When users are off-site or have slow internet connections, displaying graphics can be cumbersome. PCDS has explored two solutions for this problem:
This page is about the usage of NoMachine for providing NX technology to users involved in LCLS experiments or operations.
NoMachine NX is supported on Windows, MAC and Linux computers. You can download the latest version of the client from www.NoMachine.com. Ubuntu/Mint users should download the Debian version of the NoMachine client.
LCLS is currently making three different servers available for remote connections:
The allocation of theses servers to the various activities is just to provide a low-tech load balancing and is not enforced.
After opening a connection to one of these servers using your SLAC UNIX account, make sure to run in console mode: from the 'Custom session' dialog window, accept the default options (Application - Run the console, Options - Run the command in a floating window) by clicking Continue.
For performance and reliability reasons we have disabled the ability to open a remote desktop (GNOME) on the NX servers. We plan to keep allowing only the console mode for the foreseeable future since the multiple GNOME sessions were taking too many resources on the NX servers. Let us know if you see any fundamental reason why the ability to open a remote desktop is required to do your job.
This will open a remote terminal on your local desktop from which you can type the name of the application you want to launch. For example, you can type "xterm&
" to open additional terminals or "emacs&
" to open the emacs
editor. Type "ssh -Y psana
" to connect to the interactive pool to do data analysis. When you disconnect and reconnect to NoMachine, these terminals and applications will remain in the state you left them in.
Please contact pcds-help@slac.stanford.edu if you need more information or additional assistance with NoMachine.
If you are not able to connect to NoMachine, check the followings:
Sometimes users will find that they are unable to reconnect to an existing session, and are shown only a blank screen. We do not yet understand this issue, so our solution is to terminate the user's existing sessions, and kill all the user's running processes on the NoMachine server. The easiest way for the users to deal with this is to send a note to pcds-it-l@slac.stanford.edu and we will remove all old sessions and process.
It's also possible for users to fix with this themselves by ssh'ing to psnxserv.slac.stanford.edu and killing their own process. Potentially useful commands follow:
ps -f -u $USERNAME
kill <PID>
kill -9 <PID>
pkill -u $USERNAME
Note that the user will have to reconnect after running pkill
and may have to try a number of times (possibly using the -9 option, as shown with the kill
command).
If you are not able to resume a NX Connection and you typically connect from multiple computers, be sure to use similar version of NoMachine client where you initiate the connection from. To check for NoMachine version, after you have launch NoMachine client, go to Preferences on top, then click on Updates, it will show you the version that you are running NoMachine on.
If Ctrl-C (Ctrl-break) does not work on the Linux client, hit the Alt-Ctrl-C (Use it in proper sequence so hold down the key one at a time). WindowsKey-Ctrl-C, or turn on Caps Lock and hit Ctrl-C will also work.