xhost - Online in the Cloud

PROGRAM:

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 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 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 complete name (See NAMES for
more details).

-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 complete name (See NAMES for more details). 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 (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
si Server Interpreted

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 they are assumed to be Internet addresses. If
compiled 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.

The local family specifies all the local connections at once. However, the server
interpreted address "si:localuser:username" can be used to specify a single local user.
(See the Xsecurity(7) manual page for more details.)

Server interpreted addresses consist of a case-sensitive type tag and a string
representing a given value, separated by a colon. For example, "si:hostname:almas" is a
server interpreted address of type hostname, with a value of almas. For more information
on the available forms of server interpreted addresses, see the Xsecurity(7) manual page.

The initial access control list for display number n may be set by the file /etc/Xn.hosts,
where n is the display number of the server. See Xserver(1) for details.

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.

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