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.
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.
[+ ]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 (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 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.
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.
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.
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).