XHOST(1)                                                                                                                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 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 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 cur-
               rent 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.

       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.

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 1.0.4                                                  XHOST(1)