X Version 11 (Release 6.1)

xhost(X1M)

xhost -- server access control program for X

Synopsis

xhost [[+-]name . . .]

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.

Options

xhost accepts the following command line options described below. For security, the options that affect 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

displays the usegae messgae for xhost.

[+] name

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.

-name

name is removed from the list of allowed to connect to the server. The name can be a host name. Existing connections are not %broken, but new connection attempts will be denied.

NOTE: 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 all hosts, even if those not on the list (that is, access control is turned off).

-

Access is restricted to only those hosts on the list (that is, 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 clients 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 (for example, ``nis:unix.uid@domainname'') can be specified, or a local user can be specified with just the username and a trailing at-sign (for example, ``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.

Environment variables

DISPLAY: default host and display number

Files

/etc/X.hosts

Diagnostics

For each name added to the access control list, a line of the following form is printed.

   name being added to access control list

For each name removed from the access control list, a line of the following form is printed:

   name being removed from access control list

Warnings

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).

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.

References

xauth(X1M), Xsco(X1M), Xsecurity(X1M), X(X1M)