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XHOST(1)		    General Commands Manual		      XHOST(1)

       xhost - server access control program for X

       xhost [[+-]name ...]

       The xhost program is used to add	and delete host	names or user names to
       the list	allowed	to make	connections to the X server.  In the  case  of
       hosts,  this  provides  a rudimentary form of privacy control and secu-
       rity.  It is only sufficient for	a workstation (single  user)  environ-
       ment,  although it does limit the worst abuses.	Environments which re-
       quire more sophisticated	measures should	implement the user-based mech-
       anism or	use the	hooks in the protocol for passing other	authentication
       data to the server.

       Xhost accepts the following command line	options	described below.   For
       security,  the  options that effect access control may only be run from
       the "controlling	host".	For workstations, this is the same machine  as
       the server.  For	X terminals, it	is the login host.

       -help   Prints a	usage message.

       [+]name The given name (the plus	sign is	optional) is added to the list
	       allowed to connect to the X server.  The	name  can  be  a  host
	       name or a user name.

       -name   The  given  name	is removed from	the list of allowed to connect
	       to the server.  The name	can be a host name  or	a  user	 name.
	       Existing	 connections  are  not	broken,	but new	connection at-
	       tempts will be denied.  Note that the current  machine  is  al-
	       lowed  to  be  removed; however,	further	connections (including
	       attempts	to add it back)	will not be permitted.	Resetting  the
	       server  (thereby	 breaking  all connections) is the only	way to
	       allow local connections again.

       +       Access is granted to everyone, even if they aren't on the  list
	       (i.e., access control is	turned off).

       -       Access  is  restricted  to only those on	the list (i.e.,	access
	       control is turned on).

       nothing If no command line arguments are	given,	a  message  indicating
	       whether	or not access control is currently enabled is printed,
	       followed	by the list of those allowed to	connect.  This is  the
	       only  option that may be	used from machines other than the con-
	       trolling	host.

       A complete name has the syntax ``family:name'' where the	 families  are
       as follows:

       inet	 Internet host (IPv4)
       inet6	 Internet host (IPv6)
       dnet	 DECnet	host
       nis	 Secure	RPC network name
       krb	 Kerberos V5 principal
       local	 contains only one name, the empty string
       si	 Server	Interpreted

       The family is case insensitive.	The format of the name varies with the

       When Secure RPC is being	used, the network independent  netname	(e.g.,
       "nis:unix.uid@domainname")  can	be  specified,	or a local user	can be
       specified  with	just  the  username  and  a  trailing  at-sign	(e.g.,

       For backward compatibility with pre-R6 xhost, names that	contain	an at-
       sign (@)	are assumed to be in the nis family.  Otherwise	they  are  as-
       sumed  to  be Internet addresses. If compiled to	support	IPv6, then all
       IPv4 and	IPv6 addresses returned	by getaddrinfo(3) are added to the ac-
       cess list in the	appropriate inet or inet6 family.

       Server interpreted addresses consist of a case-sensitive	type tag and a
       string representing a given value, separated by a colon.	 For  example,
       "si:hostname:almas"  is	a server interpreted address of	type hostname,
       with a value of almas.

       For each	name added to the access control list,	a  line	 of  the  form
       "name  being  added  to access control list" is printed.	 For each name
       removed from the	access control list, a line of the  form  "name	 being
       removed from access control list" is printed.


       X(7), Xsecurity(7), Xserver(1), xdm(1), xauth(1), getaddrinfo(3)

       DISPLAY to get the default host and display to use.

       You  can't  specify a display on	the command line because -display is a
       valid command line argument (indicating that you	want to	remove the ma-
       chine named ``display'' from the	access list).

       The  X  server stores network addresses,	not host names,	unless you use
       the server-interpreted hostname type address.  If somehow you change  a
       host's  network	address	while the server is still running, and you are
       using a network-address based form of  authentication,  xhost  must  be
       used to add the new address and/or remove the old address.

       Bob Scheifler, MIT Laboratory for Computer Science,
       Jim Gettys, MIT Project Athena (DEC).



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