XHOST(1)                       X Version 11                        XHOST(1)

                                  Release 4



 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.  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).




 Hewlett-Packard Company            - 1 -        X11 Release 4 November 1991

 XHOST(1)                       X Version 11                        XHOST(1)

                                  Release 4



      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).

 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).

























 Hewlett-Packard Company            - 2 -        X11 Release 4 November 1991