NAME

xhost - server access control program for X

SYNOPSIS

xhost [[+-]hostname ...]

DESCRIPTION

The xhost program is used to add and delete hosts to the list of machines that are allowed to make connections to the X server.  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 use the hooks in the protocol for passing authentication data to the server. 

The server initially allows network connections only from programs running on the same machine or from machines listed in the file /etc/X∗.hosts (where ∗ is the display number of the server).  The xhost program is usually run either from a startup file or interactively to give access to other users. 

Hostnames that are followed by two colons (::) are used in checking DECnet connections; all other hostnames are used for TCP/IP connections. 

OPTIONS

Xhost accepts the following command line options described below.  For security, the options that effect access control may only be run from the same machine as the server. 

[+]hostname
The given hostname (the plus sign is optional) is added to the list of machines that are allowed to connect to the X server. 

−hostname
The given hostname is removed from the list of machines that are allowed to connect to the server.  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 of allowed hosts (i.e. access control is turned off). 

− Access is restricted to only those machines on the list of allowed hosts (i.e. access control is turned on). 

nothing If no command line arguments are given, the list of hosts that are allowed to connect is printed on the standard output along with a message indicating whether or not access control is currently enabled.  This is the only option that may be used from machines other than the one on which the server is running. 

FILES

/etc/X∗.hosts

SEE ALSO

X(1), Xserver(1)

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). 

COPYRIGHT

Copyright 1988, Massachusetts Institute of Technology. 
See X(1) for a full statement of rights and permissions. 

AUTHORS

Bob Scheifler, MIT Laboratory for Computer Science,
Jim Gettys, MIT Project Athena (DEC).

X Version 11  —  1 March 1988