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.
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.
Prints a usage message.
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.
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
Access is restricted to only those on the list (i.e., 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.
A complete name has the syntax "family:name" where the families are as
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.
When Secure RPC is being used, the network independent netname (e.g., "nis:unix.uid@domainname")
can be specified, or a local user can be specified with just the username 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 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.
X(1), Xsecurity(1), Xserver(1), xdm(1)
to get the default host and display to use.
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.
Bob Scheifler, MIT Laboratory for Computer Science, Jim Gettys, MIT
Project Athena (DEC).