XRSH(1) X Version 11 XRSH(1)
Release 6
NAME
xrsh - start an X program on a remote machine
SYNOPSIS
xrsh [ -help ] [ -version ] [ -l username ] [ -auth authtype ] [
-screen screen-# ] [ -pass envlist ] [ -debug ] [ -debug2 ] remote-host
[ X-command [ arguments ... ] ]
DESCRIPTION
Xrsh runs the given X command on a remote host. It sets up the
environment for that command such that it will display its windows on
the current server's screen by propagating the $DISPLAY environment
variable. If not specified, the default client is xterm. Xrsh
automatically selects rsh(1), remsh(1) or rcmd(1) to execute remote
commands, depending on what is available the O/S environment.
Xrsh automatically handles authentication so that the remote client
will be allowed to open windows on the server. It does this in
several different ways depending on the value of the $XRSH_AUTH_TYPE
environment variable or the -auth argument.
By default, xrsh will use xhost to enable the remote client to open a
server connection. It can also be told to use xauth to merge local
keys into a remote authorization file. Or it can pass the
$XAUTHORITY environment variable to the remote host in order to share
a common NFS mounted authority file. It can also be directed to do
nothing in the case where no explicit authorization is necessary.
Users who just want a remote terminal window might look at xrsh's
sister command, xrlogin(1). Xrlogin uses a locally running xterm to
open an rlogin connection to a remote host. The decision on whether
to use "xrsh host xterm" or "xrlogin host" should be based on several
factors. If X is unavailable on the remote host or the local terminal
emulator has better features, use xrlogin. In general, the author
recommends using xrsh over xrlogin in most situations.
If the command to execute on the remote host is an xterm, xrsh
automatically passes the -name argument to xterm with a value of
"xterm-hostname" where hostname is the name of the remote host. This
allows the user to specify resources in their server's resource
manager which are specific to xterms from a given host. For example,
this feature can be used to make all xterm windows from a given remote
host be the same color or use a specific font or start up in a
specific place on the screen. Xrlogin passes the same string so they
are compatible in this regard. This feature can be overridden by
specifying your own -name argument on the xterm command line.
If the command to execute on the remote host is an xterm, xrsh
specifies that the default title for the new xterm will be
"xterm@hostname" where hostname is the name of the remote host. This
can also be overridden by specifying your own -title argument on the
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xterm command line.
Xrsh is very careful not to leave any extra processes on either the
local or remote machine waiting around for the client to exit. In
some remote environments (particularly some Sys V implementations of
csh and rsh), this is impossible and xrsh should be run as a
background command.
OPTIONS
Note that xrsh options precede the given X command and its arguments.
-auth authtype
Choose what type of X authorization (or access control) is going
to be used. Authtype can be one of "xhost", "xauth", "xhost-
xterminal", "environment", or "none". The default is xhost, but
the default can be set by setting the value of the environment
variable $XRSH_AUTH_TYPE.
If xhost is specified and the X server is running on the local
machine, xhost will be run locally to enable the remote host to
open an X connection. If the server is on a third host (not the
one where xrsh is running and not the one where you wish to run
the command), rsh will be used to run xhost on the server host to
authorize the host where the command will be run.
If xauth is specified, then xrsh will merge the entries for the
server from the local $XAUTHORITY file into that of the remote
host using rsh.
The authtype xhost-xterminal is intended for use by people using
X terminals. If xhost-xterminal is used, then the first time
xrsh is run, it runs xhost locally to enable the remote host for
access. This should work since (theoretically) the first time it
is run is on the XDMCP host for the X terminal. From then on it
propagates the name of that host to all remote hosts via the
environment variable $XHOST. In subsequent invocations from
remote hosts, xrsh uses rsh to connect to the host $XHOST and run
xhost to enable new remote hosts.
Authtype "none" does no explicit work for access control. Use
this if you don't enable access control or if you use another
mechanism for access control.
Finally, authtype "environment" automatically propagates the
environment variable $XAUTHORITY to remote hosts, assuming that
it is an NFS mounted location that can be accessed from all
hosts.
-debug
Normally xrsh redirects standard input and standard output to
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/dev/null in an effort to cause unneeded rshd and shell processes
to exit. As a result, the user can't usually see any errors that
might occur (like a "Permission denied." from rsh). If you are
having trouble getting xrsh to work with a remote host, try
giving the -debug switch to see if any errors are being
generated.
-debug2
This switch causes xrsh to turn on the -x option in the shell so
that the user can see every shell command executed by xrsh. Only
use this script if you are debugging the xrsh code itself.
-help
Print out the argument list to standard output.
-l username
Use the -l switch to specify a different user name to use for
logging in via rsh on the remote host.
-pass envlist
Envlist is a quote delimited string naming an arbitrary set of
environment variables to pass on to the shell environment on the
remote host. If one wanted to set $XRSH_AUTH_TYPE and
$XAUTHORITY to the remote host, one could use: -pass
"XRSH_AUTH_TYPE XAUTHORITY". A default set of environment
variables to pass may be set using the environment variable
$XRSH_ENVS_TO_PASS.
-screen screen-#
Specify a different screen on the server on which to display the
remote client.
-version
Print out version information and exit.
ENVIRONMENT
The environment variables XRSH_AUTH_TYPE and XRSH_ENVS_TO_PASS which
can be used to set switch defaults are overridden if the equivalent
switch is specified as well.
XAUTHORITY
The $XAUTHORITY environment variable is passed to the remote host
if the authtype specified by -auth or $XRSH_AUTH_TYPE is
"environment".
XRSH_AUTH_TYPE
This environment variable can be used to specify the default type
of authorization or access control. The values it can be set to
are the same as the values for the argument -auth.
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XRSH_RSH_ERRORS
If the environment variable XRSH_RSH_ERRORS is set to the name of
a file, any rsh errors will appear in that file on the remote
host. If that variable is unset, error messages will be thrown
away unless the -debug switch is given. (Note: don't use ~ in the
filename because it will expand to ~ on the local host, but try
to put the errors in that file on the remote host.)
XRSH_ENVS_TO_PASS
COMMON PROBLEMS
Make sure your PATH environment variable on the remote host is set in
your .cshrc or .bashrc so that rsh programs have access to it.
(/bin/sh and /bin/ksh users have a hard time time here since their
shells don't execute any init files under rsh. You can use the
XRSH_ENVS_TO_PASS environment variable to pass the PATH environment
variable to the remote host. Optionally, you can type a full path to
xrsh in that case. (E.g. xrsh remote-host /usr/bin/X11/xterm))
Make sure your PATH environment variable on the remote host includes
the directory containing the X programs. This is often /usr/bin/X11
or /usr/local/bin/X11.
Make sure you have rsh configured to work on the remote host. You can
test this by typing: rsh remote-host echo '$PATH' This will prove
that rsh works and show you the PATH that will be used on the remote
host. If you get "Permission denied." you probably need to update
your ~/.rhosts file on the remote host. See rlogin(1).
EXAMPLES
xrsh yoda
Start an xterm on the host yoda which displays on the current X
server. Use xhost for access control.
xrsh -auth xauth underdog emacs
Start an emacs on the host underdog. Merge xauth authorization
entries for this server into the authority file on the remote
host.
xrsh -l mjd -auth none -pass XRSH_AUTH_TYPE -debug tigger xterm -
fn 5x7
Start an xterm on the host tigger in a very small font, propagate
the environment variable $XRSH_AUTH_TYPE to the remote host,
login to the remote host using the id "mjd", don't do any
specific authorization and don't redirect standard/error output
to /dev/null so I can see any errors.
BUGS
If the values of the environment variables specified in -pass or
$XRSH_ENVS_TO_PASS contain quote characters, xrsh will have
difficulty.
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If the remote host can't resolve the hostname of the server host
(through /etc/hosts, DNS or NIS), the remote client will not be able
to open a connection to the server.
System V users may need to make the first line of the script begin
with colon (:).
If you think you have found a bug, the first thing you should do is to
check on ftp.x.org in the contrib directory using anonymous FTP to see
if there is a new version of xrsh there that already fixes the bug.
If not, send email to "jjd@bbn.com" and be sure to have the token xrsh
somewhere in the Subject: line. Be sure to report the operating
system type and version at both ends of the xrsh connection and a
description of the command you are using and what authentication mode
you are using.
SEE ALSO
xrlogin(1), rsh(1), xhost(1), xauth(1)
AUTHOR
James J. Dempsey <jjd@bbn.com> with help and suggestions from many
people including gildea@expo.lcs.mit.edu, dm@think.com,
dgreen@cs.ucla.edu and rosen@cns.bu.edu,
<eero@whitechapel.media.mit.edu>, and
<martin@whitechapel.media.mit.edu>.
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