XHOST(1) 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.
Hostnames that are followed by two colons (::) are used in
checking DECnet connections; all other hostnames are used
for TCP/IP connections.
User names contain an at-sign (@). When Secure RPC is
being used, the network independent netname (e.g.,
"unix.uid@domainname") can be specified, or a local user
can be specified with just the username and a trailing at-
sign (e.g., "joe@").
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.
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
X Version 11 Release 5 1
XHOST(1) XHOST(1)
(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.
DIAGNOSTICS
For each name added to the access control list, a line of
the form "name being added to access contro list" is
printed. For each name removed from the access control
list, a line of the form "name being removed from access
contro list" is printed.
FILES
/etc/X*.hosts
SEE ALSO
X(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).
This is not really a bug, but the X server stores network
addresses, not host names. 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.
COPYRIGHT
Copyright 1988, Massachusetts Institute of Technology.
See X(1) for a full statement of rights and permissions.
AUTHORS
Bob Scheifler, MIT Laboratory for Computer Science,
Jim Gettys, MIT Project Athena (DEC).
X Version 11 Release 5 2