Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
XDM(1)			    General Commands Manual			XDM(1)

NAME
       xdm - X Display Manager with support for	XDMCP, host chooser

SYNOPSIS
       xdm [ -config configuration_file	] [ -nodaemon ]	[ -debug debug_level ]
       [ -error	error_log_file	]  [  -resources  resource_file	 ]  [  -server
       server_entry ] [	-session session_program ]

DESCRIPTION
       Xdm  manages a collection of X displays,	which may be on	the local host
       or remote servers.  The design of xdm was guided	by the needs of	X ter-
       minals  as well as The Open Group standard XDMCP, the X Display Manager
       Control Protocol.  Xdm provides services	similar	to those  provided  by
       init,  getty and	login on character terminals: prompting	for login name
       and password, authenticating the	user, and running a ``session.''

       A ``session'' is	defined	by the lifetime	of a  particular  process;  in
       the  traditional	character-based	terminal world,	it is the user's login
       shell.  In the xdm context, it is an arbitrary session  manager.	  This
       is  because  in	a  windowing environment, a user's login shell process
       does not	necessarily have any terminal-like  interface  with  which  to
       connect.	  When	a real session manager is not available, a window man-
       ager or terminal	emulator is typically used as the ``session manager,''
       meaning that termination	of this	process	terminates the user's session.

       When  the  session  is terminated, xdm resets the X server and (option-
       ally) restarts the whole	process.

       When xdm	receives an Indirect query via XDMCP, it  can  run  a  chooser
       process to perform an XDMCP BroadcastQuery (or an XDMCP Query to	speci-
       fied hosts) on behalf of	the display and	offer a	menu of	possible hosts
       that  offer  XDMCP  display  management.	 This feature is useful	with X
       terminals that do not offer a host menu themselves.

       Xdm can be configured to	ignore BroadcastQuery messages	from  selected
       hosts.	This is	useful when you	don't want the host to appear in menus
       produced	by chooser or X	terminals themselves.

       Because xdm provides the	first interface	that users  will  see,	it  is
       designed	 to  be	 simple	to use and easy	to customize to	the needs of a
       particular site.	 Xdm has many options, most of which  have  reasonable
       defaults.   Browse through the various sections of this manual, picking
       and choosing the	things you want	to change.  Pay	 particular  attention
       to  the	Session	Program	section, which will describe how to set	up the
       style of	session	desired.

OVERVIEW
       xdm is highly configurable, and most of its behavior can	be  controlled
       by  resource  files  and	shell scripts.	The names of these files them-
       selves are resources read from the file xdm-config or the file named by
       the -config option.

       xdm  offers  display  management	 two  different	ways.  It can manage X
       servers running on the local machine and	specified in Xservers, and  it
       can  manage  remote  X servers (typically X terminals) using XDMCP (the
       XDM Control Protocol) as	specified in the Xaccess file.

       The resources of	the X clients run by xdm outside the  user's  session,
       including  xdm's	own login window, can be affected by setting resources
       in the Xresources file.

       For X terminals that do not offer a menu	of hosts to get	 display  man-
       agement from, xdm can collect willing hosts and run the chooser program
       to offer	the user a menu.  For X	displays attached to a host, this step
       is typically not	used, as the local host	does the display management.

       After  resetting	 the X server, xdm runs	the Xsetup script to assist in
       setting up the screen the user sees along with the xlogin widget.

       The xlogin widget, which	xdm presents, offers the  familiar  login  and
       password	prompts.

       After the user logs in, xdm runs	the Xstartup script as root.

       Then  xdm  runs	the  Xsession script as	the user.  This	system session
       file may	do some	additional startup and typically  runs	the  .xsession
       script  in  the user's home directory.  When the	Xsession script	exits,
       the session is over.

       At the end of the session, the Xreset script is run to clean up,	the  X
       server is reset,	and the	cycle starts over.

       The  file   /var/log/xdm.log  will  contain error messages from xdm and
       anything	output to stderr by  Xsetup,  Xstartup,	 Xsession  or  Xreset.
       When  you  have	trouble	getting	xdm working, check this	file to	see if
       xdm has any clues to the	trouble.

OPTIONS
       All of these options, except -config itself, specify  values  that  can
       also be specified in the	configuration file as resources.

       -config configuration_file
	      Names  the configuration file, which specifies resources to con-
	      trol the behavior	of xdm.	 /usr/local/lib/X11/xdm/xdm-config  is
	      the default.  See	the section Configuration File.

       -nodaemon
	      Specifies	 ``false'' as the value	for the	DisplayManager.daemon-
	      Mode resource.  This  suppresses	the  normal  daemon  behavior,
	      which  is	 for  xdm  to close all	file descriptors, disassociate
	      itself from the controlling terminal,  and  put  itself  in  the
	      background when it first starts up.

       -debug debug_level
	      Specifies	 the  numeric  value for the DisplayManager.debugLevel
	      resource.	 A non-zero value causes xdm to	print lots  of	debug-
	      ging  statements	to the terminal; it also disables the Display-
	      Manager.daemonMode resource, forcing xdm to  run	synchronously.
	      To interpret these debugging messages, a copy of the source code
	      for xdm is almost	a necessity.  No  attempt  has	been  made  to
	      rationalize or standardize the output.

       -error error_log_file
	      Specifies	  the	value	for   the  DisplayManager.errorLogFile
	      resource.	 This file contains errors from	xdm as	well  as  any-
	      thing  written to	stderr by the various scripts and programs run
	      during the progress of the session.

       -resources resource_file
	      Specifies	the value for the  DisplayManager*resources  resource.
	      This  file  is  loaded  using  xrdb(1)  to specify configuration
	      parameters for the authentication	widget.

       -server server_entry
	      Specifies	the value  for	the  DisplayManager.servers  resource.
	      See  the section Local Server Specification for a	description of
	      this resource.

       -udpPort	port_number
	      Specifies	the value for the DisplayManager.requestPort resource.
	      This  sets  the  port-number  which  xdm	will monitor for XDMCP
	      requests.	 If set	to 0, xdm will not listen for XDMCP or Chooser
	      requests.	 As XDMCP uses the registered well-known UDP port 177,
	      this resource should not be changed to a	value  other  than  0,
	      except for debugging.

       -session	session_program
	      Specifies	 the  value  for  the DisplayManager*session resource.
	      This indicates the program to run	as the session after the  user
	      has logged in.

       -xrm resource_specification
	      Allows an	arbitrary resource to be specified, as in most X Tool-
	      kit applications.

RESOURCES
       At many stages the actions of xdm can be	controlled through the use  of
       its  configuration  file,  which	 is  in	 the  X	resource format.  Some
       resources modify	the behavior of	xdm on all displays, while others mod-
       ify  its	 behavior on a single display.	Where actions relate to	a spe-
       cific display, the display name is  inserted  into  the	resource  name
       between ``DisplayManager'' and the final	resource name segment.

       For  local  displays,  the resource name	and class are as read from the
       Xservers	file.

       For remote displays, the	resource name is what the network  address  of
       the display resolves to.	 See the removeDomain resource.	 The name must
       match exactly; xdm is not aware of all the network aliases  that	 might
       reach a given display.  If the name resolve fails, the address is used.
       The resource class is as	sent  by  the  display	in  the	 XDMCP	Manage
       request.

       Because	the  resource  manager uses colons to separate the name	of the
       resource	from its value and dots	to separate resource name  parts,  xdm
       substitutes  underscores	 for  both dots	and colons when	generating the
       resource	name.  For example, DisplayManager.expo_x_org_0.startup	is the
       name  of	 the  resource	which  defines	the startup shell file for the
       ``expo.x.org:0''	display.

       DisplayManager.servers
	      This resource either  specifies  a  file	name  full  of	server
	      entries,	one  per line (if the value starts with	a slash), or a
	      single server entry.  See	the section Local Server Specification
	      for the details.

       DisplayManager.requestPort
	      This  indicates the UDP port number which	xdm uses to listen for
	      incoming XDMCP requests.	Unless you need	to debug  the  system,
	      leave this with its default value	of 177.

       DisplayManager.errorLogFile
	      Error output is normally directed	at the system console.	To re-
	      direct it, set this resource to a	file name.  A method  to  send
	      these  messages  to syslog should	be developed for systems which
	      support it; however, the wide variety  of	 interfaces  precludes
	      any  system-independent implementation.  This file also contains
	      any output directed to stderr by the Xsetup, Xstartup,  Xsession
	      and Xreset files,	so it will contain descriptions	of problems in
	      those scripts as well.

       DisplayManager.debugLevel
	      If the integer value of this  resource  is  greater  than	 zero,
	      reams  of	 debugging  information	will be	printed.  It also dis-
	      ables daemon mode, which would redirect the information into the
	      bit-bucket,  and	allows	non-root users to run xdm, which would
	      normally not be useful.

       DisplayManager.daemonMode
	      Normally,	xdm attempts to	make  itself  into  a  daemon  process
	      unassociated with	any terminal.  This is accomplished by forking
	      and leaving the  parent  process	to  exit,  then	 closing  file
	      descriptors  and	releasing  the	controlling terminal.  In some
	      environments this	is not desired	(in  particular,  when	debug-
	      ging).   Setting	this  resource	to ``false'' will disable this
	      feature.

       DisplayManager.pidFile
	      The filename specified will be created to	contain	an ASCII  rep-
	      resentation of the process-id of the main	xdm process.  Xdm also
	      uses file	locking	on this	file to	attempt	to eliminate  multiple
	      daemons  running	on the same machine, which would cause quite a
	      bit of havoc.

       DisplayManager.lockPidFile
	      This is the resource which controls whether xdm uses file	 lock-
	      ing  to  keep  multiple  display managers	from running amok.  On
	      System V,	this uses the lockf library call, while	on BSD it uses
	      flock.

       DisplayManager.authDir
	      This  names  a  directory	 under	which xdm stores authorization
	      files while initializing the  session.   The  default  value  is
	      /var/db/xdm.   Can  be  overridden for specific displays by Dis-
	      playManager.DISPLAY.authFile.

       DisplayManager.autoRescan
	      This boolean controls whether  xdm  rescans  the	configuration,
	      servers,	access	control	 and authentication keys files after a
	      session terminates and the files have changed.  By default it is
	      ``true.''	  You can force	xdm to reread these files by sending a
	      SIGHUP to	the main process.

       DisplayManager.removeDomainname
	      When computing the display name  for  XDMCP  clients,  the  name
	      resolver	will  typically	create a fully qualified host name for
	      the terminal.  As	this is	sometimes confusing, xdm  will	remove
	      the  domain  name	 portion of the	host name if it	is the same as
	      the domain name of the local host	when this variable is set.  By
	      default the value	is ``true.''

       DisplayManager.keyFile
	      XDM-AUTHENTICATION-1  style XDMCP	authentication requires	that a
	      private key be  shared  between  xdm  and	 the  terminal.	  This
	      resource specifies the file containing those values.  Each entry
	      in the file consists of a	display	name and the shared  key.   By
	      default,	xdm does not include support for XDM-AUTHENTICATION-1,
	      as it requires DES which is not generally	distributable  because
	      of United	States export restrictions.

       DisplayManager.accessFile
	      To prevent unauthorized XDMCP service and	to allow forwarding of
	      XDMCP IndirectQuery requests, this file contains a  database  of
	      hostnames	 which	are  either  allowed  direct  access  to  this
	      machine, or have a list of hosts to which	queries	should be for-
	      warded  to.  The format of this file is described	in the section
	      XDMCP Access Control.

       DisplayManager.exportList
	      A	list of	additional environment variables, separated  by	 white
	      space,  to pass on to the	Xsetup,	Xstartup, Xsession, and	Xreset
	      programs.

       DisplayManager.randomDevice
	      A	file to	read 8 bytes from to generate the seed	of  authoriza-
	      tion  keys.   The	default	is  /dev/urandom . If this file	cannot
	      be read, or if a read blocks for more than 5 seconds, xdm	 falls
	      back  to using a checksum	of DisplayManager.randomFile to	gener-
	      ate the seed.

       DisplayManager.greeterLib
	      On systems that support a	dynamically-loadable greeter  library,
	      the name of the library.	The default is
	       /usr/local/lib/X11/xdm/libXdmGreet.so.

       DisplayManager.choiceTimeout
	      Number  of seconds to wait for display to	respond	after user has
	      selected a host from the chooser.	 If the	display	sends an XDMCP
	      IndirectQuery  within this time, the request is forwarded	to the
	      chosen host.  Otherwise, it is assumed to	be from	a new  session
	      and the chooser is offered again.	 Default is 15.

       DisplayManager.sourceAddress
	      Use  the numeric IP address of the incoming connection on	multi-
	      homed hosts instead of the host name. This is to avoid trying to
	      connect on the wrong interface which might be down at this time.

       DisplayManager.willing
	      This specifies a program which is	run (as) root when an an XDMCP
	      BroadcastQuery is	received and this host is configured to	 offer
	      XDMCP display management.	The output of this program may be dis-
	      played on	a chooser window.  If no  program  is  specified,  the
	      string Willing to	manage is sent.

       DisplayManager.DISPLAY.resources
	      This  resource  specifies	 the  name of the file to be loaded by
	      xrdb as the resource database onto the root window of  screen  0
	      of  the  display.	  The  Xsetup  program,	 the Login widget, and
	      chooser will use the resources set in this file.	This  resource
	      data  base is loaded just	before the authentication procedure is
	      started, so it can control the appearance	of the	login  window.
	      See the section Authentication Widget, which describes the vari-
	      ous resources that are appropriate to place in this file.	 There
	      is no default value for this resource, but
	       /usr/local/lib/X11/xdm/Xresources is the	conventional name.

       DisplayManager.DISPLAY.chooser
	      Specifies	 the  program  run  to	offer a	host menu for Indirect
	      queries redirected to the	special	host name CHOOSER.
	       /usr/local/lib/X11/xdm/chooser  is the default.	See  the  sec-
	      tions XDMCP Access Control and Chooser.

       DisplayManager.DISPLAY.xrdb
	      Specifies	 the  program used to load the resources.  By default,
	      xdm uses	/usr/local/bin/xrdb.

       DisplayManager.DISPLAY.cpp
	      This specifies the name of the C preprocessor which is  used  by
	      xrdb.

       DisplayManager.DISPLAY.setup
	      This  specifies a	program	which is run (as root) before offering
	      the Login	window.	 This may be used to change the	appearance  of
	      the  screen  around  the Login window or to put up other windows
	      (e.g., you may want to run xconsole here).  By default, no  pro-
	      gram  is	run.   The  conventional  name for a file used here is
	      Xsetup.  See the section Setup Program.

       DisplayManager.DISPLAY.startup
	      This specifies a program	which  is  run	(as  root)  after  the
	      authentication process succeeds.	By default, no program is run.
	      The conventional name for	a file used here is Xstartup.  See the
	      section Startup Program.

       DisplayManager.DISPLAY.session
	      This specifies the session to be executed	(not running as	root).
	      By default,  /usr/local/bin/xterm	is run.	 The conventional name
	      is Xsession.  See	the section Session Program.

       DisplayManager.DISPLAY.reset
	      This  specifies  a program which is run (as root)	after the ses-
	      sion terminates.	By default, no program is  run.	  The  conven-
	      tional name is Xreset.  See the section Reset Program.

       DisplayManager.DISPLAY.openDelay

       DisplayManager.DISPLAY.openRepeat

       DisplayManager.DISPLAY.openTimeout

       DisplayManager.DISPLAY.startAttempts

       DisplayManager.DISPLAY.reservAttempts
	      These  numeric  resources	 control  the  behavior	 of  xdm  when
	      attempting to  open  intransigent	 servers.   openDelay  is  the
	      length  of  the  pause  in  seconds between successive attempts,
	      openRepeat is the	number of attempts to make, openTimeout	is the
	      amount of	time to	wait while actually attempting the open	(i.e.,
	      the maximum time spent in	the connect(2) system call) and	 star-
	      tAttempts	 is  the  number  of times this	entire process is done
	      before giving up on the server.  After openRepeat	attempts  have
	      been  made,  or  if openTimeout seconds elapse in	any particular
	      attempt, xdm terminates and restarts the server,	attempting  to
	      connect again.  This process is repeated startAttempts times, at
	      which point the display is declared dead and disabled.  Although
	      this behavior may	seem arbitrary,	it has been empirically	devel-
	      oped and works quite well	on most	systems.  The bound  reservAt-
	      tempts is	the number of times a successful connect is allowed to
	      be followed by a fatal error.  When reached, the display is dis-
	      abled.   The  default  values  are openDelay: 15,	openRepeat: 5,
	      openTimeout: 120,	startAttempts: 4 and reservAttempts: 2.

       DisplayManager.DISPLAY.pingInterval

       DisplayManager.DISPLAY.pingTimeout
	      To discover when remote  displays	 disappear,  xdm  occasionally
	      pings them, using	an X connection	and XSync calls.  pingInterval
	      specifies	the time (in minutes) between each ping	attempt, ping-
	      Timeout  specifies  the  maximum	amount of time (in minutes) to
	      wait for the terminal to respond to the request.	If the	termi-
	      nal  does	 not  respond, the session is declared dead and	termi-
	      nated.  By default, both are set to  5  minutes.	 If  you  fre-
	      quently  use X terminals which can become	isolated from the man-
	      aging host, you may wish to increase this	value.	The only worry
	      is  that	sessions will continue to exist	after the terminal has
	      been accidentally	disabled.  xdm will not	ping  local  displays.
	      Although it would	seem harmless, it is unpleasant	when the work-
	      station session is terminated as a result	of the server  hanging
	      for NFS service and not responding to the	ping.

       DisplayManager.DISPLAY.terminateServer
	      This  boolean  resource specifies	whether	the X server should be
	      terminated when a	session	terminates (instead of resetting  it).
	      This  option  can	 be used when the server tends to grow without
	      bound over time, in order	to limit the amount of time the	server
	      is run.  The default value is ``false.''

       DisplayManager.DISPLAY.userPath
	      Xdm  sets	 the PATH environment variable for the session to this
	      value.  It should	be a colon separated list of directories;  see
	      sh(1)   for   a	full   description.    The  default  value  is
	      ``/bin:/usr/bin:/sbin:/usr/sbin:/usr/local/bin:/usr/gnu/bin:/usr/local/bin''.

       DisplayManager.DISPLAY.systemPath
	      Xdm sets the PATH	environment variable for the startup and reset
	      scripts to the value of this resource.   The  default  for  this
	      resource	 is  ``/bin:/usr/bin:/sbin:/usr/sbin:/usr/local/bin''.
	      Note the absence of ``.''	from this entry.  This is a good prac-
	      tice to follow for root; it avoids many common Trojan Horse sys-
	      tem penetration schemes.

       DisplayManager.DISPLAY.systemShell
	      Xdm sets the SHELL environment  variable	for  the  startup  and
	      reset  scripts  to the value of this resource.  It is /bin/sh by
	      default.

       DisplayManager.DISPLAY.failsafeClient
	      If the default session fails to execute, xdm will	fall  back  to
	      this  program.   This program is executed	with no	arguments, but
	      executes using the same environment  variables  as  the  session
	      would  have  had (see the	section	Session	Program).  By default,
	      /usr/local/bin/xterm is used.

       DisplayManager.DISPLAY.grabServer

       DisplayManager.DISPLAY.grabTimeout
	      To improve security, xdm grabs the  server  and  keyboard	 while
	      reading  the  login  name	and password.  The grabServer resource
	      specifies	if the server should be	held for the duration  of  the
	      name/password  reading.  When ``false,'' the server is ungrabbed
	      after the	 keyboard  grab	 succeeds,  otherwise  the  server  is
	      grabbed  until  just  before the session begins.	The default is
	      ``false.''  The grabTimeout resource specifies the maximum  time
	      xdm  will	 wait  for  the	grab to	succeed.  The grab may fail if
	      some other client	has the	server grabbed,	 or  possibly  if  the
	      network  latencies  are  very high.  This	resource has a default
	      value of 3 seconds; you should be	cautious when raising it, as a
	      user  can	 be spoofed by a look-alike window on the display.  If
	      the grab fails, xdm kills	and restarts the server	(if  possible)
	      and the session.

       DisplayManager.DISPLAY.authorize

       DisplayManager.DISPLAY.authName
	      authorize	 is a boolean resource which controls whether xdm gen-
	      erates and uses authorization for	the local server  connections.
	      If  authorization	 is  used, authName is a list of authorization
	      mechanisms to use, separated by white space.  XDMCP  connections
	      dynamically  specify  which  authorization  mechanisms  are sup-
	      ported, so authName is ignored in	this case.  When authorize  is
	      set  for	a display and authorization is not available, the user
	      is informed by having a different	message	displayed in the login
	      widget.	By default, authorize is ``true,''  authName is	``MIT-
	      MAGIC-COOKIE-1,''	 or,  if  XDM-AUTHORIZATION-1  is   available,
	      ``XDM-AUTHORIZATION-1 MIT-MAGIC-COOKIE-1.''

       DisplayManager.DISPLAY.authFile
	      This file	is used	to communicate the authorization data from xdm
	      to the server, using the -auth server command line  option.   It
	      should  be kept in a directory which is not world-writable as it
	      could easily be removed, disabling the  authorization  mechanism
	      in  the server.  If not specified, a name	is generated from Dis-
	      playManager.authDir and the name of the display.

       DisplayManager.DISPLAY.authComplain
	      If set to	``false,'' disables the	use of the unsecureGreeting in
	      the  login  window.  See the section Authentication Widget.  The
	      default is ``true.''

       DisplayManager.DISPLAY.resetSignal
	      The number of the	signal xdm sends to reset the server.  See the
	      section Controlling the Server.  The default is 1	(SIGHUP).

       DisplayManager.DISPLAY.termSignal
	      The number of the	signal xdm sends to terminate the server.  See
	      the  section  Controlling	 the  Server.	The  default   is   15
	      (SIGTERM).

       DisplayManager.DISPLAY.resetForAuth
	      The  original  implementation  of	 authorization	in  the	sample
	      server reread the	 authorization	file  at  server  reset	 time,
	      instead  of when checking	the initial connection.	 As xdm	gener-
	      ates the authorization information just before connecting	to the
	      display,	an  old	 server	would not get up-to-date authorization
	      information.  This resource causes xdm to	 send  SIGHUP  to  the
	      server  after  setting up	the file, causing an additional	server
	      reset to occur, during which time	the new	authorization informa-
	      tion  will  be  read.  The default is ``false,'' which will work
	      for all MIT servers.

       DisplayManager.DISPLAY.userAuthDir
	      When xdm is unable to write to the usual user authorization file
	      ($HOME/.Xauthority),  it	creates	 a  unique  file  name in this
	      directory	and points the environment variable XAUTHORITY at  the
	      created file.  It	uses /tmp by default.

CONFIGURATION FILE
       First,  the  xdm	configuration file should be set up.  Make a directory
       (usually	 /usr/local/lib/X11/xdm) to contain all	of the relevant	files.

       Here is a reasonable configuration file,	which could be named  xdm-con-
       fig:

	    DisplayManager.servers:	       /usr/local/lib/X11/xdm/Xservers
	    DisplayManager.errorLogFile:       /var/log/xdm.log
	    DisplayManager*resources:	       /usr/local/lib/X11/xdm/Xresources
	    DisplayManager*startup:	       /usr/local/lib/X11/xdm/Xstartup
	    DisplayManager*session:	       /usr/local/lib/X11/xdm/Xsession
	    DisplayManager.pidFile:	       /var/run/xdm-pid
	    DisplayManager._0.authorize:       true
	    DisplayManager*authorize:	       false

       Note  that  this	 file mostly contains references to other files.  Note
       also that some of the resources are specified with ``*''	separating the
       components.  These resources can	be made	unique for each	different dis-
       play, by	replacing the ``*'' with the display-name, but	normally  this
       is  not	very useful.  See the Resources	section	for a complete discus-
       sion.

XDMCP ACCESS CONTROL
       The database file specified by the  DisplayManager.accessFile  provides
       information  which  xdm uses to control access from displays requesting
       XDMCP service.  This file contains three	 types	of  entries:   entries
       which  control  the  response  to Direct	and Broadcast queries, entries
       which control the response to Indirect queries, and macro definitions.

       The format of the Direct	entries	is simple, either a  host  name	 or  a
       pattern,	 which	is  distinguished from a host name by the inclusion of
       one or more meta	characters (`*'	matches	any  sequence  of  0  or  more
       characters,  and	 `?'  matches any single character) which are compared
       against the host	name of	the display device.  If	the entry  is  a  host
       name,  all  comparisons	are  done using	network	addresses, so any name
       which converts to the correct network address may be  used.   For  pat-
       terns,  only canonical host names are used in the comparison, so	ensure
       that you	do not attempt to match	aliases.  Preceding either a host name
       or  a  pattern with a `!' character causes hosts	which match that entry
       to be excluded.

       To only respond to Direct queries for a host or pattern,	it can be fol-
       lowed  by  the  optional	 ``NOBROADCAST'' keyword.  This	can be used to
       prevent an xdm server  from  appearing  on  menus  based	 on  Broadcast
       queries.

       An  Indirect entry also contains	a host name or pattern,	but follows it
       with a list of host names or macros to which indirect queries should be
       sent.

       A  macro	 definition contains a macro name and a	list of	host names and
       other macros that the macro expands to.	 To  distinguish  macros  from
       hostnames,  macro  names	 start	with  a	 `%' character.	 Macros	may be
       nested.

       Indirect	entries	may also specify to have xdm run chooser  to  offer  a
       menu of hosts to	connect	to.  See the section Chooser.

       When  checking  access  for  a  particular  display host, each entry is
       scanned in turn and the first matching entry determines	the  response.
       Direct  and Broadcast entries are ignored when scanning for an Indirect
       entry and vice-versa.

       Blank lines are ignored,	`#' is treated as a comment delimiter  causing
       the  rest of that line to be ignored, and `\newline' causes the newline
       to be ignored, allowing indirect	host lists to span multiple lines.

       Here is an example Xaccess file:

       #
       # Xaccess - XDMCP access	control	file
       #

       #
       # Direct/Broadcast query	entries
       #

       !xtra.lcs.mit.edu   # disallow direct/broadcast service for xtra
       bambi.ogi.edu	   # allow access from this particular display
       *.lcs.mit.edu	   # allow access from any display in LCS

       *.deshaw.com	   NOBROADCAST	       # allow only direct access
       *.gw.com				       # allow direct and broadcast

       #
       # Indirect query	entries
       #

       %HOSTS		   expo.lcs.mit.edu xenon.lcs.mit.edu \
			   excess.lcs.mit.edu kanga.lcs.mit.edu

       extract.lcs.mit.edu xenon.lcs.mit.edu   #force extract to contact xenon
       !xtra.lcs.mit.edu   dummy	       #disallow indirect access
       *.lcs.mit.edu	   %HOSTS	       #all others get to choose

       If compiled with	IPv6 support, multicast	address	 groups	 may  also  be
       included	 in the	list of	addresses indirect queries are set to.	Multi-
       cast addresses may be followed by  an  optional	/  character  and  hop
       count.  If  no hop count	is specified, the multicast hop	count defaults
       to 1, keeping the packet	on the local network. For  IPv4	 multicasting,
       the hop count is	used as	the TTL.

       Examples:

       rincewind.sample.net ff02::1		    #IPv6 Multicast to ff02::1
						    #with a hop	count of 1
       ponder.sample.net    CHOOSER 239.192.1.1/16  #Offer a menu of hosts
						    #who respond to IPv4 Multicast
						    # to 239.192.1.1 with a TTL	of 16

CHOOSER
       For X terminals that do not offer a host	menu for use with Broadcast or
       Indirect	queries, the chooser program can do this  for  them.   In  the
       Xaccess	file,  specify	``CHOOSER'' as the first entry in the Indirect
       host list.  Chooser will	send a Query request to	each of	the  remaining
       host names in the list and offer	a menu of all the hosts	that respond.

       The  list  may consist of the word ``BROADCAST,'' in which case chooser
       will send a Broadcast instead, again offering a menu of all hosts  that
       respond.	  Note	that  on some operating	systems, UDP packets cannot be
       broadcast, so this feature will not work.

       Example Xaccess file using chooser:

       extract.lcs.mit.edu  CHOOSER %HOSTS	    #offer a menu of these hosts
       xtra.lcs.mit.edu	    CHOOSER BROADCAST	    #offer a menu of all hosts

       The program to use for chooser is specified by the  DisplayManager.DIS-
       PLAY.chooser  resource.	For more flexibility at	this step, the chooser
       could be	a shell	script.	 Chooser is the	session	manager	 here;	it  is
       run instead of a	child xdm to manage the	display.

       Resources  for  this program can	be put into the	file named by Display-
       Manager.DISPLAY.resources.

       When the	user selects a host, chooser prints the	host chosen, which  is
       read  by	the parent xdm,	and exits.  xdm	closes its connection to the X
       server, and the server resets and sends another Indirect	XDMCP request.
       xdm  remembers the user's choice	(for DisplayManager.choiceTimeout sec-
       onds) and forwards the request to the chosen host, which	starts a  ses-
       sion on that display.

LISTEN
       The  following  configuration directive is also defined for the Xaccess
       configuration file:

       LISTEN interface	[list of multicast group addresses]
	      interface	may be a hostname or IP	address	representing a network
	      interface	 on  this  machine, or the wildcard * to represent all
	      available	network	interfaces.

       If one or more LISTEN lines are specified, xdm only listens  for	 XDMCP
       connections  on	the specified interfaces. If multicast group addresses
       are listed on a listen line, xdm	joins  the  multicast  groups  on  the
       given interface.

       If no LISTEN lines are given, the original behavior of listening	on all
       interfaces is preserved for backwards compatibility.  Additionally,  if
       no  LISTEN  is  specified,  xdm	joins the default XDMCP	IPv6 multicast
       group, when compiled with IPv6 support.

       To disable listening for	XDMCP connections altogther, a line of	LISTEN
       with  no	addresses may be specified, or the previously supported	method
       of setting DisplayManager.requestPort to	0 may be used.

       Examples:
       LISTEN *	ff02::1	   # Listen on all interfaces and to the
			   # ff02::1 IPv6 multicast group.
       LISTEN 10.11.12.13  # Listen only on this interface, as long
			   # as	no other listen	directives appear in
			   # file.

IPv6 MULTICAST ADDRESS SPECIFICATION
       The   Internet	Assigned   Numbers   Authority	 has   has    assigned
       ff0X:0:0:0:0:0:0:12b  as	 the  permanently  assigned range of multicast
       addresses for XDMCP. The	X in the prefix	may be replaced	by  any	 valid
       scope  identifier,  such	 as 1 for Interface-Local, 2 for Link-Local, 5
       for Site-Local, and so on.  (See	IETF RFC 4291 or its  replacement  for
       further	details	 and scope definitions.)  xdm defaults to listening on
       the Link-Local scope address ff02:0:0:0:0:0:0:12b to most closely match
       the old IPv4 subnet broadcast behavior.

LOCAL SERVER SPECIFICATION
       The resource DisplayManager.servers gives a server specification	or, if
       the values starts with a	slash (/),  the	 name  of  a  file  containing
       server specifications, one per line.

       Each  specification indicates a display which should constantly be man-
       aged and	which is not using XDMCP.  This	method is used	typically  for
       local  servers only.  If	the resource or	the file named by the resource
       is empty, xdm will offer	XDMCP service only.

       Each specification consists of at least three parts:  a display name, a
       display	class,	a display type,	and (for local servers)	a command line
       to start	the server.  A typical entry for local display number 0	 would
       be:

	 :0 Digital-QV local /usr/local/bin/X :0

       The display types are:

       local	 local display:	xdm must run the server
       foreign	 remote	display: xdm opens an X	connection to a	running	server

       The  display  name must be something that can be	passed in the -display
       option to an X program.	This string is used to generate	 the  display-
       specific	 resource  names,  so be careful to match the names (e.g., use
       ``:0 Sun-CG3 local /usr/local/bin/X :0''	instead	of ``localhost:0  Sun-
       CG3  local  /usr/local/bin/X :0'' if your other resources are specified
       as ``DisplayManager._0.session'').  The display class portion  is  also
       used  in	 the display-specific resources, as the	class of the resource.
       This is useful if you have a large collection of	similar	displays (such
       as  a corral of X terminals) and	would like to set resources for	groups
       of them.	 When using XDMCP, the display is required to specify the dis-
       play  class,  so	the manual for your particular X terminal should docu-
       ment the	display	class string for your device.  If it doesn't, you  can
       run  xdm	in debug mode and look at the resource strings which it	gener-
       ates for	that device, which will	include	the class string.

       When xdm	starts a session,  it  sets  up	 authorization	data  for  the
       server.	 For  local  servers,  xdm  passes  ``-auth  filename''	on the
       server's	command	line to	point it at its	authorization data.  For XDMCP
       servers,	xdm passes the authorization data to the server	via the	Accept
       XDMCP request.

RESOURCES FILE
       The Xresources file is loaded onto the display as a  resource  database
       using  xrdb.   As  the authentication widget reads this database	before
       starting	up, it usually contains	parameters for that widget:

	    xlogin*login.translations: #override\
		 Ctrl<Key>R: abort-display()\n\
		 <Key>F1: set-session-argument(failsafe) finish-field()\n\
		 <Key>Return: set-session-argument() finish-field()
	    xlogin*borderWidth:	3
	    xlogin*greeting: CLIENTHOST
	    #ifdef COLOR
	    xlogin*greetColor: CadetBlue
	    xlogin*failColor: red
	    #endif

       Please note the translations entry; it specifies	a few new translations
       for  the	 widget	 which	allow users to escape from the default session
       (and avoid troubles that	may occur in it).  Note	that if	 #override  is
       not specified, the default translations are removed and replaced	by the
       new value, not a	very useful result as some of the default translations
       are  quite  useful (such	as ``<Key>: insert-char	()'' which responds to
       normal typing).

       This file may also contain resources for	the setup program and chooser.

SETUP PROGRAM
       The Xsetup file is run after the	server is reset, but before the	 Login
       window is offered.  The file is typically a shell script.  It is	run as
       root, so	should be careful about	security.  This	is the place to	change
       the root	background or bring up other windows that should appear	on the
       screen along with the Login widget.

       In addition to any specified by DisplayManager.exportList, the  follow-
       ing environment variables are passed:

	    DISPLAY	   the associated display name
	    PATH	   the value of	DisplayManager.DISPLAY.systemPath
	    SHELL	   the value of	DisplayManager.DISPLAY.systemShell
	    XAUTHORITY	   may be set to an authority file

       Note  that  since xdm grabs the keyboard, any other windows will	not be
       able to receive keyboard	input.	They will be able to interact with the
       mouse,  however;	 beware	of potential security holes here.  If Display-
       Manager.DISPLAY.grabServer is set, Xsetup will not be able  to  connect
       to  the display at all.	Resources for this program can be put into the
       file named by DisplayManager.DISPLAY.resources.

       Here is a sample	Xsetup script:

	    #!/bin/sh
	    # Xsetup_0 - setup script for one workstation
	    xcmsdb < /usr/local/lib/X11/xdm/monitors/alex.0
	    xconsole -geometry 480x130-0-0 -notify -verbose -exitOnFail	&

AUTHENTICATION WIDGET
       The authentication widget prompts the user for the username,  password,
       and/or  other  required	authentication data from the keyboard.	Nearly
       every  imaginable  parameter  can  be  controlled  with	 a   resource.
       Resources for this widget should	be put into the	file named by Display-
       Manager.DISPLAY.resources.  All of these	have reasonable	 default  val-
       ues, so it is not necessary to specify any of them.

       The  resource  file  is loaded with xrdb(1) so it may use the substitu-
       tions defined by	that program such as CLIENTHOST	for the	 client	 host-
       name in the login message, or C pre-processor #ifdef statements to pro-
       duce different displays depending on color depth	or other variables.

       Xdm can be compiled with	support	for the	Xft(3) library for  font  ren-
       dering.	  If  this  support is present,	font faces are specified using
       the resources with names	ending in ``face'' in the fontconfig face for-
       mat described in	the Font Names section of fonts.conf(5).  If not, then
       fonts are specified using the resources with names ending  in  ``font''
       in  the	traditional X Logical Font Description format described	in the
       Font Names section of X(7).

       xlogin.Login.width, xlogin.Login.height,	xlogin.Login.x,	xlogin.Login.y
	      The geometry of the Login	widget is normally computed  automati-
	      cally.   If  you	wish to	position it elsewhere, specify each of
	      these resources.

       xlogin.Login.foreground
	      The color	used to	display	the input typed	by the user.

       xlogin.Login.face
	      The face used to display the input typed by the user when	 built
	      with Xft support.	 The default is	``Serif-18''.

       xlogin.Login.font
	      The  font	 used  to display the input typed by the user when not
	      built with Xft support.

       xlogin.Login.greeting
	      A	string which identifies	this window.  The default is ``X  Win-
	      dow System.''

       xlogin.Login.unsecureGreeting
	      When  X authorization is requested in the	configuration file for
	      this display and none is in  use,	 this  greeting	 replaces  the
	      standard	greeting.   The	 default is ``This is an unsecure ses-
	      sion''

       xlogin.Login.greetFace
	      The face used to display the greeting when built with  Xft  sup-
	      port.  The default is ``Serif-24:italic''.

       xlogin.Login.greetFont
	      The  font	 used  to display the greeting when not	built with Xft
	      support.

       xlogin.Login.greetColor
	      The color	used to	display	the greeting.

       xlogin.Login.namePrompt
	      The string displayed to prompt for a  user  name.	  Xrdb	strips
	      trailing	white  space from resource values, so to add spaces at
	      the end of the prompt (usually a nice thing), add	spaces escaped
	      with backslashes.	 The default is	``Login:  ''

       xlogin.Login.passwdPrompt
	      The string displayed to prompt for a password, when not using an
	      authentication system such as PAM	that provides its own prompts.
	      The default is ``Password:  ''

       xlogin.Login.promptFace
	      The  face	 used  to display prompts when built with Xft support.
	      The default is ``Serif-18:bold''.

       xlogin.Login.promptFont
	      The font used to display prompts when not	built  with  Xft  sup-
	      port.

       xlogin.Login.promptColor
	      The color	used to	display	prompts.

       xlogin.Login.changePasswdMessage
	      A	 message  which	 is  displayed	when  the  users  password has
	      expired.	The default is ``Password Change Required''

       xlogin.Login.fail
	      A	message	which is displayed when	the authentication fails, when
	      not using	an authentication system such as PAM that provides its
	      own prompts.  The	default	is ``Login incorrect''

       xlogin.Login.failFace
	      The face used to display the failure message when	built with Xft
	      support.	The default is ``Serif-18:bold''.

       xlogin.Login.failFont
	      The font used to display the failure message when	not built with
	      Xft support.

       xlogin.Login.failColor
	      The color	used to	display	the failure message.

       xlogin.Login.failTimeout
	      The number of seconds that the  failure  message	is  displayed.
	      The default is 10.

       xlogin.Login.logoFileName
	      Name  of	an XPM format pixmap to	display	in the greeter window,
	      if built with XPM	support.   The default is no pixmap.

       xlogin.Login.logoPadding
	      Number of	pixels of space	between	the logo pixmap	and other ele-
	      ments  of	 the  greeter window, if the pixmap is displayed.  The
	      default is 5.

       xlogin.Login.useShape
	      If set to	``true'', when built with XPM support, attempt to  use
	      the  X  Non-Rectangular Window Shape Extension to	set the	window
	      shape.  The default is ``true''.

       xlogin.Login.hiColor, xlogin.Login.shdColor
	      Raised appearance	bezels may be drawn around the	greeter	 frame
	      and text input boxes by setting these resources.	hiColor	is the
	      highlight	color, used on the top and left	sides  of  the	frame,
	      and  the	bottom and right sides of text input areas.   shdColor
	      is the shadow color, used	on the bottom and right	sides  of  the
	      frame,  and  the	top  and  left sides of	text input areas.  The
	      default for both is  the	foreground  color,  providing  a  flat
	      appearance.

       xlogin.Login.frameWidth
	      frameWidth is the	width in pixels	of the area around the greeter
	      frame drawn in hiColor and shdColor.

       xlogin.Login.innerFramesWidth
	      innerFramesWidth is the width in pixels of the area around  text
	      input areas drawn	in hiColor and shdColor.

       xlogin.Login.sepWidth
	      sepWidth	is the width in	pixels of the bezeled line between the
	      greeting and input areas drawn in	hiColor	and shdColor.

       xlogin.Login.allowRootLogin
	      If set to	``false'', don't allow root (and any other  user  with
	      uid  =  0)  to  log in directly.	The default is ``true''.  This
	      setting is only checked by some of the  authentication  backends
	      at this time.

       xlogin.Login.allowNullPasswd
	      If set to	``true'', allow	an otherwise failing password match to
	      succeed if the account does not require a	password at all.   The
	      default is ``false'', so only users that have passwords assigned
	      can log in.

       xlogin.Login.echoPasswd
	      If set to	``true'',  a  placeholder  character  (echoPasswdChar)
	      will be shown for	fields normally	set to not echo, such as pass-
	      word input.  The default is ``false''.

       xlogin.Login.echoPasswdChar
	      Character	to display if echoPasswd  is  true.   The  default  is
	      ``*''.   If  set	to an empty value, the cursor will advance for
	      each character input, but	no text	will be	drawn.

       xlogin.Login.translations
	      This specifies the  translations	used  for  the	login  widget.
	      Refer  to	 the X Toolkit documentation for a complete discussion
	      on translations.	The default translation	table is:

		   Ctrl<Key>H:	  delete-previous-character() \n\
		   Ctrl<Key>D:	  delete-character() \n\
		   Ctrl<Key>B:	  move-backward-character() \n\
		   Ctrl<Key>F:	  move-forward-character() \n\
		   Ctrl<Key>A:	  move-to-begining() \n\
		   Ctrl<Key>E:	  move-to-end()	\n\
		   Ctrl<Key>K:	  erase-to-end-of-line() \n\
		   Ctrl<Key>U:	  erase-line() \n\
		   Ctrl<Key>X:	  erase-line() \n\
		   Ctrl<Key>C:	  restart-session() \n\
		   Ctrl<Key>\\:	  abort-session() \n\
		   <Key>BackSpace:delete-previous-character() \n\
		   <Key>Delete:	  delete-previous-character() \n\
		   <Key>Return:	  finish-field() \n\
		   <Key>:	  insert-char()	\

       The actions which are supported by the widget are:

       delete-previous-character
	      Erases the character before the cursor.

       delete-character
	      Erases the character after the cursor.

       move-backward-character
	      Moves the	cursor backward.

       move-forward-character
	      Moves the	cursor forward.

       move-to-begining
	      (Apologies about the spelling error.)  Moves the cursor  to  the
	      beginning	of the editable	text.

       move-to-end
	      Moves the	cursor to the end of the editable text.

       erase-to-end-of-line
	      Erases all text after the	cursor.

       erase-line
	      Erases the entire	text.

       finish-field
	      If  the  cursor  is  in the name field, proceeds to the password
	      field; if	the cursor is in the password field, checks  the  cur-
	      rent  name/password  pair.   If the name/password	pair is	valid,
	      xdm starts the session.  Otherwise the failure message  is  dis-
	      played and the user is prompted again.

       abort-session
	      Terminates and restarts the server.

       abort-display
	      Terminates  the server, disabling	it.  This action is not	acces-
	      sible in the default configuration.  There are  various  reasons
	      to  stop xdm on a	system console,	such as	when shutting the sys-
	      tem down,	when using xdmshell, to	start another type of  server,
	      or  to  generally	access the console.  Sending xdm a SIGHUP will
	      restart the display.  See	the section Controlling	XDM.

       restart-session
	      Resets the X server and starts a new session.  This can be  used
	      when  the	 resources have	been changed and you want to test them
	      or when the screen has been overwritten with system messages.

       insert-char
	      Inserts the character typed.

       set-session-argument
	      Specifies	a single word argument which is	passed to the  session
	      at startup.  See the section Session Program.

       allow-all-access
	      Disables	access	control	 in the	server.	 This can be used when
	      the .Xauthority file cannot be created by	xdm.  Be very  careful
	      using  this;  it	might be better	to disconnect the machine from
	      the network before doing this.

       On  some	 systems  (OpenBSD)  the  user's  shell	 must  be  listed   in
       /etc/shells to allow login through xdm. The normal password and account
       expiration dates	are enforced too.

STARTUP	PROGRAM
       The Xstartup program is run as root when	the user logs in.  It is typi-
       cally a shell script.  Since it is run as root, Xstartup	should be very
       careful about security.	This is	the place to put  commands  which  add
       entries	to  utmp  or  wtmp  files,  (the sessreg program may be	useful
       here), mount users' home	directories from file servers,	or  abort  the
       session if logins are not allowed.

       In  addition to any specified by	DisplayManager.exportList, the follow-
       ing environment variables are passed:

	    DISPLAY	   the associated display name
	    HOME	   the initial working directory of the	user
	    LOGNAME	   the user name
	    USER	   the user name
	    PATH	   the value of	DisplayManager.DISPLAY.systemPath
	    SHELL	   the value of	DisplayManager.DISPLAY.systemShell
	    XAUTHORITY	   may be set to an authority file
	    WINDOWPATH	   may be set to the "window path" leading to the X server

       No arguments are	passed to the script.  Xdm  waits  until  this	script
       exits  before  starting	the  user  session.  If	the exit value of this
       script is non-zero, xdm discontinues the	 session  and  starts  another
       authentication cycle.

       The  sample  Xstartup  file  shown  here	 prevents login	while the file
       /etc/nologin exists.  Thus this is not a	complete example, but simply a
       demonstration of	the available functionality.

       Here is a sample	Xstartup script:

	    #!/bin/sh
	    #
	    # Xstartup
	    #
	    # This program is run as root after	the user is verified
	    #
	    if [ -f /etc/nologin ]; then
		 xmessage -file	/etc/nologin -timeout 30 -center
		 exit 1
	    fi
	    sessreg -a -l $DISPLAY -x /usr/local/lib/X11/xdm/Xservers $LOGNAME
	    /usr/local/lib/X11/xdm/GiveConsole
	    exit 0

SESSION	PROGRAM
       The Xsession program is the command which is run	as the user's session.
       It is run with the permissions of the authorized	user.

       In addition to any specified by DisplayManager.exportList, the  follow-
       ing environment variables are passed:

	    DISPLAY	   the associated display name
	    HOME	   the initial working directory of the	user
	    LOGNAME	   the user name
	    USER	   the user name
	    PATH	   the value of	DisplayManager.DISPLAY.userPath
	    SHELL	   the user's default shell (from getpwnam)
	    XAUTHORITY	   may be set to a non-standard	authority file
	    KRB5CCNAME	   may be set to a Kerberos credentials	cache name
	    WINDOWPATH	   may be set to the "window path" leading to the X server

       At  most	installations, Xsession	should look in $HOME for a file	.xses-
       sion, which contains commands that each user would like	to  use	 as  a
       session.	 Xsession should also implement	a system default session if no
       user-specified session exists.

       An argument may be passed to this program from the authentication  wid-
       get  using  the	`set-session-argument'	action.	  This	can be used to
       select different	styles of session.  One	good use of this feature is to
       allow the user to escape	from the ordinary session when it fails.  This
       allows users to repair their own	.xsession if it	fails, without requir-
       ing  administrative  intervention.   The	example	following demonstrates
       this feature.

       This example recognizes the special ``failsafe''	mode, specified	in the
       translations  in	 the  Xresources  file,	 to provide an escape from the
       ordinary	session.  It also requires that	the  .xsession	file  be  exe-
       cutable so we don't have	to guess what shell it wants to	use.

	    #!/bin/sh
	    #
	    # Xsession
	    #
	    # This is the program that is run as the client
	    # for the display manager.

	    case $# in
	    1)
		 case $1 in
		 failsafe)
		      exec xterm -geometry 80x24-0-0
		      ;;
		 esac
	    esac

	    startup=$HOME/.xsession
	    resources=$HOME/.Xresources

	    if [ -f "$startup" ]; then
		 exec "$startup"
	    else
		 if [ -f "$resources" ]; then
		      xrdb -load "$resources"
		 fi
		 twm &
		 xman -geometry	+10-10 &
		 exec xterm -geometry 80x24+10+10 -ls
	    fi

       The  user's  .xsession  file  might  look  something like this example.
       Don't forget that the file must have execute permission.
	    #! /bin/csh
	    # no -f in the previous line so .cshrc gets	run to set $PATH
	    twm	&
	    xrdb -merge	"$HOME/.Xresources"
	    emacs -geometry +0+50 &
	    xbiff -geometry -430+5 &
	    xterm -geometry -0+50 -ls

RESET PROGRAM
       Symmetrical with	Xstartup, the Xreset script is run after the user ses-
       sion has	terminated.  Run as root, it should contain commands that undo
       the effects of commands in Xstartup, updating entries in	utmp  or  wtmp
       files,  or  unmounting  directories from	file servers.  The environment
       variables that were passed to Xstartup are also passed to Xreset.

       A sample	Xreset script:
	    #!/bin/sh
	    #
	    # Xreset
	    #
	    # This program is run as root after	the session ends
	    #
	    sessreg -d -l $DISPLAY -x /usr/local/lib/X11/xdm/Xservers $LOGNAME
	    /usr/local/lib/X11/xdm/TakeConsole
	    exit 0

CONTROLLING THE	SERVER
       Xdm controls local servers using	POSIX signals.	SIGHUP is expected  to
       reset  the  server, closing all client connections and performing other
       cleanup duties.	SIGTERM	is expected to terminate the server.  If these
       signals	do not perform the expected actions, the resources DisplayMan-
       ager.DISPLAY.resetSignal	 and   DisplayManager.DISPLAY.termSignal   can
       specify alternate signals.

       To  control  remote  terminals not using	XDMCP, xdm searches the	window
       hierarchy on the	display	and uses the protocol request KillClient in an
       attempt	to  clean  up the terminal for the next	session.  This may not
       actually	kill all of the	clients, as only those which have created win-
       dows  will  be noticed.	XDMCP provides a more sure mechanism; when xdm
       closes its initial connection, the session is over and the terminal  is
       required	to close all other connections.

CONTROLLING XDM
       Xdm  responds  to two signals: SIGHUP and SIGTERM.  When	sent a SIGHUP,
       xdm rereads the configuration file, the access control  file,  and  the
       servers	file.	For  the servers file, it notices if entries have been
       added or	removed.  If a new entry has been added, xdm starts a  session
       on  the	associated  display.  Entries which have been removed are dis-
       abled immediately, meaning that any session in progress will be	termi-
       nated without notice and	no new session will be started.

       When sent a SIGTERM, xdm	terminates all sessions	in progress and	exits.
       This can	be used	when shutting down the system.

       Xdm attempts to mark its	various	sub-processes for ps(1)	by editing the
       command	line argument list in place.  Because xdm can't	allocate addi-
       tional space for	this task, it is useful	to start xdm with a reasonably
       long  command  line  (using the full path name should be	enough).  Each
       process which is	servicing a display is marked -display.

ADDITIONAL LOCAL DISPLAYS
       To add an additional local display, add a line for it to	 the  Xservers
       file.  (See the section Local Server Specification.)

       Examine the display-specific resources in xdm-config (e.g., DisplayMan-
       ager._0.authorize) and consider which of	them should be copied for  the
       new  display.  The default xdm-config has all the appropriate lines for
       displays	:0 and :1.

OTHER POSSIBILITIES
       You can use xdm to run a	single session at a time, using	the  4.3  init
       options	or  other suitable daemon by specifying	the server on the com-
       mand line:

	    xdm	-server	":0 SUN-3/60CG4	local /usr/local/bin/X :0"

       Or, you might have a file server	and a collection of X terminals.   The
       configuration  for  this	 is  identical to the sample above, except the
       Xservers	file would look	like

	    extol:0 VISUAL-19 foreign
	    exalt:0 NCD-19 foreign
	    explode:0 NCR-TOWERVIEW3000	foreign

       This directs xdm	to manage sessions on all three	 of  these  terminals.
       See  the	 section Controlling Xdm for a description of using signals to
       enable and disable these	terminals in a manner reminiscent of init(8).

LIMITATIONS
       One thing that xdm isn't	very good at doing is  coexisting  with	 other
       window  systems.	  To use multiple window systems on the	same hardware,
       you'll probably be more interested in xinit.

FILES
       /usr/local/lib/X11/xdm/xdm-config
			   the default configuration file

       $HOME/.Xauthority   user	authorization file where xdm stores  keys  for
			   clients to read

       /usr/local/lib/X11/xdm/chooser
			   the default chooser

       /usr/local/bin/xrdb the default resource	database loader

       /usr/local/bin/X	   the default server

       /usr/local/bin/xterm
			   the default session program and failsafe client

       /var/db/xdm/A_display_-_suffix_
			   the default place for authorization files

       /tmp/K5C_display_   Kerberos credentials	cache

SEE ALSO
       X(7),	xinit(1),   xauth(1),	xrdb(1),   Xsecurity(7),   sessreg(1),
       Xserver(1), xdmshell(1),	fonts.conf(5).
       X Display Manager Control Protocol
       IETF RFC	4291: IP Version 6 Addressing Architecture.

AUTHOR
       Keith Packard, MIT X Consortium

X Version 11			  xdm 1.1.11				XDM(1)

NAME | SYNOPSIS | DESCRIPTION | OVERVIEW | OPTIONS | RESOURCES | CONFIGURATION FILE | XDMCP ACCESS CONTROL | CHOOSER | LISTEN | IPv6 MULTICAST ADDRESS SPECIFICATION | LOCAL SERVER SPECIFICATION | RESOURCES FILE | SETUP PROGRAM | AUTHENTICATION WIDGET | STARTUP PROGRAM | SESSION PROGRAM | RESET PROGRAM | CONTROLLING THE SERVER | CONTROLLING XDM | ADDITIONAL LOCAL DISPLAYS | OTHER POSSIBILITIES | LIMITATIONS | FILES | SEE ALSO | AUTHOR

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=xdm&manpath=FreeBSD+12.0-RELEASE+and+Ports>

home | help