xhost(1X)xhost(1X)NAMExhost - server access control program for X
SYNOPSISxhost [[+-]name...]
OPTIONSxhost 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; how‐
ever, 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 control‐
ling 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 secu‐
rity. 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 authenti‐
cation 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 con‐
tain 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 ALSOX(1X), Xsecurity(1X), Xdec(1X), xdm(1X)AUTHORS
Bob Scheifler, MIT Laboratory for Computer Science,
Jim Gettys, MIT Project Athena (DEC).
xhost(1X)
