XHOST(1) X Version 11 (Release 6.6) XHOST(1)
NAME
xhost - server access control program for X
SYNOPSIS
xhost [[+-]hostname ...]
DESCRIPTION
The xhost program is used to add and delete host names to
the list allowed to make connections to the X server. 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.
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.
[+]hostname
The given hostname (the plus sign is optional) is
added to the list allowed to connect to the X
server.
-hostname
The given hostname is removed from the list of
allowed to connect to the server. 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 every hostname, even if they
aren't on the list (i.e., access control is turned
off).
- Access is restricted to only those on the list
(i.e., 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
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XHOST(1) X Version 11 (Release 6.6) XHOST(1)
of those allowed to connect. This is the only
option that may be used from machines other than the
controlling host.
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 hostname added to the access control list, a line
of the form "hostname being added to access control list" is
printed. For each hostname removed from the access control
list, a line of the form "hostname being removed from access
control list" is printed.
FILES
/etc/X*.hosts
SEE ALSO
X(1), Xsecurity(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).
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.
AUTHORS
Bob Scheifler, MIT Laboratory for Computer Science,
Jim Gettys, MIT Project Athena (DEC).
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