XHOST(1)            X Version 11 (Release 4)             XHOST(1)



  NAME
       xhost - server access control program for X


  SYNOPSIS
       xhost [[+-]hostname ...]

  DESCRIPTION
       The xhost program is used to add and delete hosts to the
       list of machines that are allowed to make connections to the
       X server.  This provides a rudimentary form of privacy
       control and security.  It is only sufficient for a
       workstation (single user) environment, although it does
       limit the worst abuses.  Environments which require more
       sophisticated measures should use the hooks in the protocol
       for passing authentication data to the server.

       The server initially allows network connections only from
       programs running on the same machine or from machines listed
       in the file /etc/X*.hosts (where * is the display number of
       the server).  The xhost program is usually run either from a
       startup file or interactively to give access to other users.

       Hostnames that are followed by two colons (::) are used in
       checking DECnet connections; all other hostnames are used
       for TCP/IP connections.

  OPTIONS
       Xhost accepts the following command line options described
       below.  For security, the options that effect access control
       may only be run from the same machine as the server.

       [+]hostname
               The given hostname (the plus sign is optional) is
               added to the list of machines that are allowed to
               connect to the X server.

       -hostname
               The given hostname is removed from the list of
               machines that are allowed to connect to the server.


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               Existing connections are not broken, but new
               connection attempts will be denied.  Note that the
               current machine is allowed 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 of allowed hosts (i.e. access control is
               turned off).

       -       Access is restricted to only those machines on the
               list of allowed hosts (i.e. access control is turned
               on).

       nothing If no command line arguments are given, the list of
               hosts that are allowed to connect is printed on the
               standard output along with a message indicating
               whether or not access control is currently enabled.
               This is the only option that may be used from
               machines other than the one on which the server is
               running.

  FILES
       /etc/X*.hosts

  SEE ALSO
       X(1), Xserver(1)

  ENVIRONMENT
       DISPLAY to get the default host and display to use.

  BUGS
       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 machine named ``display'' from the
       access list).




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  COPYRIGHT
       Copyright 1988, Massachusetts Institute of Technology.
       See X(1) for a full statement of rights and permissions.

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



































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