	      Intended for use with Win2VNC and	x2vnc dual-monitor setups.


	      Do not watch for XBell events. (no beeps will  be	 heard)	 Note:
	      XBell monitoring requires	the XKEYBOARD extension.


	      Do  not  manage  exchange	 of  X selection/cutbuffer between VNC
	      viewers and the X	server at all.


	      Do not poll the PRIMARY selection	for changes to	send  back  to
	      clients.	(PRIMARY is still set on received changes, however).


	      Do  not  set the PRIMARY selection for changes received from VNC


	      Do not poll the CLIPBOARD	selection for changes to send back  to
	      clients.	(CLIPBOARD is still set	on received changes, however).


	      Do not set the CLIPBOARD selection for changes received from VNC

       -seldir string

	      If direction string is "send", only send the selection to	 view-
	      ers,  and	if it is "recv"	only receive it	from viewers.  To work
	      around apps setting the selection	too frequently and messing  up
	      the  other  end.	You can	actually supply	a comma	separated list
	      of directions, including "debug" to turn on debugging output.

       -cursor [mode], -nocursor

	      Sets how the pointer cursor shape	 (little  icon	at  the	 mouse
	      pointer)	should	be handled.  The "mode"	string is optional and
	      is described below.  The default is to show some sort of	cursor
	      shape(s).	  How this is done depends on the VNC viewer and the X
	      server.  Use -nocursor to	disable	cursor shapes completely.

	      Some VNC viewers support the TightVNC CursorPosUpdates and  Cur-
	      sorShapeUpdates  extensions (cuts	down on	network	traffic	by not
	      having to	send the  cursor  image	 every	time  the  pointer  is
	      moved),  in which	case these extensions are used (see -nocursor-
	      shape and	-nocursorpos below to disable).	 For other viewers the
	      cursor  shape  is	written	directly to the	framebuffer every time
	      the pointer is moved or changed and gets	sent  along  with  the
	      other framebuffer	updates.  In this case,	there will be some lag
	      between the vnc viewer pointer and the remote cursor position.

	      If the X display supports	retrieving the cursor  shape  informa-
	      tion  from  the  X server, then the default is to	use that mode.
	      On Solaris this can be done with	the  SUN_OVL  extension	 using
	      -overlay	(see  also  the	 -overlay_nocursor option).  A similar
	      overlay scheme is	used on	IRIX.  Xorg (e.g.  Linux)  and	recent
	      Solaris  Xsun  servers  support the XFIXES extension to retrieve
	      the exact	cursor shape from the X	server.	 If XFIXES is  present
	      it  is  preferred	over Overlay and is used by default (see -nox-
	      fixes below).  This can be disabled  with	 -nocursor,  and  also
	      some values of the "mode"	option below.

	      Note that	under XFIXES cursors with transparency (alpha channel)
	      will usually not be exactly represented and one may find Overlay
	      preferable.  See also the	-alphacut and -alphafrac options below
	      as fudge factors to try to improve  the  situation  for  cursors
	      with transparency	for a given theme.

	      The  "mode"  string  can	be used	to fine-tune the displaying of
	      cursor shapes.  It can be	used the following ways:

	      "-cursor arrow" -	just show the standard arrow nothing  more  or
	      nothing less.

	      "-cursor none" - same as "-nocursor"

	      "-cursor	X" - when the cursor appears to	be on the root window,
	      draw the familiar	X shape.  Some desktops	such as	GNOME cover up
	      the root window completely, and so this will not work, try "X1",
	      etc, to try to shift the tree depth.  On high latency  links  or
	      slow  machines there will	be a time lag between expected and the
	      actual cursor shape.

	      "-cursor some" - like "X"	but use	additional heuristics  to  try
	      to  guess	if the window should have a windowmanager-like resizer
	      cursor or	a text input I-beam cursor.  This is a complete	 hack,
	      but  may be useful in some situations because it provides	a lit-
	      tle more feedback	about the cursor shape.

	      "-cursor most" - try to show as many cursors as possible.	 Often
	      this  will  only	be  the	 same as "some"	unless the display has
	      overlay visuals or XFIXES	extensions available.  On Solaris  and
	      IRIX  if	XFIXES	is  not	 available,  -overlay mode will	be at-


	      Show cursor shape	changes	even when the mouse is	being  dragged
	      with a mouse button down.	 This is useful	if you want to be able
	      to see Drag-and-Drop cursor icons, etc.

       -arrow n

	      Choose an	alternate "arrow" cursor from a	 set  of  some	common
	      ones.   n	 can  be 1 to 6.  Default is: 1	Ignored	when in	XFIXES
	      cursor-grabbing mode.


	      Do not use the XFIXES extension to draw the exact	 cursor	 shape
	      even if it is available.

	      Note:  To	 work around a crash in	Xorg 1.5 and later some	people
	      needed to	use -noxfixes.	The Xorg crash occurred	right after  a
	      Display Manager (e.g. GDM) login.	 Starting with x11vnc 0.9.9 it
	      tries to automatically avoid using XFIXES	until  it  is  sure  a
	      window manager is	running.  See the -reopen option for more info
	      and how to use X11VNC_AVOID_WINDOWS=never	to disable it.

       -alphacut n

	      When using the XFIXES extension for the  cursor  shape,  cursors
	      with  transparency  will	not  usually be	displayed exactly (but
	      opaque ones will).  This option sets n as	a cutoff  for  cursors
	      that have	transparency ("alpha channel" with values ranging from
	      0	to 255)	Any cursor pixel with alpha value less than n  becomes
	      completely  transparent.	 Otherwise  the	 pixel	is  completely
	      opaque.  Default 240

       -alphafrac fraction

	      With the threshold in -alphacut some cursors will	become	almost
	      completely  transparent  because their alpha values are not high
	      enough.  For those cursors  adjust  the  alpha  threshold	 until
	      fraction	of  the	 non-zero  alpha channel pixels	become opaque.
	      Default 0.33


	      By default, XFIXES cursors pixels	with transparency have the al-
	      pha  factor multiplied into the RGB color	values (i.e. that cor-
	      responding to blending the  cursor  with	a  black  background).
	      Specify  this  option  to	 remove	 the alpha factor. (useful for
	      light colored semi-transparent cursors).


	      In XFIXES	mode do	not send cursor	alpha channel data to  LibVNC-
	      Server.	The default is to send it.  The	alphablend effect will
	      only be visible in -nocursorshape	mode or	for clients with  cur-
	      sorshapeupdates  turned  off. (However there is a	hack for 32bpp
	      with depth 24, it	uses the extra 8 bits to store	cursor	trans-
	      parency  for use with a hacked vncviewer that applies the	trans-
	      parency locally.	See the	FAQ for	more info).


	      Do not use the TightVNC  CursorShapeUpdates  extension  even  if
	      clients support it.  See -cursor above.

       -cursorpos, -nocursorpos

	      Option  -cursorpos enables sending the X cursor position back to
	      all vnc clients that support the TightVNC	 CursorPosUpdates  ex-
	      tension.	Other clients will be able to see the pointer motions.
	      Default: -cursorpos

       -xwarppointer, -noxwarppointer

	      Move the pointer with XWarpPointer(3X) instead of	the XTEST  ex-
	      tension.	Use this as a workaround if the	pointer	motion behaves
	      incorrectly, e.g.	 on touchscreens or other non-standard setups.

	      It is also sometimes needed on XINERAMA displays and is  enabled
	      by  default if XINERAMA is found to be active.  To prevent this,
	      use -noxwarppointer.


	      Even if there is no displacement (dx = dy	= 0) for a  VNC	 mouse
	      event  force  the	 pointer to the	indicated x,y position anyway.
	      Recent (2009) gui	toolkits (gnome) have problems	with  x11vnc's
	      original	mouse input injection method.  So x11vnc's mouse input
	      injection	method has been	modified.  To regain the OLD  behavior
	      use  this	option:	-always_inject.	 Then x11vnc will always force
	      positioning the mouse to the x,y position	even if	that  position
	      has not changed since the	previous VNC input event.

	      The  first place this problem was	noticed	was in gnome terminal:
	      if you pressed and released mouse	button 3, a  menu  was	posted
	      and  then	its first element 'New Terminal	Window'	was activated.
	      This was because x11vnc injected the mouse position twice:  once
	      on  ButtonPress  and again on ButtonRelease.  The	toolkit	inter-
	      preted the 2nd one as mouse motion even though the mouse	hadn't
	      moved.   So  now	by default x11vnc tries	to avoid injecting the
	      2nd one.

	      Note that	with the new default x11vnc will be oblivious  to  ap-
	      plications moving	the pointer (warping) or the user at the phys-
	      ical display moving it.  So it might, e.g., inject ButtonRelease
	      at  the  wrong  position.	 If this (or similar scenarios)	causes
	      problems in your environment, specify -always_inject for the old

       -buttonmap string

	      String  to remap mouse buttons.  Format: IJK-LMN,	this maps but-
	      tons I ->	L, etc., e.g.  -buttonmap 13-31

	      Button presses can also be mapped	to keystrokes: replace a  but-
	      ton   digit   on	 the   right  of  the  dash  with  :<sym>:  or
	      :<sym1>+<sym2>: etc. for multiple	 keys.	For  example,  if  the
	      viewing  machine	has a mouse-wheel (buttons 4 5)	but the	x11vnc
	      side does	not, these will	do scrolls:

	      -buttonmap 12345-123:Prior::Next:

	      -buttonmap 12345-123:Up+Up+Up::Down+Down+Down:

	      See <X11/keysymdef.h> header file	for a list of Keysyms, or  use
	      the  xev(1)  program.  Note: mapping of button clicks to Keysyms
	      may not work if -modtweak	or -xkb	is needed for the Keysym.

	      If you include a modifier	like "Shift_L" the modifier's  up/down
	      state is toggled,	e.g. to	send "The" use :Shift_L+t+Shift_L+h+e:
	      (the 1st one is shift down and the 2nd one is shift up).	(note:
	      the  initial  state of the modifier is ignored and not reset) To
	      include button events use	"Button1", ... etc.

	      -buttonmap currently does	not  work  on  MacOSX  console	or  in
	      -rawfb mode.

	      Workaround:  use -buttonmap IJ...-LM...=n	to limit the number of
	      mouse buttons to n, e.g. 123-123=3.  This	 will  prevent	x11vnc
	      from  crashing  if the X server reports there are	5 buttons (4/5
	      scroll wheel), but there are only	really 3.


	      Do not update the	display	during mouse  dragging	events	(mouse
	      button  held  down).   Greatly improves response on slow setups,
	      but you lose all visual feedback for drags, text selection,  and
	      some menu	traversals.  It	overrides any -pointer_mode setting.

       -ncache n

	      Client-side  caching  scheme.  Framebuffer memory	n (an integer)
	      times that of the	full display is	 allocated  below  the	actual
	      framebuffer  to cache screen contents for	rapid retrieval.  So a
	      W	x H frambuffer is expanded to a	W x (n+1)*H  one.   Use	 0  to

	      The n is actually	optional, the default is 10.

	      For this and the other -ncache* options below you	can abbreviate
	      "-ncache"	with "-nc".  Also, "-nonc" is the same as "-ncache 0"

	      This is an experimental option, currently	implemented in an awk-
	      ward  way	 in that in the	VNC Viewer you can see the pixel cache
	      contents if you scroll down, etc.	  So  you  will	 have  to  set
	      things  up so you	can't see that region.	If this	method is suc-
	      cessful, the changes required for	clients	to do this  less  awk-
	      wardly will be investigated.

	      The  SSVNC  viewer  does	a good job at automatically hiding the
	      pixel cache region.  Or use SSVNC's -ycrop option	to  explicitly
	      hide the region.

	      Note  that  this	mode consumes a	huge amount of memory, both on
	      the x11vnc server	side and on the	VNC Viewer side.  If n=2  then
	      the  amount  of  RAM used	is roughly tripled for both x11vnc and
	      the VNC Viewer.  As a rule of  thumb,  note  that	 1280x1024  at
	      depth 24 is about	5MB of pixel data.

	      For  reasonable response when cycling through 4 to 6 large (e.g.
	      web browser) windows a value  n  of  6  to  12  is  recommended.
	      (that's right: ~10X more memory...)

	      Because of the way window	backingstore and saveunders are	imple-
	      mented, n	must be	even.  It will be incremented by 1  if	it  is

	      This  mode  also works for native	MacOS X, but may not be	as ef-
	      fective as the X version.	 This is due to	a  number  of  things,
	      one  is the drop-shadow compositing that leaves extra areas that
	      need to be repaired (see -ncache_pad).  Another  is  the	window
	      iconification  animations	need to	be avoided (see	-macicontime).
	      It appears the that the 'Scale' animation	mode gives better  re-
	      sults than the 'Genie' one.  Also, window	event detection	not as
	      accurate as the X	version.


	      In -ncache mode, try to do copyrect  opaque  window  moves/drags
	      instead  of  wireframes  (this can induce	painting errors).  The
	      wireframe	will still be used when	moving a window	whose save-un-
	      ders has not yet been set	or has been invalidated.

	      Some  VNC	 Viewers provide better	response than others with this
	      option.  On Unix,	 realvnc  viewer  gives	 smoother  drags  than
	      tightvnc viewer.	Response may also be choppy if the server side
	      machine is too slow.

	      Sometimes	on very	slow modem connections,	this actually gives an
	      improvement  because no pixel data at all	(not even the box ani-
	      mation) is sent during the drag.


	      In -ncache mode, do not assume that moving a window  will	 cause
	      the window manager to raise it to	the top	of the stack.  The de-
	      fault is to assume it does, and so at the	beginning of any wire-
	      frame, etc, window moves the window will be pushed to top	in the
	      VNC viewer.


	      In -ncache mode, do not try to guess when	the desktop (viewport)
	      changes  to another one (i.e. another workarea).	The default is
	      to try to	guess and when detected	try to	make  the  transistion
	      more smoothly.


	      In  -ncache  mode, do not	try to snapshot	the desktop background
	      to use in	guessing or reconstructing window save-unders.


	      In -ncache mode, do not try to disable window manager animations
	      and  other  effects  (that usually degrade ncache	performance or
	      cause painting errors).  The default is to try to	 disable  them
	      on KDE (but not GNOME) when VNC clients are connected.

	      For  other  window managers or desktops that provide animations,
	      effects, compositing, translucency, etc. that interfere with the
	      -ncache method you will have to disable them manually.


	      In  -ncache  mode,  enable  some heuristics for old style	window
	      managers such as fvwm and	twm.

       -ncache_pad n

	      In -ncache mode, pad each	window with n pixels for  the  caching
	      rectangles.   This  can  be used to try to improve the situation
	      with dropshadows or other	compositing (e.g. MacOS	X window  man-
	      ager), although it could make things worse.  The default is 0 on
	      Unix and 24 on MacOS X.


	      Turn on debugging	and profiling output under -ncache.

       -wireframe [str], -nowireframe

	      Try to detect window moves or resizes when  a  mouse  button  is
	      held  down  and show a wireframe instead of the full opaque win-
	      dow.  This is based completely on	heuristics and may not	always
	      work:  it	 depends  on your window manager and even how you move
	      things around.  See -pointer_mode	below for  discussion  of  the
	      "bogging down" problem this tries	to avoid.  Default: -wireframe

	      Shorter aliases:	-wf [str]  and -nowf

	      The  value "str" is optional and,	of course, is packed with many
	      tunable parameters for this scheme:

	      Format: shade,linewidth,percent,T+B+L+R,mod,t1+t2+t3+t4 Default:

	      If  you  leave nothing between commas: ",," the default value is
	      used.  If	you don't specify enough commas, the trailing  parame-
	      ters are set to their defaults.

	      "shade"  indicate	 the  "color"  for  the	 wireframe,  usually a
	      greyscale: 0-255,	however	for 16 and 32bpp you  can  specify  an
	      rgb.txt  X color (e.g. "dodgerblue") or a	value >	255 is treated
	      as RGB (e.g. red is 0xff0000).  "linewidth" sets	the  width  of
	      the  wireframe  in pixels.  "percent" indicates to not apply the
	      wireframe	scheme to windows with area less than this percent  of
	      the full screen.

	      "T+B+L+R"	 indicates  four  integers for how close in pixels the
	      pointer has to be	from the Top, Bottom, Left, or Right edges  of
	      the  window  to  consider	 wireframing.	This  is  a speedup to
	      quickly exclude a	window from being wireframed: set them all  to
	      zero  to	not try	the speedup (scrolling and selecting text will
	      likely be	slower).

	      "mod" specifies if a button down event in	the  interior  of  the
	      window  with a modifier key (Alt,	Shift, etc.) down should indi-
	      cate a wireframe opportunity.  It	can be "0" or "none"  to  skip
	      it, "1" or "all" to apply	it to any modifier, or "Shift",	"Alt",
	      "Control", "Meta", "Super", or "Hyper" to	only  apply  for  that
	      type of modifier key.

	      "t1+t2+t3+t4"  specify  four floating point times	in seconds: t1
	      is how long to wait for the pointer to move, t2 is how  long  to
	      wait  for	 the window to start moving or being resized (for some
	      window managers this can be rather long),	t3 is how long to keep
	      a	wireframe moving before	repainting the window. t4 is the mini-
	      mum time between sending wireframe "animations".	If a slow link
	      is  detected, these values may be	automatically changed to some-
	      thing better for a slow link.


	      By default, mouse	motion and button presses of a user sitting at
	      the  LOCAL  display  are monitored for wireframing opportunities
	      (so that the  changes  will  be  sent  efficiently  to  the  VNC
	      clients).	 Use this option to disable this behavior.

       -wirecopyrect mode, -nowirecopyrect

	      Since  the  -wireframe mechanism evidently tracks	moving windows
	      accurately, a speedup can	be obtained by telling the VNC viewers
	      to  locally  copy	the translated window region.  This is the VNC
	      CopyRect encoding: the framebuffer update	doesn't	need  to  send
	      the actual new image data.

	      Shorter aliases:	-wcr [mode]  and -nowcr

	      "mode" can be "never" (same as -nowirecopyrect) to never try the
	      copyrect,	"top" means only do it if the window was  not  covered
	      by  any  other  windows,	and  "always"  means  to translate the
	      orginally	unobscured region (this	may look odd as	the  remaining
	      pieces come in, but helps	on a slow link).  Default: "always"

	      Note:  there  can	be painting errors or slow response when using
	      -scale so	you may	want to	disable	CopyRect in this case  "-wire-
	      copyrect	never"	on  the	command	line or	by remote-control.  Or
	      you can also use the "-scale xxx:nocr" scale option.


	      Turn on debugging	info printout for  the	wireframe  heuristics.
	      "-dwf" is	an alias.  Specify multiple times for more output.

       -scrollcopyrect mode, -noscrollcopyrect

	      Like -wirecopyrect, but use heuristics to	try to guess if	a win-
	      dow has scrolled its contents  (either  vertically  or  horizon-
	      tally).	This  requires	the RECORD X extension to "snoop" on X
	      applications (currently for certain XCopyArea and	XConfigureWin-
	      dow  X protocol requests).  Examples: Hitting <Return> in	a ter-
	      minal window when	the cursor was at the bottom, the text scrolls
	      up  one line.  Hitting <Down> arrow in a web browser window, the
	      web page scrolls up a small amount.  Or scrolling	with a scroll-
	      bar or mouse wheel.

	      Shorter aliases:	-scr [mode]  and -noscr

	      This  scheme  will  not  always detect scrolls, but when it does
	      there is a nice speedup from using  the  VNC  CopyRect  encoding
	      (see  -wirecopyrect).   The  speedup  is both in reduced network
	      traffic and reduced X framebuffer	polling/copying.  On the other
	      hand, it may induce undesired transients (e.g. a terminal	cursor
	      being scrolled up	when it	should not be) or other	 painting  er-
	      rors  (window  tearing,  bunching-up, etc).  These are automati-
	      cally repaired in	a short	period of time.	 If this is  unaccept-
	      able disable the feature with -noscrollcopyrect.

	      Screen  clearing	kludges:  for testing at least,	there are some
	      "magic key sequences" (must be done in less than	1  second)  to
	      aid  repairing  painting errors that may be seen when using this

	      3	Alt_L's	  in a row: resend whole screen, 4 Alt_L's   in	a row:
	      reread and resend	whole screen, 3	Super_L's in a row: mark whole
	      screen for polling, 4 Super_L's in a row:	reset RECORD  context,
	      5	Super_L's in a row: try	to push	a black	screen

	      note:  Alt_L is the Left "Alt" key (a single key)	Super_L	is the
	      Left "Super" key (Windows	flag).	Both  of  these	 are  modifier
	      keys,  and  so  should  not  generate characters when pressed by
	      themselves.  Also, your VNC viewer may have its own refresh hot-
	      key or button.

	      "mode"  can  be "never" (same as -noscrollcopyrect) to never try
	      the copyrect, "keys" means to try	it in response	to  keystrokes
	      only,  "mouse" means to try it in	response to mouse events only,
	      "always" means to	do both. Default: "always"

	      Note: there can be painting errors or slow response  when	 using
	      -scale  so  you  may  want  to  disable  CopyRect	 in  this case
	      "-scrollcopyrect never" on the command line  or  by  remote-con-
	      trol.  Or	you can	also use the "-scale xxx:nocr" scale option.

       -scr_area n

	      Set  the minimum area in pixels for a rectangle to be considered
	      for the -scrollcopyrect detection	 scheme.   This	 is  to	 avoid
	      wasting the effort on small rectangles that would	be quickly up-
	      dated the	normal way.  E.g. suppose an app updated the  position
	      of  its  skinny scrollbar	first and then shifted the large panel
	      it controlled.  We want to be sure to skip the  small  scrollbar
	      and get the large	panel. Default:	60000

       -scr_skip list

	      Skip  scroll detection for applications matching the comma sepa-
	      rated list of strings  in	 list.	 Some  applications  implement
	      their  scrolling	in strange ways	where the XCopyArea, etc, also
	      applies to invisible portions of	the  window:  if  we  CopyRect
	      those  areas  it	looks awful during the scroll and there	may be
	      painting errors left after the scroll.  Soffice.bin is the worst
	      known offender.

	      Use  "##"	 to  denote  the  start	of the application class (e.g.
	      "##XTerm") and "++" to denote the	start of the  application  in-
	      stance  name  (e.g. "++xterm").  The string your list is matched
	      against is of the	form "^^WM_NAME##Class++Instance<same-for-any-
	      subwindows>"  The	 "xlsclients  -la"  command  will provide this

	      If a pattern is prefixed with "KEY:" it  only  applies  to  Key-
	      stroke  generated	 scrolls  (e.g.	 Up arrow).  If	it is prefixed
	      with "MOUSE:" it only applies to	Mouse  induced	scrolls	 (e.g.
	      dragging	on  a  scrollbar).   Default:  ##Soffice.bin,##StarOf-

       -scr_inc	list

	      Opposite of -scr_skip: this list is consulted first and if there
	      is  a  match the window will be monitored	via RECORD for scrolls
	      irrespective of -scr_skip.  Use -scr_skip	'*' to	skip  anything
	      that  does not match your	-scr_inc.  Use -scr_inc	'*' to include

       -scr_keys list

	      For keystroke scroll detection, only apply the RECORD heuristics
	      to  the  comma  separated	list of	keysyms	in list.  You may find
	      the RECORD overhead for every one	of  your  keystrokes  disrupts
	      typing  too  much,  but you don't	want to	turn it	off completely
	      with "-scr mouse"	and -scr_parms does not	work or	is too confus-

	      The  listed  keysyms  can	 be numeric or the keysym names	in the
	      <X11/keysymdef.h>	header file or from the	xev(1) program.	 Exam-
	      ple: "-scr_keys Up,Down,Return".	One probably wants to have ap-
	      plication	specific lists (e.g. for terminals, etc) but  that  is
	      too icky to think	about for now...

	      If  list	begins	with the "-" character the list	is taken as an
	      exclude list: all	keysyms	except those list will be  considered.
	      The  special  string  "builtin"  expands	to an internal list of
	      keysyms that are likely to cause scrolls.	 BTW, by default modi-
	      fier  keys,  Shift_L, Control_R, etc, are	skipped	since they al-
	      most never induce	scrolling by themselves.

       -scr_term list

	      Yet another cosmetic kludge.  Apply shell/terminal heuristics to
	      applications   matching	comma  separated  list	(same  as  for
	      -scr_skip/-scr_inc).  For	example	an  annoying  transient	 under
	      scroll  detection	 is  if	you hit	Enter in a terminal shell with
	      full text	window,	the solid text cursor block will  be  scrolled
	      up.   So	for a short time there are two (or more) block cursors
	      on the screen.  There are	similar	 scenarios,  (e.g.  an	output
	      line is duplicated).

	      These  transients	are induced by the approximation of scroll de-
	      tection (e.g. it detects the scroll, but not the fact  that  the
	      block cursor was cleared just before the scroll).	 In nearly all
	      cases these transient errors are repaired	when the true X	frame-
	      buffer  is  consulted  by	the normal polling.  But they are dis-
	      tracting,	so what	this option provides is	extra  "padding"  near
	      the  bottom  of  the terminal window: a few extra	lines near the
	      bottom will not be scrolled, but rather updated from the	actual
	      X	 framebuffer.	This  usually  reduces the annoying artifacts.
	      Use "none" to disable.  Default: "term"

       -scr_keyrepeat lo-hi

	      If a key is held down (or	otherwise repeats  rapidly)  and  this
	      induces  a rapid sequence	of scrolls (e.g. holding down an Arrow
	      key) the "scrollcopyrect"	detection and overhead may not be able
	      to  keep up.  A time per single scroll estimate is performed and
	      if that estimate predicts	a sustainable scrollrate of  keys  per
	      second  between  "lo"  and  "hi" then repeated keys will be DIS-
	      CARDED to	maintain the scrollrate. For example your key  autore-
	      peat  may	 be  25	 keys/sec, but for a large window or slow link
	      only 8 scrolls per second	can be sustained, then roughly	2  out
	      of  every	 3 repeated keys will be discarded during this period.
	      Default: "4-20"

       -scr_parms string

	      Set various parameters for the scrollcopyrect mode.  The	format
	      is similar to that for -wireframe	and packed with	lots of	param-

	      Format:	      T+B+L+R,t1+t2+t3,s1+s2+s3+s4+s5	      Default:

	      If  you  leave nothing between commas: ",," the default value is
	      used.  If	you don't specify enough commas, the trailing  parame-
	      ters are set to their defaults.

	      "T+B+L+R"	 indicates  four  integers for how close in pixels the
	      pointer has to be	from the Top, Bottom, Left, or Right edges  of
	      the  window  to consider scrollcopyrect.	If -wireframe overlaps
	      it takes precedence.  This is a speedup  to  quickly  exclude  a
	      window  from  being  watched for scrollcopyrect: set them	all to
	      zero to not try the speedup (things  like	 selecting  text  will
	      likely be	slower).

	      "t1+t2+t3"  specify  three  floating point times in seconds that
	      apply to scrollcopyrect detection	with *Keystroke* input:	t1  is
	      how long to wait after a key is pressed for the first scroll, t2
	      is how long to keep looking after	a Keystroke  scroll  for  more
	      scrolls.	 t3  is	 how  frequently  to try to update surrounding
	      scrollbars outside of the	scrolling area (0.0 to disable)

	      "s1+s2+s3+s4+s5" specify five floating point  times  in  seconds
	      that apply to scrollcopyrect detection with *Mouse* input: s1 is
	      how long to wait after a mouse button is pressed for  the	 first
	      scroll,  s2  is  how long	to keep	waiting	for additional scrolls
	      after the	first Mouse scroll was detected.  s3 is	how frequently
	      to try to	update surrounding scrollbars outside of the scrolling
	      area (0.0	to disable).  s4 is how	long to	buffer pointer	motion
	      (to  try	to get fewer, bigger mouse scrolls). s5	is the maximum
	      time to spend just updating the scroll window  without  updating
	      the rest of the screen.

       -fixscreen string

	      Periodically  "repair"  the  screen based	on settings in string.
	      Hopefully	you won't need this option, it is intended  for	 cases
	      when  the	 -scrollcopyrect  or  -wirecopyrect features leave too
	      many painting errors, but	it can be used for any scenario.  This
	      option  periodically  performs costly operations and so interac-
	      tive response may	be reduced when	it  is	on.   You  can	use  3
	      Alt_L's  (the  Left "Alt"	key) taps in a row (as described under
	      -scrollcopyrect) instead to manually request  a  screen  repaint
	      when it is needed.

	      string  is  a comma separated list of one	or more	of the follow-
	      ing: "V=t", "C=t", "X=t",	and "8=t".  In these "t" stands	for  a
	      time  in	seconds	(it is a floating point	even though one	should
	      usually use values > 2 to	avoid wasting resources).  V sets  how
	      frequently  the  entire  screen should be	sent to	viewers	(it is
	      like the 3 Alt_L's).  C sets how long to wait after  a  CopyRect
	      to repaint the full screen.  X sets how frequently to reread the
	      full X11 framebuffer from	the X server and push it out  to  con-
	      nected viewers.  Use of X	should be rare,	please report a	bug if
	      you find you need	it. 8= applies only for	-8to24 mode:  it  sets
	      how  often  the  non-default  visual regions of the screen (e.g.
	      8bpp  windows)  are  refreshed.	 Examples:   -fixscreen	  V=10
	      -fixscreen C=10


	      Turn  on	debugging  info	 printout  for	the scroll heuristics.
	      "-ds" is an alias.  Specify it multiple times for	more output.


	      Disable any use of the RECORD extension.	This is	currently used
	      by the -scrollcopyrect scheme and	to monitor X server grabs.

       -grab_buster, -nograb_buster

	      Some  of the use of the RECORD extension can leave a tiny	window
	      for XGrabServer deadlock.	 This  is  only	 if  the  whole-server
	      grabbing	application expects mouse or keyboard input before re-
	      leasing the grab.	 It is usually	a  window  manager  that  does
	      this.   x11vnc  takes  care  to avoid the	problem, but if	caught
	      x11vnc will freeze.  Without -grab_buster, the only solution  is
	      to go the	physical display and give it some input	to satisfy the
	      grabbing app.  Or	manually kill and restart the  window  manager
	      if  that	is  feasible.	With  -grab_buster, x11vnc will	fork a
	      helper thread and	if x11vnc appears to be	stuck in a grab	 after
	      a	 period	 of time (20-30	sec) then it will inject some user in-
	      put: button clicks, Escape, mouse	motion,	etc to	try  to	 break
	      the  grab.  If you experience a lot of grab deadlock, please re-
	      port a bug.


	      Turn on debugging	info printout with  respect  to	 XGrabServer()
	      deadlock for -scrollcopyrect__mode_.


	      Turn  on	debugging info printout	with respect to	PRIMARY, CLIP-
	      BOARD, and CUTBUFFER0 selections.

       -pointer_mode n

	      Various pointer motion update schemes. "-pm" is an  alias.   The
	      problem is pointer motion	can cause rapid	changes	on the screen:
	      consider the rapid changes when you drag a large	window	around
	      opaquely.	  Neither  x11vnc's screen polling and vnc compression
	      routines nor the bandwidth to the	vncviewers can keep  up	 these
	      rapid  screen changes: everything	will bog down when dragging or
	      scrolling.  So a scheme has to be	used to	 "eat"	much  of  that
	      pointer  input  before  re-polling  the  screen  and sending out
	      framebuffer updates. The mode number n can be 0 to 4 and selects
	      one of the schemes desribed below.

	      Note  that the -wireframe	and -scrollcopyrect__mode_s complement
	      -pointer_mode by detecting (and improving)  certain  periods  of
	      "rapid screen change".

	      n=0:  does  the same as -nodragging. (all	screen polling is sus-
	      pended if	a mouse	button is pressed.)

	      n=1: was the original scheme used	to about Jan  2004:  it	 basi-
	      cally  just  skips -input_skip keyboard or pointer events	before
	      repolling	the screen.

	      n=2 is an	improved scheme: by watching the current rate of input
	      events  it  tries	to detect if it	should try to "eat" additional
	      pointer events before continuing.

	      n=3 is basically a dynamic -nodragging mode: it detects when the
	      mouse motion has paused and then refreshes the display.

	      n=4  attempts  to	 measures network rates	and latency, the video
	      card read	rate, and how many tiles  have	been  changed  on  the
	      screen.	From  this,  it	 aggressively  tries  to  push	screen
	      "frames" when it decides it has enough resources to do so.   NOT

	      The  default  n  is  2.  Note  that modes	2, 3, 4	will skip -in-
	      put_skip keyboard	events (but it will not	count pointer events).
	      Also  note  that	these modes are	not available in -threads mode
	      which has	its own	pointer	event handling mechanism.

	      To try out the different pointer modes to	see  which  one	 gives
	      the  best	 response  for your usage, it is convenient to use the
	      remote control function, for example "x11vnc  -R	pm:4"  or  the
	      tcl/tk gui (Tuning -> pointer_mode -> n).

       -input_skip n

	      For  the	pointer	handling when non-threaded: try	to read	n user
	      input events before scanning display. n <	 0  means  to  act  as
	      though there is always user input.  Default: 10


	      Have  x11vnc  read and process all available client input	before


	      Similar to -allinput but use the	handleEventsEagerly  mechanism
	      built into LibVNCServer.


	      Enable  support  for  per-client input devices. Each client will
	      get its own cursor and keyboard focus.

       -speeds rd,bw,lat

	      x11vnc tries to estimate some speed parameters that are used  to
	      optimize	scheduling (e.g. -pointer_mode 4, -wireframe, -scroll-
	      copyrect)	and other things.  Use the -speeds option to set these
	      manually.	  The  triple  rd,bw,lat corresponds to	video h/w read
	      rate in MB/sec, network bandwidth	to clients in KB/sec, and net-
	      work  latency  to	 clients  in milliseconds, respectively.  If a
	      value is left blank, e.g.	"-speeds ,100,15", then	 the  internal
	      scheme is	used to	estimate the empty value(s).

	      Typical  PC  video cards have read rates of 5-10 MB/sec.	If the
	      framebuffer is in	main memory instead of video h/w (e.g. SunRay,
	      shadowfb,	dummy driver, Xvfb), the read rate may be much faster.
	      "x11perf -getimage500" can be used to get	a lower	bound  (remem-
	      ber to factor in the bytes per pixel).  It is up to you to esti-
	      mate the network bandwith	and latency to clients.	 For  the  la-
	      tency the	ping(1)	command	can be used.

	      For  convenience	there are some aliases provided, e.g. "-speeds
	      modem".	The  aliases  are:  "modem"  for  6,4,200;  "dsl"  for
	      6,100,50;	and "lan" for 6,5000,1

       -wmdt string

	      For  some	 features, e.g.	-wireframe and -scrollcopyrect,	x11vnc
	      has to work around issues	for certain window managers  or	 desk-
	      tops  (currently	kde  and  xfce).  By default it	tries to guess
	      which one, but it	can guess incorrectly.	Use this option	to in-
	      dicate  which  wm/dt.   string  can  be  "gnome",	 "kde",	"cde",
	      "xfce", or "root"	(classic X wm).	 Anything else is  interpreted
	      as "root".


	      Print debugging output for every pointer event.


	      Print debugging output for every keyboard	event.

       Same as -dp and -dk, respectively.  Use multiple	times for more output.

       -defer time

	      Time in ms to delay sending updates to connected clients (defer-
	      UpdateTime)  Default: 20

       -wait time

	      Time in ms to pause between screen polls.	 Used to cut  down  on
	      load.  Default: 20

       -extra_fbur n

	      Perform  extra  FrameBufferUpdateRequests	checks to try to be in
	      better sync with the client's requests.  What this does is  per-
	      form  extra polls	of the client socket at	critical times (before
	      '-defer' and '-wait' calls.)  The	default	 is  n=1.   Set	 to  a
	      larger number to insert more checks or set to n=0	to disable.  A
	      downside of these	extra calls is that more mouse	input  may  be
	      processed	than desired.

       -wait_ui	factor

	      Factor  by  which	to cut the -wait time if there has been	recent
	      user input (pointer or keyboard).	 Improves  response,  but  in-
	      creases  the  load  whenever you are moving the mouse or typing.
	      Default: 2.00

       -setdefer n

	      When the -wait_ui	mechanism cuts down the	wait time ms, set  the
	      defer  time  to  the same	ms value. n=1 to enable, 0 to disable,
	      and -1 to	set defer to 0 (no delay).  Similarly, 2 and -2	 indi-
	      cate  'urgent_update'  mode  should  be used to push the updates
	      even sooner.  Default: 1


	      Do not detect if the screen polling is "bogging down" and	 sleep
	      more.  Some activities with no user input	can slow things	down a
	      lot: consider a large terminal window with a long	build  running
	      in  it  continuously  streaming  text output.  By	default	x11vnc
	      will try to detect this (3 screen	polls in  a  row  each	longer
	      than  0.25  sec with no user input), and sleep up	to 1.5 secs to
	      let things "catch	up".  Use this option to disable  that	detec-

       -slow_fb	time

	      Floating point time in seconds to	delay all screen polling.  For
	      special purpose usage where a low	frame rate is  acceptable  and
	      desirable,  but  you want	the user input processed at the	normal
	      rate so you cannot use -wait.

       -xrefresh time

	      Floating point time in seconds to	indicate how often to  do  the
	      equivalent  of xrefresh(1) to force all windows (in the viewable
	      area if -id, -sid, or -clip is used) to repaint themselves.  Use
	      this only	if applications	misbehave by not repainting themselves
	      properly.	 See also -noxdamage.

       -nap, -nonap

	      Monitor activity and if it  is  low  take	 longer	 naps  between
	      screen  polls  to	really cut down	load when idle.	 Default: take

       -sb time

	      Time in seconds after NO activity	(e.g. screen blank) to	really
	      throttle	down the screen	polls (i.e. sleep for about 1.5	secs).
	      Use 0 to disable.	 Default: 60 Set the env. var.	X11VNC_SB_FAC-
	      TOR to scale it.

       -readtimeout n

	      Set  LibVNCServer	 rfbMaxClientWait  to n	seconds. On slow links
	      that take	a long time to paint the first screen LibVNCServer may
	      hit the timeout and drop the connection.	Default: 20 seconds.

       -ping n

	      Send  a  1x1  framebuffer	 update	to all clients every n seconds
	      (e.g. to try to keep a network connection	alive)

       -nofbpm,	-fbpm

	      If the system supports the FBPM (Frame Buffer Power  Management)
	      extension	 (i.e.	some  Sun systems), then prevent the video h/w
	      from going into a	reduced	power state when VNC clients are  con-

	      FBPM  capable video h/w save energy when the workstation is idle
	      by going into low	power states (similar to DPMS  for  monitors).
	      This interferes with x11vnc's polling of the framebuffer data.

	      "-nofbpm"	 means	prevent	 FBPM  low  power  states whenever VNC
	      clients are connected, while "-fbpm" means to  not  monitor  the
	      FBPM  state at all.  See the xset(1) manpage for details.	 -nof-
	      bpm is basically the same	as running "xset fbpm force on"	 peri-
	      odically.	 Default: -fbpm

       -nodpms,	-dpms

	      If  the  system supports the DPMS	(Display Power Management Sig-
	      naling) extension, then prevent the monitor from	going  into  a
	      reduced power state when VNC clients are connected.

	      DPMS  reduced power monitor states are a good thing and you nor-
	      mally want the power down	to take	place (usually x11vnc  has  no
	      problem exporting	the display in this state).  You probably only
	      want to use "-nodpms" to work around problems with Screen	Savers
	      kicking  on  in  DPMS  low power states.	There is known problem
	      with kdesktop_lock on KDE	where the screen saver	keeps  kicking
	      in  every	time user input	stops for a second or two.  Specifying
	      "-nodpms"	works around it.

	      "-nodpms"	means prevent  DPMS  low  power	 states	 whenever  VNC
	      clients  are  connected,	while "-dpms" means to not monitor the
	      DPMS state  at  all.   See  the  xset(1)	manpage	 for  details.
	      -nodpms  is  basically  the same as running "xset	dpms force on"
	      periodically.  Default: -dpms


	      If the system supports the DPMS (Display Power  Management  Sig-
	      naling) extension, then try to keep the monitor in a powered off
	      state.  This is to prevent nosey people at the physical  display
	      from  viewing what is on the screen.  Be sure to lock the	screen
	      before disconnecting.

	      This method is far from bullet proof, e.g. suppose  someone  at-
	      taches a non-DPMS	monitor, or loads the machine so that there is
	      a	gap of time before x11vnc restores the powered off state?   On
	      many  machines  if he floods it with keyboard and	mouse input he
	      can see flashes of what is on the	screen	before	the  DPMS  off
	      state  is	 reestablished.	 For this to work securely there would
	      need to be support in the	X server to  do	 this  exactly	rather
	      than approximately with DPMS.


	      As -forcedpms but	only when VNC clients are connected.


	      The  UltraVNC  ServerInput  extension is supported.  This	allows
	      the VNC viewer to	click a	button	that  will  cause  the	server
	      (x11vnc) to try to disable keyboard and mouse input at the phys-
	      ical display and put the monitor in dpms powered off state.  Use
	      this option to skip powering off the monitor.


	      Disable  the  following  UltraVNC	 extensions:  SingleWindow and
	      ServerInput.  The	others managed by LibVNCServer (textchat,  1/n
	      scaling, rfbEncodingUltra) are not.


	      Place  a	local  UltraVNC	 chat  window  on the X11 display that
	      x11vnc is	polling.  That way the person on the  VNC  viewer-side
	      can  chat	 with  the  person  at the physical X11	console. (e.g.
	      helpdesk w/o telephone)

	      For this to work the SSVNC package  (version  1.0.21  or	later)
	      MUST  BE	installed  on  the  system  where  x11vnc runs and the
	      'ssvnc' command must be available	in $PATH.  The ssvncviewer  is
	      used   as	  a   chat   window   helper.	 See  http://www.karl-

	      This option implies '-rfbversion 3.6' so as  to  trick  UltraVNC
	      viewers,	otherwise they assume chat is not available.  To spec-
	      ify a different rfbversion, place	it after the  -chatwindow  op-
	      tion on the cmdline.

	      See  also	 the  remote  control  'chaton'	and 'chatoff' actions.
	      These can	also be	set from the tkx11vnc GUI.


	      Do not use the X DAMAGE extension	to detect framebuffer  changes
	      even  if	it  is	available.  Use	-xdamage if your default is to
	      have it off.

	      x11vnc's use of the DAMAGE extension: 1)	significantly  reduces
	      the  load	 when  the screen is not changing much,	and 2) detects
	      changed areas (small ones	by default) more quickly.

	      Currently	the DAMAGE extension is	overly conservative and	 often
	      reports large areas (e.g.	a whole	terminal or browser window) as
	      damaged even though the actual changed region  is	 much  smaller
	      (sometimes just a	few pixels).  So heuristics were introduced to
	      skip large areas and use the damage rectangles only  as  "hints"
	      for  the traditional scanline polling.  The following tuning pa-
	      rameters are introduced to adjust	this behavior:

       -xd_area	A

	      Set the largest DAMAGE rectangle area  A	(in  pixels:  width  *
	      height)  to trust	as truly damaged: the rectangle	will be	copied
	      from the framebuffer (slow) no matter  what.   Set  to  zero  to
	      trust *all* rectangles. Default: 20000

       -xd_mem f

	      Set  how	long  DAMAGE rectangles	should be "remembered",	f is a
	      floating point number and	is in units of the scanline repeat cy-
	      cle  time	 (32  iterations).   The  default (1.0)	should give no
	      painting problems. Increase it if	there are problems or decrease
	      it to live on the	edge (perhaps useful on	a slow machine).

       -sigpipe	string

	      Broken  pipe  (SIGPIPE)  handling.   string  can	be "ignore" or
	      "exit".  For "ignore" LibVNCServer will handle the  abrupt  loss
	      of  a  client  and  continue, for	"exit" x11vnc will cleanup and
	      exit at the 1st broken connection.

	      This option is not really	needed since LibVNCServer is doing the
	      correct thing now	for quite some time.  However, for convenience
	      you can use it to	 ignore	 other	signals,  e.g.	"-sigpipe  ig-
	      nore:HUP,INT,TERM" in case that would be useful for some sort of
	      application.  You	can also put "exit:.." in  the	list  to  have
	      x11vnc  cleanup  on  the	listed signals.	"-sig" is an alias for
	      this option if you don't like  the  'pipe'.  Example:  -sig  ig-

       -threads, -nothreads

	      Whether  or  not to use the threaded LibVNCServer	algorithm [rf-
	      bRunEventLoop] if	libpthread is available.   In  this  mode  new
	      threads (one for input and one for output) are created to	handle
	      each new client.	Default: -nothreads.

	      Thread stability is much improved	in version 0.9.8.

	      Multiple clients in threaded mode	should be stable for the  ZRLE
	      encoding	on  all	 platforms.   The Tight	and Zlib encodings are
	      currently	only stable on Linux for  multiple  clients.   Compile
	      with  -DTLS=__thread  if your OS and compiler and	linker support

	      For resizes (randr, etc.)	set this env. var. to  the  number  of
	      milliseconds  to	sleep:	X11VNC_THREADS_NEW_FB_SLEEP at various
	      places in	the do_new_fb()	action.	 This is to let	various	activ-
	      ities settle.  Default is	about 500ms.

	      Multiple clients in threaded mode	could yield better performance
	      for 'class-room' broadcasting usage; also	in -appshare broadcast
	      mode.  See also the -reflect option.

       -fs f

	      If  the  fraction	 of changed tiles in a poll is greater than f,
	      the whole	screen is updated.  Default: 0.75

       -gaps n

	      Heuristic	to fill	in gaps	in rows	or cols	of n  or  less	tiles.
	      Used to improve text paging.  Default: 4

       -grow n

	      Heuristic	 to grow islands of changed tiles n or wider by	check-
	      ing the tile near	the boundary.  Default:	3

       -fuzz n

	      Tolerance	in pixels to mark a tiles edges	as changed.   Default:


	      Print debugging output for tiles,	fb updates, etc.


	      Instead  of  polling the X display framebuffer (fb) for changes,
	      periodically copy	all of X display fb into main memory and exam-
	      ine that copy for	changes.  (This	setting	also applies for non-X
	      -rawfb modes).  Under some circumstances this will  improve  in-
	      teractive	 response,  or at least	make things look smoother, but
	      in others	(most!)	it will	make the response worse.  If the video
	      h/w  fb  is such that reading small tiles	is very	slow this mode
	      could help.  To keep the "framerate" up the screen  size	x  bpp
	      cannot  be  too  large.  Note that this mode is very wasteful of
	      memory I/O resources (it makes full screen copies	even if	 noth-
	      ing  changes).   It may be of use	in video capture-like applica-
	      tions, webcams, or where window tearing is a problem.

       -rawfb string

	      Instead of polling  X,  poll  the	 memory	 object	 specified  in

	      For   file   polling,   to   memory  map	mmap(2)	 a  file  use:
	      "map:/path/to/a/file@WxHxB", with	framebuffer Width, Height, and
	      Bits per pixel.  "mmap:..." is the same.

	      If  there	 is  trouble  with  mmap,  use "file:/..."  for	slower
	      lseek(2) based reading.

	      Use "snap:..." to	imply -snapfb  mode  and  the  "file:"	access
	      (this  is	for unseekable devices that only provide the fb	all at
	      once, e.g. a video camera	provides the whole frame).

	      For shared memory	segments string	is of the form:	 "shm:N@WxHxB"
	      which specifies a	shmid N	and with WxHxB as above.  See shmat(1)
	      and ipcs(1)

	      If you do	not supply a type "map"	is assumed if the file	exists
	      (see the next paragraphs for some	exceptions to this.)

	      If  string is "setup:cmd", then the command "cmd"	is run and the
	      first line from it is read and used as string.  This allows ini-
	      tializing	 the  device,  determining WxHxB, etc. These are often
	      done as root so take care.

	      If the string begins with	"video", see the  VIDEO4LINUX  discus-
	      sion  below  where  the  device may be queried for (and possibly
	      set) the framebuffer parameters.

	      If the string begins with	"console", "/dev/fb", "fb",  or	 "vt",
	      see the LINUX CONSOLE discussion below where the framebuffer de-
	      vice is opened and keystrokes (and possibly  mouse  events)  are
	      inserted into the	console.

	      If the string begins with	"vnc", see the VNC HOST	discussion be-
	      low where	the framebuffer	is taken as that of another remote VNC

	      Optional	suffixes  are ":R/G/B" and "+O"	to specify red,	green,
	      and blue masks (in hex) and an offset into  the  memory  object.
	      If  the  masks are not provided x11vnc guesses them based	on the
	      bpp (if the colors look wrong, you need to provide the masks.)

	      Another optional suffix is the Bytes  Per	 Line  which  in  some
	      cases   is   not	 WxB/8.	   Specify   it	  as   WxHxB-BPL  e.g.
	      800x600x16-2048.	This could be a	normal width 1024 at 16bpp fb,
	      but only width 800 shows up.

	      So the full format is: mode:file@WxHxB:R/G/B+O-BPL


	      -rawfb shm:210337933@800x600x32:ff/ff00/ff0000

	      -rawfb map:/dev/fb0@1024x768x32

	      -rawfb map:/tmp/Xvfb_screen0@640x480x8+3232

	      -rawfb file:/tmp/my.pnm@250x200x24+37

	      -rawfb		 file:/dev/urandom@128x128x8		-rawfb
	      snap:/dev/video0@320x240x24 -24to32 -rawfb video0	 -rawfb	 video
	      -pipeinput VID -rawfb console -rawfb vt2 -rawfb vnc:somehost:0

	      (see ipcs(1) and fbset(1)	for the	first two examples)

	      In  general  all	user  input  is	 discarded by default (see the
	      -pipeinput option	for how	to use a helper	 program  to  insert).
	      Most  of	the  X11 (screen, keyboard, mouse) options do not make
	      sense and	many will cause	this mode to crash,  so	 please	 think
	      twice before setting or changing them in a running x11vnc.

	      If  you DO NOT want x11vnc to close the X	DISPLAY	in rawfb mode,
	      prepend a	"+" e.g. +file:/dev/fb0...  Keeping the	 display  open
	      enables  the default remote-control channel, which could be use-
	      ful.  Alternatively, if you specify -noviewonly, then the	 mouse
	      and  keyboard  input are STILL sent to the X display, this usage
	      should be	very rare, i.e.	doing something	strange	with /dev/fb0.

	      If the device is not "seekable" (e.g. webcam) try	reading	it all
	      at  once in full snaps via the "snap:" mode (note: this is a re-
	      source hog).  If you are using file:  or	map:  AND  the	device
	      needs  to	be reopened for	*every*	snapfb snapshot, set the envi-
	      ronment variable:	SNAPFB_RAWFB_RESET=1 as	well.

	      If you want x11vnc to dynamically	transform  a  24bpp  rawfb  to
	      32bpp  (note  that  this will be slower) also supply the -24to32
	      option.  This would be useful for, say, a	video camera that  de-
	      livers  the pixel	data as	24bpp packed RGB.  This	is the default
	      under "video" mode if the	bpp is 24.

	      Normally the bits	per pixel, B, is 8, 16,	or 32 (or rarely  24),
	      however  there is	also some support for B	< 8 (e.g. old graphics
	      displays 4 bpp or	1 bpp).	 In this case you certainly must  sup-
	      ply  the	masks as well: WxHxB:R/G/B.  The pixels	will be	padded
	      out to 8 bpp using depth 8 truecolor.  The scheme	currently does
	      not  work	with snap fb (ask if interested.) B=1 monochrome exam-
	      ple: file:/dev/urandom@128x128x1:1/1/1 Some other	like this  are
	      128x128x2:3/3/3 128x128x4:7/7/7

	      For B < 8	framebuffers you can also set the env. var RAWFB_CGA=1
	      to try a CGA mapping for B=4 (e.g. linux vga16fb driver.)	  Note
	      with  low	bpp and/or resolution VGA and VGA16 modes on the Linux
	      console one's attempt to export them via	x11vnc	can  often  be
	      thwarted due to special color palettes, pixel packings, and even
	      video painting buffering.	 OTOH, often  experimenting  with  the
	      RGB masks	can yield something recognizable.

	      VIDEO4LINUX:  on	Linux some attempt is made to handle video de-
	      vices (webcams or	TV tuners) automatically.  The idea is the Wx-
	      HxB  will	be extracted from the device itself.  So if you	do not
	      supply "@WxHxB...	 parameters x11vnc will	try to determine them.
	      It first tries the v4l API if that support has been compiled in.
	      Otherwise	it will	run the	v4l- info(1) external program if it is

	      The  simplest  examples  are  "-rawfb video" and "-rawfb video1"
	      which imply the device file /dev/video and /dev/video1,  respec-
	      tively.	You can	also supply the	/dev if	you like, e.g. "-rawfb

	      Since the	video capture device framebuffer usually changes  con-
	      tinuously	 (e.g.	brightness  fluctuations), you may want	to use
	      the -wait, -slow_fb, or -defer options to	lower the  "framerate"
	      to cut down on network VNC traffic.

	      A	more sophisticated video device	scheme allows initializing the
	      device's settings	using:

	      -rawfb video:<settings>

	      The prefix could also be,	as above, e.g.	"video1:"  to  specify
	      the  device  file.   The	v4l  API must be available for this to
	      work.  Otherwise,	you will need to try to	initialize the	device
	      with  an	external  program, e.g.	xawtv, spcaview, and hope they
	      persist when x11vnc re-opens the device.

	      <settings> is a comma separated list of  key=value  pairs.   The
	      device's brightness, color, contrast, and	hue can	be set to per-
	      centages,	e.g. br=80,co=50,cn=44,hu=60.

	      The device filename can be set too if needed  (if	 it  does  not
	      start with "video"), e.g.	fn=/dev/qcam.

	      The  width,  height  and	bpp of the framebuffer can be set via,
	      e.g., w=160,h=120,bpp=16.

	      Related to the bpp above,	the pixel format can be	 set  via  the
	      fmt=XXX,	where  XXX can be one of: GREY,	HI240, RGB555, RGB565,
	      RGB24, and RGB32 (with bpp 8, 8, 16,  16,	 24,  and  32  respec-
	      tively).	See for more info (V4L api).

	      For  TV/rf  tuner	 cards one can set the tuning mode via tun=XXX
	      where XXX	can be one of PAL, NTSC, SECAM,	or AUTO.

	      One can switch the input channel by the inp=XXX  setting,	 where
	      XXX is the name of the input channel (Television,	Composite1, S-
	      Video, etc).  Use	the name that is in the	information about  the
	      device that is printed at	startup.

	      For  input channels with tuners (e.g. Television)	one can	change
	      which station is selected	by the sta=XXX setting.	  XXX  is  the
	      station  number.	 Currently  only  the ntsc-cable-us (US	cable)
	      channels are built into x11vnc.  See the -freqtab	 option	 below
	      to supply	one from xawtv.	If XXX is greater than 500, then it is
	      interpreted as a raw frequency in	KHz.


	      -rawfb video:br=80,w=320,h=240,fmt=RGB32,tun=NTSC,sta=47

	      one might	need to	add inp=Television too for the	input  channel
	      to be TV if the card doesn't come	up by default in that one.

	      Note  that not all video capture devices will support all	of the
	      above settings.

	      See the -pipeinput VID option below for a	 way  to  control  the
	      settings	through	the VNC	Viewer via keystrokes.	As a shortcut,
	      if  the  string  begins  "Video.."  instead  of  "video.."  then
	      -pipeinput VID is	implied.

	      As  above,  if  you  specify  a "@WxHxB..." after	the <settings>
	      string they are used verbatim: the device	is not queried for the
	      current values.  Otherwise the device will be queried.

	      LINUX  CONSOLE:	The  following describes some ways to view and
	      possibly interact	with the Linux text/graphics console (i.e. not
	      X11 XFree86/Xorg)

	      Note: If the LibVNCServer	LinuxVNC program is on your system you
	      may want to use that instead of the following method because  it
	      will  be faster and more accurate	for the	Linux text console and
	      includes mouse support.  There is, however, the  basic  LinuxVNC
	      functionality  in	 x11vnc	 if you	replace	"console" with "vt" in
	      the examples below.

	      If the rawfb string begins with "console"	the framebuffer	device
	      /dev/fb0	is  opened and /dev/tty0 is opened too.	 The latter is
	      used to inject keystrokes	(not all are supported,	but the	 basic
	      ones  are).   You	will need to be	root to	inject keystrokes, but
	      not necessarily to open /dev/fb0.	 /dev/tty0 refers to  the  ac-
	      tive  VT,	 to indicate one explicitly, use, e.g.,	"console2" for
	      /dev/tty2, etc. by indicating the	specific VT number.

	      For the Linux framebuffer	device,	/dev/fb0, (fb1,	etc) to	be en-
	      abled  the  appropriate  kernel  drivers	must  be loaded.  E.g.
	      vesafb or	 vga16fb  and  also  by	 setting  the  boot  parameter
	      vga=0x301	 (or  0x314,  0x317, etc.)  (The vga=... method	is the
	      preferred	way; set your machines up that way.)  Otherwise	 there
	      will  be	a  'No	such device' error.  You can also load a Linux
	      framebuffer driver specific to your make of video	card for  more
	      functionality.   Once  the machine is booted one can often 'mod-
	      probe' the fb driver as root to obtain a framebuffer device.

	      If you cannot get	/dev/fb0 working on Linux, try using the  Lin-
	      uxVNC  emulation	mode by	"-rawfb	vtN" where N = 1, ... 6	is the
	      Linux Virtual Terminal (aka virtual console) you wish  to	 view,
	      e.g.  "-rawfb vt2".  Unlike /dev/fb mode,	it need	not be the ac-
	      tive Virtual Terminal.  Note that	this mode can only  show  text
	      and not graphics.	 x11vnc	polls the text in /dev/vcsaN

	      Set the env. var.	RAWFB_VCSA_BW=1	to disable colors in the "vtN"
	      mode (i.e. black and white only.)	 If you	do not prefer the  de-
	      fault 16bpp set RAWFB_VCSA_BPP to	8 or 32.  If you need to tweak
	      the rawfb	parameters by using the	'console_guess'	string printed
	      at startup, be sure to indicate the snap:	method.

	      uinput:  If the Linux version appears to be 2.6 or later and the
	      "uinput" module appears to be present  (modprobe	uinput),  then
	      the uinput method	will be	used instead of	/dev/ttyN.  uinput al-
	      lows insertion of	BOTH keystrokes	and mouse input	and so it pre-
	      ferred when accessing graphical (e.g. QT-embedded) linux console
	      apps.  It	also provides more accurate keystroke insertion.   See
	      -pipeinput  UINPUT  below	for more information on	this mode; you
	      will have	to use -pipeinput if you want to tweak any UINPUT  pa-
	      rameters.	  You  may  also  want to also use the -nodragging and
	      -cursor none options.  Use "console0", etc  or  -pipeinput  CON-
	      SOLE to force the	/dev/ttyN method.

	      Note you can change the Linux VT remotely	using the chvt(1) com-
	      mand to make the one you want be the active one (e.g. 'chvt 3').
	      Sometimes	 switching  out	 and  back  corrects the framebuffer's
	      graphics state.  For the "-rawfb vtN" mode there is no  need  to
	      switch the VT's.

	      To skip input injecting entirely use "consolex" or "vtx".

	      The  string  "/dev/fb0"  (1,  etc.) can be used instead of "con-
	      sole".  This can be used to specify a different framebuffer  de-
	      vice,  e.g. /dev/fb1.  As	a shortcut the "/dev/" can be dropped.
	      If the name is something nonstandard, use	"console:/dev/foofb"

	      If you do	not want x11vnc	to guess the framebuffer's  WxHxB  and
	      masks automatically (sometimes the kernel	gives incorrect	infor-
	      mation), specify them with a @WxHxB (and optional	:R/G/B	masks)
	      at the end of the	string.

	      Examples:	-rawfb console -rawfb /dev/fb0		 (same)	-rawfb
	      console3		    (force    /dev/tty3)    -rawfb    consolex
	      (no  keystrokes or mouse)	-rawfb console:/dev/nonstd -rawfb con-
	      sole	-pipeinput	UINPUT:accel=4.0      -rawfb	   vt3
	      (/dev/tty3 w/o /dev/fb0)

	      VNC  HOST: if the	-rawfb string is of the	form "vnc:host:N" then
	      the VNC display "N" on the remote	VNC server "host" is connected
	      to  (i.e.	 x11vnc	 acts  as a VNC	client itself) and that	frame-
	      buffer is	exported.

	      This mode	is really only of use if you  are  trying  to  improve
	      performance  in  the  case  of many (e.g.	> 10) simultaneous VNC
	      viewers, and you try a divide and	conquer	scheme to reduce band-
	      width  and improve responsiveness.  (However, another user found
	      this mode	useful to export a demo	display	through	a  slow	 link:
	      then multiple demo viewers connected to the reflecting x11vnc on
	      the fast side of the link, and so	avoided	all of the demo	 view-
	      ers going	through	the slow link.)

	      For  example,  if	there will be 64 simultaneous VNC viewers this
	      can lead to a lot	of redundant  VNC  traffic  to	and  from  the
	      server  host:N, extra CPU	usage, and all viewers response	can be
	      reduced by having	to wait	for writes to the  slowest  client  to
	      finish.	However,  if you set up	8 reflectors/repeaters started
	      with option -rawfb vnc:host:N, then there	are only 8 connections
	      to  host:N.  Each	repeater then handles 8	vnc viewer connections
	      thereby spreading	the load around.  In classroom	broadcast  us-
	      age,  try	to put the repeaters on	different switches.  This mode
	      is the same as -reflect host:N.  Replace "host:N"	by "listen" or
	      "listen:port" for	a reverse connection.

	      Overall  performance will	not be as good as a single direct con-
	      nection because, among other  things,  there  is	an  additional
	      level of framebuffer polling and pointer motion can still	induce
	      many changes per second that must	be propagated.	 Tip:  if  the
	      remote  VNC  is  x11vnc  doing wireframing, or an	X display that
	      does wireframing that gives much	better	response  than	opaque
	      window dragging.	Consider the -nodragging option	if the problem
	      is severe.

	      The env. var. X11VNC_REFLECT_PASSWORD can	be set to the password
	      needed	to   log   into	  the	vnc   host   server,   or   to
	      "file:path_to_file" to indicate a	file containing	 the  password
	      as its first line.

	      To set the pixel format that x11vnc requests as a	VNC CLIENT set
	      the env. vars: X11VNC_REFLECT_bitsPerSample  X11VNC_REFLECT_sam-
	      plesPerPixel, and	X11VNC_REFLECT_bytesPerPixel; the defaults are
	      8, 3, 4.	2, 3, 1	would give a low color mode.  See the function
	      rfbGetClient() in	libvncclient for more info.

	      The  VNC	HOST  mode implies -shared.  Use -noshared as a	subse-
	      quent cmdline option to disable sharing.

       -freqtab	file

	      For use with "-rawfb video" for TV tuner devices to specify sta-
	      tion  frequencies.   Instead of using the	built in ntsc-cable-us
	      mapping of station number	to frequency, use the  data  in	 file.
	      For  stations  that  are not numeric, e.g. SE20, they are	placed
	      above the	highest	numbered station in the	order they are	found.
	      Example:	"-freqtab /usr/X11R6/share/xawtv/europe-west.list" You
	      can make your own	freqtab	by copying the xawtv format.

       -pipeinput cmd

	      This option lets you supply an  external	command	 in  cmd  that
	      x11vnc  will  pipe  all  of the user input events	to in a	simple
	      format.  In -pipeinput mode by default x11vnc will  not  process
	      any  of the user input events.  If you prefix cmd	with "tee:" it
	      will both	send them to the pipe command and process them.	 For a
	      description  of  the  format run "-pipeinput tee:/bin/cat".  An-
	      other prefix is "reopen" which means to reopen pipe if it	exits.
	      Separate multiple	prefixes with commas.

	      In  combination  with  -rawfb  one  might	 be able to do amusing
	      things (e.g. control non-X devices).   To	 facilitate  this,  if
	      -rawfb is	in effect then the value is stored in X11VNC_RAWFB_STR
	      for the pipe command to use if it	wants. Do 'env | grep  X11VNC'
	      for more.

	      Built-in pipeinput modes (no external program required):

	      If cmd is	"VID" and you are using	the -rawfb for a video capture
	      device, then an internal list of keyboard	mappings  is  used  to
	      set parameters of	the video.  The	mappings are:

	      "B"  and "b" adjust the brightness up and	down.  "H" and "h" ad-
	      just the hue.  "C" and "c" adjust	the colour.  "N" and  "n"  ad-
	      just  the	 contrast.  "S"	and "s"	adjust the size	of the capture
	      screen.  "I" and "i" cycle through input channels.  Up and  Down
	      arrows  adjust  the  station  (if	 a tuner) F1, F2, ..., F6 will
	      switch the video capture pixel format to HI240,  RGB565,	RGB24,
	      RGB32,  RGB555, and GREY respectively.  See -rawfb video for de-

	      If cmd is	"CONSOLE" or "CONSOLEn"	where n	 is  a	Linux  console
	      number,  then the	linux console keystroke	insertion to /dev/ttyN
	      (see -rawfb console) is performed.

	      If cmd begins with "UINPUT" then the Linux uinput	module is used
	      to  insert  both keystroke and mouse events to the Linux console
	      (see -rawfb above).  This	usually	is the	/dev/input/uinput  de-
	      vice file	(you may need to create	it with	"mknod /dev/input/uin-
	      put c 10 223" and	insert the module with "modprobe uinput".

	      The UINPUT mode currently	only does US keyboards	(a  scan  code
	      option may be added), and	not all	keysyms	are supported.	But it
	      is probably more accurate	than the "CONSOLE" method.

	      You may want to use the options -cursor none and -nodragging  in
	      this mode.

	      Additional   tuning   options   may   be	 supplied   via:  UIN-
	      PUT:opt1,opt2,...	(a comma separated list). If an	option	begins
	      with "/" it is taken as the uinput device	file.

	      Which  uinput  is	injected can be	controlled by an option	string
	      made of the characters "K", "M", and "B"	(see  the  -input  op-
	      tion),  e.g.  "KM"  allows  keystroke  and motion	but not	button

	      A	UINPUT option of the form: accel=f, or	accel=fx+fy  sets  the
	      mouse  motion "acceleration".  This is used to correct raw mouse
	      relative motion into  how	 much  the  application	 cursor	 moves
	      (x11vnc  has  no control over, or	knowledge of how the windowing
	      application interprets the raw mouse  motions).	Typically  the
	      acceleration  for	 an X display is 2 (see	xset "m" option).  "f"
	      is a floating point number, e.g. 3.0.  Use "fx+fy" if  you  need
	      to supply	different corrections for x and	y.

	      Note:  the default acceleration is 2.0 since it seems both X and
	      qt-embedded often	(but not always) use this value.

	      Even with	a correct accel	setting	the mouse  position  will  get
	      out  of  sync (probably due to a mouse "threshold" setting where
	      the acceleration doe not apply, set xset(1) ).  The  option  re-
	      set=N sets the number of ms (default 150)	after which the	cursor
	      is attempted to be reset (by forcing the mouse  to  (0,  0)  via
	      small  increments	 and  then back	out to (x, y) in 1 jump), This
	      correction seems to be needed but	can cause jerkiness  or	 unex-
	      pected behavior with menus, etc.	Use reset=0 to disable.

	      If  you  set  the	 env.  var  X11VNC_UINPUT_THRESHOLDS  then the
	      thresh=n mode will be enabled.   It  is  currently  not  working
	      well.   If  |dx|	<= thresh and |dy| < thresh no acceleration is
	      applied.	Use "thresh=+n"	|dx| + |dy| < thresh to	 be  used  in-
	      stead (X11?)

	      Example: -pipeinput UINPUT:accel=4.0 -cursor none

	      If  the  uinput  device has an absolute pointer (as opposed to a
	      normal mouse that	is a relative pointer) you can specify the op-
	      tion "abs".  Note	that a touchpad	on a laptop is an absolute de-
	      vice to some degree.  This (usually)  avoids  all	 the  problems
	      with  mouse  acceleration.   If  x11vnc has trouble deducing the
	      size of the device, use "abs=WxH".  Furthermore, if  the	device
	      is  a  touchscreen  (assumed  to	have  an absolute pointer) use
	      "touch" or "touch=WxH".  For touchscreens, when a	 mouse	button
	      is pressed, a pressure increase is injected, and when the	button
	      is released a pressure of	zero is	injected.

	      If touch has been	set, use "touch_always=1" to indicate whenever
	      the  mouse  moves	 with no button	pressed, a touch event of zero
	      pressure should be sent anyway.  Also use	"btn_touch=1" to indi-
	      cate  a  BTN_TOUCH keystroke press or release should be sent in-
	      stead of a pressure change.  Set "dragskip=n" to skip n  dragged
	      mouse  touches (with pressure applied) before injecting one.  To
	      indicate the pressure that should	be sent	when there is a	button
	      click  for  a  touchscreen device, specify pressure=n, e.g. n=5.
	      The default is n=1.

	      If a touch screen	is being used ("touch" above) and it is	having
	      its input	processed by tslib, you	can specify the	tslib calibra-
	      tion    file     via     tslib_cal=<file>.      For     example,
	      tslib_cal=/etc/pointercal.  To get accurate or even usable posi-
	      tioning this is required when tslib is in	use.

	      The Linux	uinput mechanism can be	bypassed and one can write in-
	      put events DIRECTLY to the devices instead.  To do this, specify
	      one or  more  of	the  following	for  the  input	 classes:  di-
	      rect_rel=<device>	direct_abs=<device> direct_btn=<device>	or di-
	      rect_key=<device>.  The <device> file is usually something  like
	      /dev/input/event1	 but  you can specify any device file or pipe.
	      You must specify each one	of the above classes even if they cor-
	      respond  to  the same device file	(rel/abs and btn are often the
	      same.)  Look at the file /proc/bus/input/devices to get an  idea
	      what  is available and the device	filenames.  Note: The /dev/in-
	      put/mouse* devices do not	seem to	work,  use  the	 corresponding
	      /dev/input/event*	 file  instead.	  Any input class not directly
	      specified	as above will be handled via the uinput	mechanism.  To
	      disable  creating	a uinput device	(and thereby discarding	unhan-
	      dled input), specify "nouinput".


	      -pipeinput UINPUT:direct_abs=/dev/input/event1

	      this was used on a qtmoko	Neo freerunner (armel):

	      -pipeinput      UINPUT:touch,tslib_cal=/etc/pointercal,	   di-

	      (where the long line has been split into two.)

	      You  can set the env. var	X11VNC_UINPUT_DEBUG=1 or higher	to get
	      debugging	output for UINPUT mode.


	      For the native MacOSX server, disable dimming.


	      For the native MacOSX server, disable display sleep.


	      For the native MacOSX server, disable screensaver.


	      For the native MacOSX server, do not wait	for the	user to	switch
	      back to his display.

       -macwheel n

	      For  the	native	MacOSX	server,	set the	mouse wheel speed to n
	      (default 5).


	      For the native MacOSX server, do not swap	mouse buttons 2	and 3.


	      For the native MacOSX server, do not resize or reset the	frame-
	      buffer  even  if	it  is	detected that the screen resolution or
	      depth has	changed.

       -maciconanim n

	      For the native MacOSX server, set	n to the number	 of  millisec-
	      onds  that  the  window  iconify/deiconify  animation takes.  In
	      -ncache mode this	value will be used to skip  the	 animation  if
	      possible.	(default 400)


	      For  the	native	MacOSX	server,	in -ncache client-side caching
	      mode, try	to cache pull down menus  (not	perfect	 because  they
	      have animated fades, etc.)


	      For  the native MacOSX server, use the original keystroke	inser-
	      tion code	based on a US keyboard.


	      For the native MacOSX server, do not use OpenGL for screen  cap-
	      ture,  but rather	use the	original, deprecated raw memory	access
	      method: addr = CGDisplayBaseAddress().


	      For the native MacOSX server, disable  the  raw  memory  address
	      screen capture method.

	      MACOSX  NOTE: There are some deprecated MacOSX interfaces	to in-
	      ject keyboard and	mouse events and the raw memory	access	method
	      is  deprecated  as  well	(however,  OpenGL will be preferred if
	      available	because	it is faster.)	One can	force  not  using  any
	      deprecated  interfaces  at  compile time by setting -DX11VNC_MA-
	      COSX_NO_DEPRECATED=1 in CPPFLAGS.	 Or to turn them  off  one  by
	      CATED_FRAMEBUFFER=1  At  run  time, for testing and workarounds,
	      one can disable  them  by	 using:	 -env  X11VNC_MACOSX_NO_DEPRE-
	      COSX_NO_DEPRECATED_FRAMEBUFFER=1	Note:  When  doing  either  of
	      these for	the mouse input	not everything works  currently,  e.g.
	      double  clicks  and  wireframing.	  Also,	 screen	resolution and
	      pixel depth changes will not be  automatically  detected	unless
	      the deprecated framebuffer interfaces are	allowed.

	      Conversely,  if  you are compiling on an older machine that does
	      not have some of the newer interfaces, you may need  to  specify
	      COSX_USE_GETMAINDEVICE to	regain the very	old QuickDraw GetMain-
	      Device() interface (rare...)

       -gui [gui-opts]

	      Start up a simple	tcl/tk gui based on the	remote control options
	      -remote/-query described below.  Requires	the "wish" program  to
	      be  installed  on	 the machine.  "gui-opts" is not required: the
	      default is to start up both the full gui and x11vnc with the gui
	      showing up on the	X display in the environment variable DISPLAY.

	      "gui-opts"  can  be  a comma separated list of items.  Currently
	      there are	these types of items: 1) a gui mode, a	2)  gui	 "sim-
	      plicity",	 3)  the  X  display  the  gui should display on, 4) a
	      "tray" or	"icon" mode, and 5) a gui geometry.

	      1) The gui mode can be "start", "conn", or "wait"	"start"	is the
	      default mode above and is	not required.  "conn" means do not au-
	      tomatically start	up x11vnc, but instead just try	to connect  to
	      an existing x11vnc process.  "wait" means	just start the gui and
	      nothing else (you	will later instruct the	gui to start x11vnc or
	      connect to an existing one.)

	      2)  The  gui simplicity is off by	default	(a power-user gui with
	      all options is presented)	To start with something	less  daunting
	      supply  the  string  "simple" ("ez" is an	alias for this).  Once
	      the gui is started you can toggle	between	the two	with "Misc  ->

	      3)  Note	the  possible  confusion regarding the potentially two
	      different	X displays: x11vnc polls one, but you may want the gui
	      to  appear on another.  For example, if you ssh in and x11vnc is
	      not running yet you may want the gui to come  back  to  you  via
	      your ssh redirected X display (e.g. localhost:10).

	      If  you  do  not	specify	a gui X	display	in "gui-opts" then the
	      DISPLAY environment variable and -display	option are  tried  (in
	      that order).  Regarding the x11vnc X display the gui will	try to
	      communication with, it first tries -display  and	then  DISPLAY.
	      For  example, "x11vnc -display :0	-gui otherhost:0", will	remote
	      control an x11vnc	polling	:0 and display the gui on  otherhost:0
	      The  "tray/icon" mode below reverses this	preference, preferring
	      to display on the	x11vnc display.

	      4) When "tray" or	"icon" is specified, the gui  presents	itself
	      as  a  small  icon  with	behavior typical of a "system tray" or
	      "dock applet".  The color	of the	icon  indicates	 status	 (con-
	      nected clients) and there	is also	a balloon status.  Clicking on
	      the icon gives a menu from which properties, etc,	can be set and
	      the  full	 gui is	available under	"Advanced".  To	be fully func-
	      tional, the gui mode should be "start" (the default).

	      Note that	tray or	icon mode will imply the -forever  x11vnc  op-
	      tion (if the x11vnc server is started along with the gui)	unless
	      -connect or -connect_or_exit has been specified.	So x11vnc (and
	      the  tray/icon  gui)  will  wait	for more connections after the
	      first client disconnects.	 If you	want only one  viewer  connec-
	      tion include the -once option.

	      For  "icon"  the gui just	a small	standalone window.  For	"tray"
	      it will attempt to embed itself in the "system tray"  if	possi-
	      ble. If "=setpass" is appended then at startup the X11 user will
	      be prompted to set the VNC session password.  If =<hexnumber> is
	      appended	that  icon  will attempt to embed itself in the	window
	      given by hexnumber.  Use =noadvanced to disable  the  full  gui.
	      (To supply more than one,	use "+"	sign).	E.g. -gui tray=setpass
	      and -gui icon=0x3600028

	      Other modes: "full", the default	and  need  not	be  specified.
	      "-gui none", do not show a gui, useful to	override a ~/.x11vncrc
	      setting, etc.

	      5) When "geom=+X+Y" is specified,	that geometry is passed	to the
	      gui  toplevel.   This is the icon	in icon/tray mode, or the full
	      gui otherwise.  You can also  specify  width  and	 height,  i.e.
	      WxH+X+Y, but it is not recommended.  In "tray" mode the geometry
	      is ignored unless	the system tray	manager	does not  seem	to  be
	      running.	  One	could	imagine	 using	something  like	 "-gui
	      tray,geom=+4000+4000" with a display manager to keep the gui in-
	      visible until someone logs in...

	      More icon	tricks,	"icon=minimal" gives an	icon just with the VNC
	      display number.  You can also set	the font with  "iconfont=...".
	      The   following	could	be  useful:  "-gui  icon=minimal,icon-

	      General examples of the -gui option: "x11vnc -gui", "x11vnc -gui
	      ez"  "x11vnc  -gui  localhost:10",  "x11vnc  -gui	 conn,host:0",
	      "x11vnc -gui tray,ez" "x11vnc -gui tray=setpass"

	      If you do	not intend to start x11vnc from	the gui	(i.e. just re-
	      mote control an existing one), then the gui process can run on a
	      different	machine	from the x11vnc	server as long	as  X  permis-
	      sions, etc. permit communication between the two.

	      FONTS: On	some systems the tk fonts can be too small, jagged, or
	      otherwise	unreadable.  There are 4 env vars you can  set	to  be
	      the tk font you prefer:

	      X11VNC_FONT_BOLD	    main   font	  for	menus	and   buttons.
	      X11VNC_FONT_FIXED	 font for fixed	width text.

	      X11VNC_FONT_BOLD_SMALL  tray icon	 font.	 X11VNC_FONT_REG_SMALL
	      tray icon	menu font.

	      The last two only	apply for the tray icon	mode.

	      Here are some examples:

	      -env	X11VNC_FONT_BOLD='Helvetica	-16	bold'	  -env
	      X11VNC_FONT_FIXED='Courier -14' -env X11VNC_FONT_REG_SMALL='Hel-
	      vetica -12'

	      You  can	put  the  lines	like the above (without	the quotes) in
	      your ~/.x11vncrc file to avoid having to	specify	 them  on  the
	      x11vnc command line.

       -remote command

	      Remotely	control	 some  aspects	of  an	already	running	x11vnc
	      server.  "-R" and	"-r" are aliases for "-remote".	 After the re-
	      mote  control  command is	sent to	the running server the 'x11vnc
	      -remote ...'  x11vnc command  exits.   You  can  often  use  the
	      -query command (see below) to see	if the x11vnc server processed
	      your -remote command.

	      The default  communication  channel  is  that  of	 X  properties
	      (specifically  X11VNC_REMOTE),  and  so this command must	be run
	      with correct settings for	DISPLAY	 and  possibly	XAUTHORITY  to
	      connect  to  the	X server and set the property.	Alternatively,
	      use the -display and -auth options to set	them  to  the  correct
	      values.	The running server cannot use the -novncconnect	option
	      because that disables the	communication channel.	See below  for
	      alternate	channels.

	      For example: 'x11vnc -remote stop' (which	is the same as 'x11vnc
	      -R stop')	will close down	the x11vnc server.  'x11vnc -R shared'
	      will  enable  shared connections,	and 'x11vnc -R scale:3/4' will
	      rescale the desktop.

	      To use a different name for the X11 property (e.g. to have sepa-
	      rate  communication  channels  for multiple x11vnc's on the same
	      display) set  the	 X11VNC_REMOTE	environment  variable  to  the
	      string  you  want,  for  example:	 -env X11VNC_REMOTE=X11VNC_RE-
	      MOTE_12345 Both sides of the channel must	use  the  same	unique

	      To  run  a  bunch	 of commands in	a sequence use something like:
	      x11vnc -R	'script:firstcmd;secondcmd;...'

	      Use x11vnc -R script:file=/path/to/file to read commands from  a
	      file (can	be multi-line and use the comment '#' character	in the
	      normal way.  The ';' separator must still	be  used  to  separate
	      each command.)

	      To  not  try  to contact another x11vnc process and instead just
	      run the command (or query) directly, prefix the command with the
	      string "DIRECT:"

	      The following -remote/-R commands	are supported:

	      stop	       terminate  the server, same as "quit" "exit" or

	      ping	      see if the x11vnc	server responds.   return  is:

	      ping:mystring    as  above, but use your own unique string.  re-
	      turn is: ans=ping:mystring:<xdisplay>

	      blacken	      try to push a black fb  update  to  all  clients
	      (due  to	timings	 a client could	miss it). Same as "zero", also
	      "zero:x1,y1,x2,y2" for a rectangle.

	      refresh	      send the entire fb to all	clients.

	      reset	      recreate the fb, polling memory, etc.

	      id:windowid     set -id window to	"windowid". empty or "root" to
	      go back to root window

	      sid:windowid    set -sid window to "windowid"

	      id_cmd:cmd	cmds:	raise,	lower,	map,  unmap,  iconify,
	      move:dXdY, resize:dWdH, geom:WxH+X+Y. dX dY,  dW,	 and  dH  must
	      have  a leading "+" or "-" e.g.: move:-30+10 resize:+20+35 also:
	      wm_delete,    wm_name:string    and    icon_name:string.	  Also

	      waitmapped      wait until subwin	is mapped.

	      nowaitmapped    do not wait until	subwin is mapped.

	      clip:WxH+X+Y    set -clip	mode to	"WxH+X+Y"

	      flashcmap	      enable  -flashcmap mode.

	      noflashcmap     disable -flashcmap mode.

	      shiftcmap:n     set -shiftcmap to	n.

	      notruecolor     enable  -notruecolor mode.

	      truecolor	      disable -notruecolor mode.

	      overlay	      enable  -overlay mode (if	applicable).

	      nooverlay	      disable -overlay mode.

	      overlay_cursor  in -overlay mode,	enable cursor drawing.

	      overlay_nocursor	disable	cursor drawing.	same as	nooverlay_cur-

	      8to24	      enable  -8to24 mode (if applicable).

	      no8to24	      disable -8to24 mode.

	      8to24_opts:str  set the -8to24 opts to "str".

	      24to32	      enable  -24to32 mode (if applicable).

	      no24to32	      disable -24to32 mode.

	      visual:vis      set -visual to "vis"

	      scale:frac      set -scale to "frac"

	      scale_cursor:f  set -scale_cursor	to "f"

	      viewonly	      enable  -viewonly	mode.

	      noviewonly      disable -viewonly	mode.

	      shared	      enable  -shared mode.

	      noshared	      disable -shared mode.

	      forever	      enable  -forever mode.

	      noforever	      disable -forever mode.

	      timeout:n	      reset -timeout to	n, if there are	 currently  no
	      clients, exit unless one connects	in the next n secs.

	      tightfilexfer   enable  filetransfer for NEW clients.

	      notightfilexfer disable filetransfer for NEW clients.

	      ultrafilexfer   enable  filetransfer for clients.

	      noultrafilexfer disable filetransfer for clients.

	      rfbversion:n.m  set -rfbversion for new clients.

	      http	      enable  http client connections.

	      nohttp	      disable http client connections.

	      deny	      deny any new connections,	same as	"lock"

	      nodeny	      allow new	connections, same as "unlock"

	      avahi	      enable  avahi service advertising.

	      noavahi	      disable avahi service advertising.

	      mdns	      enable  avahi service advertising.

	      nomdns	      disable avahi service advertising.

	      zeroconf	      enable  avahi service advertising.

	      nozeroconf      disable avahi service advertising.

	      connect:host     do  reverse connection to host, "host" may be a
	      comma separated list of  hosts  or  host:ports.	See  -connect.
	      Passwords	 required  as  with  fwd  connections.	See X11VNC_RE-

	      disconnect:host disconnect  any  clients	from  "host"  same  as
	      "close:host".   Use host "all" to	close all current clients.  If
	      you know the client internal  hex	 ID,  e.g.  0x3	 (returned  by
	      "-query clients" and RFB_CLIENT_ID) you can use that too.

	      proxy:host:port set reverse connection proxy (empty to disable).

	      allowonce:host   For  the	next connection	only, allow connection
	      from "host". In -ssl mode	 two  connections  are	allowed	 (i.e.
	      Fetch Cert) unless X11VNC_NO_SSL_ALLOW_TWICE=1

	      allow:hostlist  set -allow list to (comma	separated) "hostlist".
	      See -allow and -localhost.  Do not use with -allow /path/to/file
	      Use  "+host"  to	add a single host, and use "-host" to delete a
	      single host

	      localhost	      enable  -localhost mode

	      nolocalhost     disable -localhost mode

	      listen:str      set -listen to str, empty	to disable.

	      noipv6	      enable  -noipv6 mode.

	      ipv6	      disable -noipv6 mode.

	      noipv4	      enable  -noipv4 mode.

	      ipv4	      disable -noipv4 mode.

	      6		      enable  -6 IPv6 listening	mode.

	      no6	      disable -6 IPv6 listening	mode.

	      lookup	      disable -nolookup	mode.

	      nolookup	      enable  -nolookup	mode.

	      lookup	      disable -nolookup	mode.

	      input:str	      set -input to "str", empty to disable.

	      grabkbd	      enable  -grabkbd mode.

	      nograbkbd	      disable -grabkbd mode.

	      grabptr	      enable  -grabptr mode.

	      nograbptr	      disable -grabptr mode.

	      grabalways      enable  -grabalways mode.

	      nograbalways    disable -grabalways mode.

	      grablocal:n     set -grablocal to	n.

	      client_input:str set the K, M, B -input on a  per-client	basis.
	      select which client as for disconnect, e.g. client_input:host:MB
	      or client_input:0x2:K

	      accept:cmd      set -accept "cmd"	(empty to disable).

	      afteraccept:cmd set -afteraccept (empty to disable).

	      gone:cmd	      set -gone	"cmd" (empty to	disable).

	      noshm	      enable  -noshm mode.

	      shm	      disable -noshm mode (i.e.	use shm).

	      flipbyteorder   enable -flipbyteorder mode, you may need to  set
	      noshm for	this to	do something.

	      noflipbyteorder disable -flipbyteorder mode.

	      onetile	       enable  -onetile	mode. (you may need to set shm
	      for this to do something)

	      noonetile	      disable -onetile mode.

	      solid	      enable  -solid mode

	      nosolid	      disable -solid mode.

	      solid_color:color	set -solid color (and apply it).

	      blackout:str    set -blackout "str"  (empty  to  disable).   See
	      -blackout	 for  the  form	of "str" (basically: WxH+X+Y,...)  Use
	      "+WxH+X+Y" to append a single rectangle use "-WxH+X+Y" to	delete

	      xinerama	      enable  -xinerama	mode. (if applicable)

	      noxinerama      disable -xinerama	mode.

	      xtrap	      enable  -xtrap input mode(if applicable)

	      noxtrap	      disable -xtrap input mode.

	      xrandr	      enable  -xrandr mode. (if	applicable)

	      noxrandr	      disable -xrandr mode.

	      xrandr_mode:mode set the -xrandr mode to "mode".

	      rotate:mode     set the -rotate mode to "mode".

	      padgeom:WxH     set -padgeom to WxH (empty to disable) If	WxH is
	      "force" or "do" the padded geometry fb is	immediately applied.

	      quiet	      enable  -quiet mode.

	      noquiet	      disable -quiet mode.

	      modtweak	      enable  -modtweak	mode.

	      nomodtweak      enable  -nomodtweak mode.

	      xkb	      enable  -xkb modtweak mode.

	      noxkb	      disable -xkb modtweak mode.

	      capslock	      enable  -capslock	mode.

	      nocapslock      disable -capslock	mode.

	      skip_lockkeys   enable  -skip_lockkeys mode.

	      noskip_lockkeys disable -skip_lockkeys mode.

	      skip_keycodes:str	enable -xkb -skip_keycodes "str".

	      sloppy_keys     enable  -sloppy_keys mode.

	      nosloppy_keys   disable -sloppy_keys mode.

	      skip_dups	      enable  -skip_dups mode.

	      noskip_dups     disable -skip_dups mode.

	      add_keysyms     enable -add_keysyms mode.

	      noadd_keysyms   stop adding keysyms. those added will  still  be
	      removed at exit.

	      clear_mods      enable  -clear_mods mode and clear them.

	      noclear_mods    disable -clear_mods mode.

	      clear_keys      enable  -clear_keys mode and clear them.

	      noclear_keys    disable -clear_keys mode.

	      clear_locks     do the clear_locks action.

	      clear_all	      do the clear_all action.

	      keystate	      have x11vnc print	current	keystate.

	      remap:str	      set -remap "str" (empty to disable).  See	-remap
	      for the form of "str" (basically:	key1-key2,key3-key4,...)   Use
	      "+key1-key2"  to append a	single keymapping, use "-key1-key2" to

	      norepeat	      enable  -norepeat	mode.

	      repeat	      disable -norepeat	mode.

	      nofb	      enable  -nofb mode.

	      fb	      disable -nofb mode.

	      bell	      enable  bell (if supported).

	      nobell	      disable bell.

	      sendbell	      ring the bell now.

	      nosel	      enable  -nosel mode.

	      sel	      disable -nosel mode.

	      noprimary	      enable  -noprimary mode.

	      primary	      disable -noprimary mode.

	      nosetprimary    enable  -nosetprimary mode.

	      setprimary      disable -nosetprimary mode.

	      noclipboard     enable  -noclipboard mode.

	      clipboard	      disable -noclipboard mode.

	      nosetclipboard  enable  -nosetclipboard mode.

	      setclipboard    disable -nosetclipboard mode.

	      seldir:str      set -seldir to "str"

	      resend_cutbuffer resend the most recent CUTBUFFER0 copy

	      resend_clipboard resend the most recent CLIPBOARD	copy

	      resend_primary   resend the most recent PRIMARY copy

	      cursor:mode     enable  -cursor "mode".

	      show_cursor     enable  showing a	cursor.

	      noshow_cursor   disable showing a	cursor.	(same as "nocursor")

	      cursor_drag     enable  cursor changes during drag.

	      nocursor_drag   disable cursor changes during drag.

	      arrow:n	      set -arrow to alternate n.

	      xfixes	      enable  xfixes cursor shape mode.

	      noxfixes	      disable xfixes cursor shape mode.

	      alphacut:n      set -alphacut to n.

	      alphafrac:f     set -alphafrac to	f.

	      alpharemove     enable  -alpharemove mode.

	      noalpharemove   disable -alpharemove mode.

	      alphablend      disable -noalphablend mode.

	      noalphablend    enable  -noalphablend mode.

	      cursorshape     disable -nocursorshape mode.

	      nocursorshape   enable  -nocursorshape mode.

	      cursorpos	      disable -nocursorpos mode.

	      nocursorpos     enable  -nocursorpos mode.

	      xwarp	      enable  -xwarppointer mode.

	      noxwarp	      disable -xwarppointer mode.

	      always_inject   enable  -always_inject mode.

	      noalways_inject disable -always_inject mode.

	      buttonmap:str   set -buttonmap "str", empty to disable

	      dragging	      disable -nodragging mode.

	      nodragging      enable  -nodragging mode.

	      ncache	      reenable -ncache mode.

	      noncache	      disable  -ncache mode.

	      ncache_size:n   set -ncache size to n.

	      ncache_cr	      enable  -ncache_cr mode.

	      noncache_cr     disable -ncache_cr mode.

	      ncache_no_moveraise     enable  no_moveraise mode.

	      noncache_no_moveraise   disable no_moveraise mode.

	      ncache_no_dtchange      enable  ncache_no_dtchange mode.

	      noncache_no_dtchange    disable ncache_no_dtchange mode.

	      ncache_old_wm	      enable  ncache_old_wm mode.

	      noncache_old_wm	      disable ncache_old_wm mode.

	      ncache_no_rootpixmap    enable  ncache_no_rootpixmap.

	      noncache_no_rootpixmap  disable ncache_no_rootpixmap.

	      ncache_reset_rootpixmap recheck the root pixmap, ncrp

	      ncache_keep_anims	      enable  ncache_keep_anims.

	      noncache_keep_anims     disable ncache_keep_anims.

	      ncache_pad:n    set -ncache_pad to n.

	      wireframe	      enable  -wireframe mode. same as "wf"

	      nowireframe     disable -wireframe mode. same as "nowf"

	      wireframe:str   enable  -wireframe mode string.

	      wireframe_mode:str enable	 -wireframe mode string.

	      wireframelocal  enable  wireframelocal. same as "wfl"

	      nowireframe     disable wireframelocal. same as "nowfl"

	      wirecopyrect:str set -wirecopyrect string. same as "wcr:"

	      scrollcopyrect:str set -scrollcopyrect string. same "scr"

	      noscrollcopyrect disable -scrollcopyrect__mode_. "noscr"

	      scr_area:n      set -scr_area to n

	      scr_skip:list   set -scr_skip to "list"

	      scr_inc:list    set -scr_inc to "list"

	      scr_keys:list   set -scr_keys to "list"

	      scr_term:list   set -scr_term to "list"

	      scr_keyrepeat:str	set -scr_keyrepeat to "str"

	      scr_parms:str   set -scr_parms parameters.

	      fixscreen:str   set -fixscreen to	"str".

	      noxrecord	      disable all use of RECORD	extension.

	      xrecord	      enable  use of RECORD extension.

	      reset_record    reset RECORD extension (if avail.)

	      pointer_mode:n  set -pointer_mode	to n. same as "pm"

	      input_skip:n    set -input_skip to n.

	      allinput	      enable  use of -allinput mode.

	      noallinput      disable use of -allinput mode.

	      input_eagerly   enable  use of -input_eagerly mode.

	      noinput_eagerly disable use of -input_eagerly mode.

	      ssltimeout:n    set -ssltimeout to n.

	      speeds:str      set -speeds to str.

	      wmdt:str	      set -wmdt	to str.

	      debug_pointer   enable  -debug_pointer, same as "dp"

	      nodebug_pointer disable -debug_pointer, same as "nodp"

	      debug_keyboard   enable  -debug_keyboard,	same as	"dk"

	      nodebug_keyboard disable -debug_keyboard,	same as	"nodk"

	      keycode:n	      inject keystroke 'keycode' (xmodmap -pk)

	      keycode:n,down  inject 'keycode' (down=0,1)

	      keysym:str      inject keystroke 'keysym'	(number/name)

	      keysym:str,down inject 'keysym' (down=0,1)

	      ptr:x,y,mask    inject pointer event x, y, button-mask

	      fakebuttonevent:button,down direct XTestFakeButtonEvent.

	      sleep:t	      sleep floating point time	t.

	      get_xprop:p     get X property named 'p'.

	      set_xprop:p:val set  X  property	named  'p'  to	'val'.	 p  ->
	      id=NNN:p for hex/dec window id.

	      wininfo:id      get info about X window id.  use 'root' for root
	      window, use +id for children.

	      grab_state      get state	of pointer and keyboard	grab.

	      pointer_pos     print XQueryPointer x,y cursor position.

	      pointer_x	      print XQueryPointer x cursor position.

	      pointer_y	      print XQueryPointer y cursor position.

	      pointer_same    print XQueryPointer ptr on same screen.

	      pointer_root    print XQueryPointer curr ptr rootwin.

	      pointer_mask    print XQueryPointer button and mods mask

	      mouse_x	      print x11vnc's idea of cursor position.

	      mouse_y	      print x11vnc's idea of cursor position.

	      noop	      do nothing.

	      defer:n	      set -defer to n ms,same as deferupdate:n

	      wait:n	      set -wait	to n ms.

	      extra_fbur:n    set -extra_fbur to n.

	      wait_ui:f	      set -wait_ui factor to f.

	      setdefer:n      set -setdefer to -2,-1,0,1, or 2.

	      wait_bog	      disable -nowait_bog mode.

	      nowait_bog      enable  -nowait_bog mode.

	      slow_fb:f	      set -slow_fb to f	seconds.

	      xrefresh:f      set -xrefresh to f seconds.

	      readtimeout:n   set read timeout to n seconds.

	      nap	      enable  -nap mode.

	      nonap	      disable -nap mode.

	      sb:n	      set -sb to n s, same as screen_blank:n

	      fbpm	      disable -nofbpm mode.

	      nofbpm	      enable  -nofbpm mode.

	      dpms	      disable -nodpms mode.

	      nodpms	      enable  -nodpms mode.

	      forcedpms	      enable  -forcedpms mode.

	      noforcedpms     disable -forcedpms mode.

	      clientdpms      enable  -clientdpms mode.

	      noclientdpms    disable -clientdpms mode.

	      noserverdpms    enable  -noserverdpms mode.

	      serverdpms      disable -noserverdpms mode.

	      noultraext      enable  -noultraext mode.

	      ultraext	      disable -noultraext mode.

	      chatwindow      enable  local chatwindow mode.

	      nochatwindow    disable local chatwindow mode.

	      chaton	      begin chat using local window.

	      chatoff	      end   chat using local window.

	      xdamage	      enable  xdamage polling hints.

	      noxdamage	      disable xdamage polling hints.

	      xd_area:A	      set -xd_area max pixel area to "A"

	      xd_mem:f	      set -xd_mem remembrance to "f"

	      fs:frac	      set -fs fraction to "frac", e.g. 0.5

	      gaps:n	      set -gaps	to n.

	      grow:n	      set -grow	to n.

	      fuzz:n	      set -fuzz	to n.

	      snapfb	      enable  -snapfb mode.

	      nosnapfb	      disable -snapfb mode.

	      rawfb:str	      set -rawfb mode to "str".

	      uinput_accel:f  set uinput_accel to f.

	      uinput_thresh:n set uinput_thresh	to n.

	      uinput_reset:n  set uinput_reset to n ms.

	      uinput_always:n set uinput_always	to 1/0.

	      progressive:n   set LibVNCServer -progressive slice  height  pa-
	      rameter to n.

	      desktop:str     set -desktop name	to str for new clients.

	      rfbport:n	      set -rfbport to n.

	      macnosaver      enable  -macnosaver mode.

	      macsaver	      disable -macnosaver mode.

	      macnowait	      enable  -macnowait  mode.

	      macwait	      disable -macnowait  mode.

	      macwheel:n      set -macwheel to n.

	      macnoswap	      enable  -macnoswap mouse button mode.

	      macswap	      disable -macnoswap mouse button mode.

	      macnoresize     enable  -macnoresize mode.

	      macresize	      disable -macnoresize mode.

	      maciconanim:n   set -maciconanim to n.

	      macmenu	      enable  -macmenu	mode.

	      macnomenu	      disable -macmenu	mode.

	      macuskbd	      enable  -macuskbd	mode.

	      macnouskbd      disable -macuskbd	mode.

	      httpport:n      set -httpport to n.

	      httpdir:dir     set -httpdir to dir (and enable http).

	      enablehttpproxy	enable	-enablehttpproxy mode.

	      noenablehttpproxy	disable	-enablehttpproxy mode.

	      alwaysshared     enable  -alwaysshared mode.

	      noalwaysshared	disable	 -alwaysshared	mode.	(may interfere
	      with other options)

	      nevershared      enable  -nevershared mode.

	      nonevershared    disable -nevershared mode.  (may	interfere with
	      other options)

	      dontdisconnect   enable  -dontdisconnect mode.

	      nodontdisconnect	disable	 -dontdisconnect mode.	(may interfere
	      with other options)

	      debug_xevents   enable  debugging	X events.

	      nodebug_xevents disable debugging	X events.

	      debug_xdamage   enable  debugging	X DAMAGE mechanism.

	      nodebug_xdamage disable debugging	X DAMAGE mechanism.

	      debug_wireframe enable   debugging wireframe mechanism.

	      nodebug_wireframe	disable	debugging wireframe mechanism.

	      debug_scroll    enable  debugging	scrollcopy mechanism.

	      nodebug_scroll  disable debugging	scrollcopy mechanism.

	      debug_tiles     enable  -debug_tiles

	      nodebug_tiles   disable -debug_tiles

	      debug_grabs     enable  -debug_grabs

	      nodebug_grabs   disable -debug_grabs

	      debug_sel	      enable  -debug_sel

	      nodebug_sel     disable -debug_sel

	      debug_ncache    enable  -debug_ncache

	      nodebug_ncache  disable -debug_ncache

	      dbg	      enable  -dbg crash shell

	      nodbg	      disable -dbg crash shell

	      noremote	      disable the -remote command processing, it  can-
	      not be turned back on.

	      bcx_xattach:str  This remote control command is for use with the
	      BARCO xattach program or the x2x program.	 Both  of  these  pro-
	      grams  are for 'pointer and keyboard' sharing between separate X
	      displays.	 In general the	two displays are usually nearby,  e.g.
	      on  the  same  desk,  and	this allows the	user to	share a	single
	      pointer and keyboard between them.  The user moves the mouse  to
	      an  edge	and  then  the	mouse pointer appears to 'jump'	to the
	      other display screen.  Thus it emulates what a single  X	server
	      would  do	for two	screens	(e.g. :0.0 and :0.1) The illusion of a
	      single Xserver with multiple screens is achieved	by  forwarding
	      events to	the 2nd	one via	the XTEST extension.

	      What  the	 x11vnc	 bcx_xattach  command  does is to perform some
	      pointer movements	to try to INDUCE xattach/x2x to	'jump' to  the
	      other  display.	In what	follows	the 'master' display refers to
	      the one that when	it has 'focus' it is basically	doing  nothing
	      besides  watching	for the	mouse to go over an edge.  The 'slave'
	      display refers to	the one	to which the  mouse  and  keyboard  is
	      redirected to once an edge in the	master has been	crossed.  Note
	      that the x11vnc executing	the bcx_xattach	command	 MUST  be  the
	      one connected to the *master* display.

	      Also  note  that when input is being redirected (via XTEST) from
	      the master display to the	slave display,	the  master  display's
	      pointer  and  keyboard are *grabbed* by xattach/x2x.  x11vnc can
	      use this info to verify that the master/slave  mode  change  has
	      taken  place  correctly.	 If  you specify the "ifneeded"	option
	      (see below) and the initial grab state is	that  of  the  desired
	      final   state,  then  no	pointer	 movements  are	 injected  and
	      "DONE,GRAB_OK" is	returned.

	      "str" must contain one of	"up", "down", "left",  or  "right"  to
	      indicate	the  direction of the 'jump'.  "str" must also contain
	      one of "master_to_slave" or "slave_to_master"  to	 indicate  the
	      type of mode change induced by the jump.	Use "M2S" and "S2M" as
	      shorter aliases.

	      "str" may	be a "+" separated list	of additional tuning  options.
	      The  "shift=n"  option  indicates	 an offset shift position away
	      from (0,0) (default 20).	"final=x+y" specifies the final	 posi-
	      tion  of	the cursor at the end of the normal move sequence; de-
	      fault 30+30.  "extra_move=x+y" means to do one more pointer move
	      after  "final"  to x+y.  "dt=n" sets the sleep time in millisec-
	      onds between pointer moves (default: 40ms)  "retry=n"  specifies
	      the  maximum  number  of retries if the grab state change	fails.
	      "ifneeded" means to not apply the	pointer	movements if the  ini-
	      tial  grab  state	 is  that  of  the  desired  final state. "no-
	      grabcheck" means to not check if the grab	state changed  as  ex-
	      pected and only apply the	pointer	movements (default is to check
	      the grab states.)

	      If you do	not specify "up", etc.,	to bcx_xattach nothing will be
	      attempted	 and  the  command  returns  the string	FAIL,NO_DIREC-
	      TION_SPECIFIED.  If you  do  not	specify	 "master_to_slave"  or
	      "M2S",  etc.,  to	 bcx_xattach nothing will be attempted and the
	      command returns the string FAIL,NO_MODE_CHANGE_SPECIFIED.

	      Otherwise, the returned string will contain "DONE".  It will  be
	      "DONE,GRAB_OK"  if  the  grab  state  changed as expected	(or if
	      "ifneeded" was supplied and the initial grab state  was  already
	      the  desired one.)  If the initial grab state was	incorrect, but
	      the   final   grab   state    was	   correct    then    it    is
	      "DONE,GRAB_FAIL_INIT".   If  the initial grab state was correct,
	      but  the	final  grab   state   was   incorrect	then   it   is
	      "DONE,GRAB_FAIL_FINAL".	If  both  are  incorrect  it  will  be
	      "DONE,GRAB_FAIL".	 Under grab failure the	string	will  be  fol-
	      lowed  by	 ":p1,k1-p2,k2"	 where	 p1,k1	indicates  the initial
	      pointer and keyboard grab	states and p2,k2 the  final  ones.  If
	      GRAB_FAIL	 or GRAB_FAIL_FINAL occurs, the	action will be retried
	      up to 3 times; trying to reset the state and sleeping a bit  be-
	      tween  each  try.	  Set retry=n to adjust	the number of retries,
	      zero to disable retries.

	      Examples:	 -R  bcx_xattach:down+M2S  -R  bcx_xattach:up+S2M   -R
	      bcx_xattach:up+S2M+nograbcheck+dt=30 -R bcx_xattach:down+M2S+ex-

	      or use -Q	instead	of -R to retrieve the result text.

	      End of the bcx_xattach:str description.

	      The vncconnect(1)	command	from standard  VNC  distributions  may
	      also  be used if string is prefixed with "cmd=" E.g. 'vncconnect
	      cmd=stop'.  Under	some circumstances xprop(1)  can  used	if  it
	      supports -set (see the FAQ).

	      If  "-connect  /path/to/file"  has  been supplied	to the running
	      x11vnc server then that file can	be  used  as  a	 communication
	      channel  (this  is  the  only  way to remote control one of many
	      x11vnc's polling the same	X display) Simply run:	'x11vnc	 -con-
	      nect  /path/to/file  -remote  ...'  or you can directly write to
	      the file via something like: "echo  cmd=stop  >  /path/to/file",

       -query variable

	      Like  -remote, except just query the value of variable.  "-Q" is
	      an alias for "-query".  Multiple queries can be done by separat-
	      ing variables by commas, e.g. -query var1,var2. The results come
	      back in the  form	 ans=var1:value1,ans=var2:value2,...   to  the
	      standard output.	If a variable is read-only, it comes back with
	      prefix "aro=" instead of "ans=".

	      Some -remote commands are	pure actions that do not make sense as
	      variables, e.g. "stop" or	"disconnect", in these cases the value
	      returned is "N/A".  To direct a query straight to	the X11VNC_RE-
	      MOTE property or connect file use	"qry=..." instead of "cmd=..."

	      ans=  stop quit exit shutdown ping resend_cutbuffer resend_clip-
	      board resend_primary blacken zero	refresh	reset close disconnect
	      id_cmd id	sid waitmapped nowaitmapped clip flashcmap noflashcmap
	      shiftcmap	truecolor notruecolor overlay nooverlay	overlay_cursor
	      overlay_yescursor	 nooverlay_nocursor  nooverlay_cursor  noover-
	      lay_yescursor overlay_nocursor 8to24 no8to24  8to24_opts	24to32
	      no24to32	visual	scale  scale_cursor viewonly noviewonly	shared
	      noshared forever noforever once timeout  tightfilexfer  notight-
	      filexfer	ultrafilexfer  noultrafilexfer	rfbversion  deny  lock
	      nodeny unlock avahi mdns zeroconf	noavahi	nomdns nozeroconf con-
	      nect  proxy allowonce allow noipv6 ipv6 noipv4 ipv4 no6 6	local-
	      host nolocalhost listen lookup nolookup accept afteraccept  gone
	      shm   noshm   flipbyteorder  noflipbyteorder  onetile  noonetile
	      solid_color solid	nosolid	 blackout  xinerama  noxinerama	 xtrap
	      noxtrap  xrandr  noxrandr	xrandr_mode rotate padgeom quiet q no-
	      quiet  modtweak  nomodtweak  xkb	 noxkb	 capslock   nocapslock
	      skip_lockkeys    noskip_lockkeys	  skip_keycodes	   sloppy_keys
	      nosloppy_keys skip_dups  noskip_dups  add_keysyms	 noadd_keysyms
	      clear_mods   noclear_mods	  clear_keys   noclear_keys  clear_all
	      clear_locks keystate remap repeat	norepeat fb nofb  bell	nobell
	      sendbell	sel  nosel  primary  noprimary setprimary nosetprimary
	      clipboard	noclipboard setclipboard nosetclipboard	seldir cursor-
	      shape  nocursorshape  cursorpos  nocursorpos  cursor_drag	nocur-
	      sor_drag cursor show_cursor noshow_cursor	nocursor arrow	xfixes
	      noxfixes xdamage noxdamage xd_area xd_mem	alphacut alphafrac al-
	      pharemove	 noalpharemove	alphablend  noalphablend  xwarppointer
	      xwarp  noxwarppointer noxwarp always_inject noalways_inject but-
	      tonmap	 dragging     nodragging     ncache_cr	   noncache_cr
	      ncache_no_moveraise   noncache_no_moveraise   ncache_no_dtchange
	      noncache_no_dtchange ncache_no_rootpixmap	noncache_no_rootpixmap
	      ncache_reset_rootpixmap ncrp ncache_keep_anims noncache_keep_an-
	      ims ncache_old_wm	 noncache_old_wm  ncache_pad  ncache  noncache
	      ncache_size debug_ncache nodebug_ncache wireframe_mode wireframe
	      wf nowireframe nowf wireframelocal  wfl  nowireframelocal	 nowfl
	      wirecopyrect  wcr	nowirecopyrect nowcr scr_area scr_skip scr_inc
	      scr_keys scr_term	scr_keyrepeat scr_parms	scrollcopyrect scr no-
	      scrollcopyrect  noscr  fixscreen	noxrecord xrecord reset_record
	      pointer_mode pm  input_skip  allinput  noallinput	 input_eagerly
	      noinput_eagerly  input  grabkbd nograbkbd	grabptr	nograbptr gra-
	      balways nograbalways grablocal  client_input  ssltimeout	speeds
	      wmdt  debug_pointer  dp  nodebug_pointer	nodp debug_keyboard dk
	      nodebug_keyboard nodk keycode keysym ptr	fakebuttonevent	 sleep
	      get_xprop	set_xprop wininfo bcx_xattach deferupdate defer	setde-
	      fer extra_fbur wait_ui wait_bog nowait_bog slow_fb xrefresh wait
	      readtimeout  nap	nonap  sb screen_blank fbpm nofbpm dpms	nodpms
	      clientdpms  noclientdpms	forcedpms   noforcedpms	  noserverdpms
	      serverdpms  noultraext  ultraext	chatwindow nochatwindow	chaton
	      chatoff fs gaps grow fuzz	 snapfb	 nosnapfb  rawfb  uinput_accel
	      uinput_thresh  uinput_reset  uinput_always  progressive  rfbport
	      http nohttp httpport httpdir  enablehttpproxy  noenablehttpproxy
	      alwaysshared  noalwaysshared nevershared noalwaysshared dontdis-
	      connect nodontdisconnect desktop	debug_xevents  nodebug_xevents
	      debug_xevents  debug_xdamage  nodebug_xdamage  debug_xdamage de-
	      bug_wireframe  nodebug_wireframe	debug_wireframe	  debug_scroll
	      nodebug_scroll  debug_scroll debug_tiles dbt nodebug_tiles nodbt
	      debug_tiles debug_grabs nodebug_grabs debug_sel nodebug_sel  dbg
	      nodbg  macnosaver	macsaver nomacnosaver macnowait	macwait	nomac-
	      nowait macwheel macnoswap	macswap	nomacnoswap macnoresize	macre-
	      size  nomacnoresize  maciconanim macmenu macnomenu nomacmenu ma-
	      cuskbd nomacuskbd	noremote

	      aro=  noop display vncdisplay  icon_mode	autoport  loop	loopbg
	      desktopname  guess_desktop  guess_dbus http_url auth xauth users
	      rootshift	 clipshift  scale_str  scaled_x	 scaled_y  scale_numer
	      scale_denom  scale_fac_x	scale_fac_y  scaling_blend scaling_no-
	      mult4 scaling_pad	scaling_interpolate  inetd  privremote	unsafe
	      safer   nocmds  passwdfile  unixpw  unixpw_nis  unixpw_list  ssl
	      ssl_pem sslverify	stunnel	stunnel_pem https httpsredir usepw us-
	      ing_shm  logfile	o flag rmflag rc norc h	help V version lastmod
	      bg sigpipe threads readrate netrate netlatency pipeinput clients
	      client_count   pid   ext_xtest   ext_xtrap  ext_xrecord  ext_xkb
	      ext_xshm	 ext_xinerama	ext_overlay   ext_xfixes   ext_xdamage
	      ext_xrandr   rootwin  num_buttons	 button_mask  mouse_x  mouse_y
	      grab_state   pointer_pos	 pointer_x   pointer_y	  pointer_same
	      pointer_root  pointer_mask  bpp  depth indexed_color dpy_x dpy_y
	      wdpy_x wdpy_y off_x off_y	cdpy_x cdpy_y  coff_x  coff_y  rfbauth
	      passwd viewpasswd

       -QD variable

	      Just  like  -query  variable,  but returns the default value for
	      that parameter (no running x11vnc	server is consulted)


	      By default -remote commands are run asynchronously, that is, the
	      request  is posted and the program immediately exits.  Use -sync
	      to have the program wait for an acknowledgement from the	x11vnc
	      server  that command was processed (somehow).  On	the other hand
	      -query requests are always processed synchronously because  they
	      have to wait for the answer.

	      Also  note that if both -remote and -query requests are supplied
	      on the command  line,  the  -remote  is  processed  first	 (syn-
	      chronously:  no  need for	-sync),	and then the -query request is
	      processed	in the normal way.  This allows	for a reliable way  to
	      see if the -remote command was processed by querying for any new
	      settings.	 Note however that there is timeout of a  few  seconds
	      (see the next paragraph) so if the x11vnc	takes longer than that
	      to process the requests the requester will think that a  failure
	      has taken	place.

	      The  default  is	to  wait 3.5 seconds.  Or if cmd=stop only 1.0
	      seconds.	If cmd matches 'script:' then it will wait up to  10.0
	      seconds.	 Set  X11VNC_SYNC_TIMEOUT to the number	of seconds you
	      want it to wait.

       -query_retries str

	      If a query fails to get a	response from an x11vnc	server,	 retry
	      up  to  n	 times.	 str is	specified as n[:t][/match]  Optionally
	      the delay	between	tries may be specified by "t" a	floating point
	      time  (default  0.5 seconds.)  Note: the response	is not checked
	      for validity or whether it corresponds to	the query  sent.   The
	      query  "ping:mystring" may be used to help uniquely identify the
	      query.  Optionally, a matching string after a "/"	will  be  used
	      to check the result text.	 Up to n retries will take place until
	      the matching string is found in the output text.	If  the	 match
	      string is	never found the	program's exit code is 1; if the match
	      is found it exits	with 0.	 Note that there may be	stdout printed
	      for each retry (i.e. multiple lines printed out to stdout.)  Ex-
	      ample: -query_retries 4:1.5/grab_state

       -remote_prefix str

	      Enable a remote-control communication channel for	connected  VNC
	      clients.	 str is	a non-empty string. If a VNC client sends rfb-
	      CutText having the prefix	str then the part  after  it  is  pro-
	      cessed  as  though it were sent via 'x11vnc -remote ...'.	 If it
	      begins with neither 'cmd=' nor 'qry=' then  'qry='  is  assumed.
	      Any corresponding	output text for	that remote control command is
	      sent back	to all client as rfbCutText.  The returned  output  is
	      also prefixed with str.  Example:	-remote_prefix DO_THIS:

	      Note  that enabling -remote_prefix allows	the remote VNC viewers
	      to run x11vnc -remote commands.  Do not use this option if  they
	      are not to be trusted.

       -noremote, -yesremote

	      Do  not  process	any  remote  control  commands or queries.  Do
	      process remote control commands or queries.  Default: -yesremote

	      A	note about security wrt	remote control commands.   If  someone
	      can  connect to the X display and	change the property X11VNC_RE-
	      MOTE, then they can remotely control x11vnc.  Normally access to
	      the  X  display  is  protected.	Note  that  if they can	modify
	      X11VNC_REMOTE on the X server, they have enough  permissions  to
	      also  run	their own x11vnc and thus have complete	control	of the
	      desktop.	If the	 "-connect  /path/to/file"  channel  is	 being
	      used,  obviously	anyone	who can	write to /path/to/file can re-
	      motely control x11vnc.  So be sure to protect the	X display  and
	      that file's write	permissions.  See -privremote below.

	      If  you  are  paranoid  and do not think -noremote is enough, to
	      disable  the  X11VNC_REMOTE  property  channel  completely   use
	      -novncconnect,  or  use the -safer option	that shuts many	things


	      A	few  remote  commands  are  disabled  by  default  (currently:
	      id:pick,	accept:<cmd>,  gone:<cmd>,  and	rawfb:setup:<cmd>) be-
	      cause they are associated	with running  external	programs.   If
	      you  specify -unsafe, then these remote-control commands are al-
	      lowed.  Note that	you can	still specify these parameters on  the
	      command line, they just cannot be	invoked	via remote-control.


	      Equivalent  to: -novncconnect -noremote and prohibiting -gui and
	      the -connect file. Shuts off communcation	channels.


	      Perform some sanity checks and disable  remote-control  commands
	      if  it  appears that the X DISPLAY and/or	connectfile can	be ac-
	      cessed by	other users.  Once remote-control is disabled it  can-
	      not be turned back on.


	      No  external  commands  (e.g.   system(3)	, popen(3) , exec(3) )
	      will be run at all.

       -allowedcmds list

	      list contains a comma separated list of the only	external  com-
	      mands that can be	run.  The full list of associated options is:

	      stunnel,	ssl,  unixpw, WAIT, zeroconf, id, accept, afteraccept,
	      gone,  pipeinput,	  v4l-info,   rawfb-setup,   dt,   gui,	  ssh,
	      storepasswd, passwdfile, custom_passwd, findauth,	crash.

	      See each option's	help to	learn the associated external command.
	      Note that	the -nocmds option takes precedence and	 disables  all
	      external commands.


	      For  use	with  -remote  nodeny:	start out denying all incoming
	      clients until "-remote nodeny" is	used to	let them in.

       These options are passed	to LibVNCServer:

       -rfbport	port

	      TCP port for RFB protocol

       -rfbwait	time

	      max time in ms to	wait for RFB client

       -rfbauth	passwd-file

	      use authentication on RFB	 protocol  (use	 'x11vnc  -storepasswd
	      pass file' to create a password file)

       -rfbversion 3.x

	      Set the version of the RFB we choose to advertise


	      permit file transfer support

       -passwd plain-password

	      use  authentication (use plain-password as password, USE AT YOUR

       -deferupdate time

	      time in ms to defer updates (default 40)

       -deferptrupdate time

	      time in ms to defer pointer updates (default none)

       -desktop	name

	      VNC desktop name (default	"LibVNCServer")


	      always treat new clients as shared


	      never treat new clients as shared


	      don't disconnect existing	clients	when a new non-shared  connec-
	      tion comes in (refuse new	connection instead)

       -httpdir	dir-path

	      enable http server using dir-path	home

       -httpport portnum

	      use portnum for http connection


	      enable http proxy	support

       -progressive height

	      enable progressive updating for slow links

       -listen ipaddr

	      listen  for  connections	only  on  network  interface with addr
	      ipaddr. '-listen localhost' and hostname work too.

       libvncserver-tight-extension options:


	      disable file transfer

       -ftproot	string

	      set ftp root

       $HOME/.x11vncrc,	$HOME/.Xauthority


       The following are set for the auxiliary commands	run by -accept,	 -gone
       and other cases:


       vncviewer(1),  vncpasswd(1),  vncconnect(1),   vncserver(1),   Xvnc(1),
       xev(1),	xdpyinfo(1),  xwininfo(1),  xprop(1),  xmodmap(1),  xrandr(1),
       Xserver(1),  xauth(1),  xhost(1),  Xsecurity(7),	 xmessage(1),  XGetIm-
       age(3X11),  ipcrm(1),  inetd(1),	 xdm(1), gdm(1), kdm(1), ssh(1), stun-
       nel(8),	 su(1),,,,,

       x11vnc was written by Karl J. Runge <>, it  is  part
       of  the	LibVNCServer project <>.
       This manual page	is  based  one	the  one  written  by  Ludovic	Drolez
       <>,  for the Debian project (both may be used by oth-

x11vnc				 February 2018			     X11VNC(1)


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