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 rudimen-
       tary 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 effect access  con-
       trol  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.

       -help   Prints a usage message.

       [+]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 cur-
               rently 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 con-
               trolling host.

NAMES
       A  complete  name has the syntax ``family:name'' where the
       families are as follows:

       inet      Internet host
       dnet      DECnet host
       nis       Secure RPC network name
       krb       Kerberos V5 principal
       local     contains only one name, the empty string

       The family is case insensitive.  The format  of  the  name
       varies with the family.

       When  Secure  RPC  is  being used, the network independent
       netname uid@domainname"">e.g., "nis:unix.uid@domainname"  can  be  speci-
       fied, or a local user can be specified with just the user-
       name and a trailing at-sign e.g., "nis:pat@".

       For backward compatibility with pre-R6 xhost,  names  that
       contain  an  at-sign (@) are assumed to be in the nis fam-
       ily.  Otherwise the inet family is assumed.

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

FILES
       /etc/X*.hosts

SEE ALSO
       X(1) Xsecurity(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).

       The  X  server  stores  network addresses, not host names.
       This is not really a bug.  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.

AUTHORS
       Bob Scheifler, MIT Laboratory for Computer Science,
       Jim Gettys, MIT Project Athena (DEC).