Troubleshooting the LUCI1 NX Server

The LUCI1 software runs on a SUN V880 Server, accessed via an NX Client. The machine name is lucifer.mountain.lbto.org or sun.luci.lbto.org and the user id is engineer.

Note that just stopping/starting the server is not enough to restart things. There is no daemon started when you issue the nxserver command:

    /usr/NX/bin/nxserver --start

From Stephen:
If you look at the script, you will see that it is basically just dropping a flag file that either permits or denies entry into the system.

The NX server at this revision is fairly sneaky: they give themselves a shared identity file, and then use the public key to establish a password-less ssh session to an anonymous account over which they then execute the nxserver binary which tunnels its information back through the ssh session where the client then splits it out and runs the display on it.

One of the first things the nxserver does is check to see if the "flag" is there, and if it is then it starts, otherwise it just doesn't run and the ssh session dies.

So, to actually restart NX sessions, you need to:
  1. kill the nxservers you are interested in, and
  2. clean up the cache and logs from /home/${user}/.nx where it keeps the session state

The more modern nxserver actually uses the ssh user authentication rather than a shared key and anonymous account to accomplish much the same thing, but otherwise it is much the same thing.

The session state that needs to be saved is in the user's home directory. This is very inconvenient with multiple users using the computer, but it does explain why "home" space is important to the proper function of the nxserver.
Topic revision: r1 - 02 Jun 2014, KelleeSummers
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