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XHOST(1)	    UNIX Programmer's Manual		 XHOST(1)



[1mNAME
     [0mxhost - server access control program for X

[1mSYNOPSIS
     xhost [0m[[+-]hostname ...]

[1mDESCRIPTION
     [0mThe _x_h_o_s_t 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 con-
     trol and security.  It is only sufficient for a workstation
     (single user) environment, although it does limit the worst
     abuses.  Environments which require more sophisticated meas-
     ures 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 /_e_t_c/_X*._h_o_s_t_s (where * is the display number of
     the server).  The _x_h_o_s_t 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.

[1mOPTIONS
     [0m_X_h_o_s_t 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.

     [1m[+][0m_h_o_s_t_n_a_m_e
	     The given _h_o_s_t_n_a_m_e (the plus sign is optional) is
	     added to the list of machines that are allowed to
	     connect to the X server.

     [1m-[0m_h_o_s_t_n_a_m_e
	     The given _h_o_s_t_n_a_m_e is removed from the list of
	     machines that are allowed to connect to the server.
	     Existing connections are not broken, but new connec-
	     tion 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.

     [1m+	     [0mAccess is granted to everyone, even if they aren't
	     on the list of allowed hosts (i.e. access control is
	     turned off).

     [1m-	     [0mAccess is restricted to only those machines on the



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XHOST(1)	    UNIX Programmer's Manual		 XHOST(1)



	     list of allowed hosts (i.e. access control is turned
	     on).

     _n_o_t_h_i_n_g 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.

[1mFILES
     [0m/etc/X*.hosts

[1mSEE ALSO
     [0mX(1), Xserver(1)

[1mENVIRONMENT
     DISPLAY [0mto get the default host and display to use.

[1mBUGS
     [0mYou can't specify a display on the command line because
     [1m-display [0mis a valid command line argument (indicating that
     you want to remove the machine named ``_d_i_s_p_l_a_y'' from the
     access list).

[1mCOPYRIGHT
     [0mCopyright 1988, Massachusetts Institute of Technology.
     See _X(_1) for a full statement of rights and permissions.

[1mAUTHORS
     [0mBob Scheifler, MIT Laboratory for Computer Science,
     Jim Gettys, MIT Project Athena (DEC).






















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