XHOST(1)                        X11 5.4R3.00                        XHOST(1)


NAME
       xhost - server access control program for X

SYNOPSIS
       xhost [[+-]name ...]

DESCRIPTION
       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
       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 implement the user-
       based mechanism, or use the hooks in the protocol for passing other
       authentication data to the server.

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

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

OPTIONS
       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.

       [+]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
               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 (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



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XHOST(1)                        X11 5.4R3.00                        XHOST(1)


               than the controlling host.

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

FILES
       /etc/X*.hosts

SEE ALSO
       X(1), Xserver(1), xdm(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).

       This is not really a bug, but the X server stores network addresses,
       not host names.  If somehow you change a host's network address while
       the server is still running, xhost must be used to add the new
       address and/or remove the old address.

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).























Licensed material--property of copyright holder(s)                         2