To simplify the remote access of Thor, and other systems, from
Linux boxes the Computing Service provides a superior version of the
standard X xon program called xcmd. If your
system administrator has not already installed this program on your
local box, you should download it and install it somewhere where you
can run it.
NB: The xcmd program only works on Linux boxes or
other systems that support the -f option on
hostname.
xon and xcmd work by using
rsh to execute a command on the remote system. The
xcmd script automatically arranges that the target
command is run with the correct DISPLAY set. The default command is
an xterm.
However, for Thor to accept the rsh request at all,
you will need to have a .rhosts file set up on Thor
trusting your account on your Linux box. If your account name on Thor
is different from your local account name then you will need to use
the -user option on xcmd to pass through
your Thor account name.
local$ xcmd hammer.thor xbiffxbiff on the machine
hammer.thor.cam.ac.uk. The account name on Thor must
match the local account name. local$ xcmd gloves.thor -user rjd4 emacsemacs on the machine
gloves.thor.cam.ac.uk. The account name on Thor is
rjd4 regardless of the local account name. local$ xcmd belt.thorxterm on the machine
belt.thor.cam.ac.uk. The account name on Thor must match
the local account name. Once the command has been started on Thor, the X client
(xbiff, emacs or xterm in the
examples above) still has to make an X connection back to the server.
This has a different set of permissions, dealt with by the
xcmd's -permit option. (This is the
principle extension that xcmd has over xon.)
The first time you use xcmd during a given X session
you should run it with the -permit option to transfer the
relevant authority to Thor. You can either run it with a true X
client, the default xterm or with a "null"
command such as true to do no X work at all, but just
transfer the authority:
local$ xcmd hammer.thor.cam.ac.uk -permit xbiff permitted hammer.thor.cam.ac.uk access to gryphon.csi.cam.ac.uk:0.0 local$ xcmd hammer.thor.cam.ac.uk -permit permitted hammer.thor.cam.ac.uk access to gryphon.csi.cam.ac.uk:0.0 local$ xcmd hammer.thor.cam.ac.uk -permit true permitted hammer.thor.cam.ac.uk access to gryphon.csi.cam.ac.uk:0.0
The xcmd command has a -help option
which lists all its options.