XHOST(1)            RISC/os Reference Manual             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 con-
     trol and security.  It is only sufficient for a workstation
     (single user) environment, although it does limit the worst
     abuses.  Environments which require more sophisticated meas-
     ures 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 connec-
             tion 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



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XHOST(1)            RISC/os Reference Manual             XHOST(1)



             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).

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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