XHOST(1)                       AIX                       XHOST(1)



     NAME
          xhost - server access control program for X

     SYNOPSIS
          xxxxhhhhoooosssstttt [[+-]name ...]

     DESCRIPTION
          The _x_h_o_s_t 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._u_i_d@_d_o_m_a_i_n_n_a_m_e") can be specified, or a local user can
          be specified with just the username and a trailing at-sign
          (e.g., "joe@").

     OPTIONS
          _X_h_o_s_t 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 worksta-
          tions, this is the same machine as the server.  For X termi-
          nals, it is the login host.

          [[[[++++]]]]_n_a_m_e The given _n_a_m_e (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.

          ----_n_a_m_e   The given _n_a_m_e 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 connec-
                  tions) 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


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     XHOST(1)                       AIX                       XHOST(1)



                  (i.e., access control is turned on).

          _n_o_t_h_i_n_g 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
                  controlling host.

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

     FILES
          /etc/X*.hosts

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

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

     BUGS
          You can't specify a display on the command line because
          ----ddddiiiissssppppllllaaaayyyy is a valid command line argument (indicating that
          you want to remove the machine named ``_d_i_s_p_l_a_y'' 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, _x_h_o_s_t
          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).











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