Manual: xhost

XHOST(1)					   General Commands 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 suffi‐
       cient for a workstation (single user) environment, although it does limit the worst abuses.  Environments  which	 re‐
       quire  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	con‐
       trol  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 at‐
	       tempts 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 con‐
	       nections) 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	 en‐
	       abled 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:lo‐
       caluser: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 al‐
       mas.   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 con‐
       trol list" is printed.

SEE ALSO
       X(7), Xsecurity(7), Xserver(1), xdm(1), xauth(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, unless you use the server-interpreted hostname type address.
       If somehow you change a host's network address while the server is still running, and you are using a network-address
       based form of authentication, 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).

X Version 11						 xhost 1.0.9						    XHOST(1)