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CentOS 7.0 - man page for xhost (centos section 1)

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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 work-
       stations, 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  con-
	       trol 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  inter-
       preted  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  represent-
       ing  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-inter-
       preted  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 1.0.5					 XHOST(1)
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