xhost(X)                      06 January 1993                       xhost(X)


 Name

    xhost - server access control program for X

 Syntax


    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.

 Options

    xhost accepts the following command line options described below.  For
    security, the options that affect 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  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     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  The current machine is allowed to be removed; how-
                 ever, 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 all users, even if those not on the list
              (that is, access control is turned off).

    -         access is restricted to only those on the list (that is, 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 clients allowed to connect.  This is
              the only option that may be used from machines other than the
              controlling host.


 Files

    /etc/X*.hosts

 Environment


    DISPLAY   default host and display number


 Diagnostics

    For each name added to the access control list, a line of the following
    form is printed.

       name being added to access control list

    For each name removed from the access control list, a line of the follow-
    ing form is printed:

       name being removed from access control list


 Known limitations

    You cannot specify a display on the command line because -display is a
    valid command line argument (indicating that you want to remove the ma-
    chine 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.

 See also

    xauth(X), Xsco(X), X(X)