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xhost(1X)
X11R6
NAME
  xhost - server access control program for X

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

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.

  -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 are 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 those allowed to connect. This is the only option that may be
      used from machines other than the controlling host.

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.

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

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

FILES
  /etc/X*.hosts

BUGS
  You cannot 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.

SEE ALSO
  X(1X), Xsecurity(1X), Xdec(1X), xdm(1X)

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

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