XHOST(1) UNIX Programmer's Manual 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 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 worksta-
tions, this is the same machine as the server. For X termi-
nals, 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 connec-
tions) 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
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controlling host.
NAMES
A complete name has the syntax ``family:name'' where the
families are as follows:
inet Internet host (IPv4)
inet6 Internet host (IPv6)
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 net-
name (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 they are assumed to be Internet addresses. If com-
piled to support IPv6, then all IPv4 and IPv6 addresses
returned by getaddrinfo(3) are added to the access list in
the appropriate inet or inet6 family.
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(7), Xsecurity(7), Xserver(1), xdm(1), getaddrinfo(3)
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
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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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