xhost - server access control program for X
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.
Prints a usage message.
(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.
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).
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.
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.
A complete name has the syntax ``family:name'' where the families are as follows: Internet host DECnet host Secure RPC network name Kerberos V5 principal 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
that contain an at-sign (@) are assumed to be in the nis family. Otherwise,
the inet family is assumed.
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.
to get the default host and display to use.
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,
must be used to add the new address
and/or remove the old address.
Bob Scheifler, MIT Laboratory for Computer Science, Jim Gettys, MIT Project Athena (DEC).