xhost(1X) xhost(1X)
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. 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 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.
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) environ-
ment, 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 connec-
tions.
NAMES
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 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
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).
xhost(1X)