Accessing the System

Accessing the System

Logging on from a Desktop

You can use your linux user ID (as given to you by Mark Slater) and password to log on to any of the desktops in the department. As the home areas are mounted from a single server you should have the same environment and settings no matter which desktop you use.

Connecting via SSH

To log in to the PP system remotely via SSH depends on your OS: Windows users should use Putty, for MAC and Linux, ssh is provided so just open a terminal and type 'ssh ...'

As regards which machine to access and where from, for basic terminal access similar to Lxplus, use or These are dedicated 'login' nodes that can always be connected to from CERN, phymat or on campus so login to those first and then use 'ssh user@eprexa...' to log into the cluster. From the login nodes, it's also possible to then log in to the individual desktops.

Direct connections to the login nodes can be made if you have a grid certificate, load it in your browser and go here. If you get an 'Invalid Certificate' error, see the help on this page.

If you are a member of staff or PhD student, you can apply for remote access using a VPN client. Go to the Service Desk and request 'Remote Access'. This should allow you to download the VPN client. For more info, see this knowledge base article. After connecting through the VPN, you can log in directly to eprexa/b and also the office desktops.

Finally, if all else fails, you can email MWS with your IP address as found by going here. I'll add it ASAP to give you access to the login nodes.

File Access

Again, this depends on the OS. WinSCP is a great graphical solution for Windows. For MAC and Linux, 'sshfs' is a good and freely available solution that allows access to your remote directories over SSH. For Linux, use your normal package manager. For Mac download the pkg from here and the required Fuse package here. After doing this, you can 'mount' you home area (or any other folder you have access to on our system) remotely using:

sshfs user@...:/remote/dir/to/access /local/dir/to/put/it

You can then browse it just like a normal directory. Be aware that you need to keep a constant internet connection for this to work!

Graphical Access

Due to the slowness of X sessions and the fact that I've seen many problems recently with MAC and XQuartz, I would recommend using VNC if you need graphical access to one of our machines. To do this, first install Tiger VNC from, or more directly, from it's bintray page here on your local machine.

Next, choose the machine you want to run VNC on (and I would strongly recommend your own desktop in the department if possible!). When logging in, you will need to 'tunnel' the connection through as the firewall is blocking the normal VNC ports. This is a lot easier than it sounds - for each machine you log in to before the final machine running VNC (e.g. Lxplus and then eprexa), log in using the following:

ssh -4 -L 59nn:localhost:59nn user@machine...

where nn will be the desktop number used below. Nore that for Putty, it's a little more complicated. There's a decent description here - just change the source port to 59nn and the destination port to localhost:59nn.

For the 'final' connection to eprex or epldt, do the same:

ssh -4 -L 59nn:localhost:59nn user@epldt...

and then from the terminal window you get to, run the following to start a VNC desktop running:

vncserver :nn -localhost

again, where nn is a number between 0-99, dropping the leading zero if there is one (pick any number you like - it'll tell you if another VNC server is running on this port!). It's best to stick with the same port number through all tunneled machines but technically, you can tunnel the 59nn from eprex/epldt to any port number > 1024.

You should now be able to start Tiger VNC and connect to localhost:59nn and it should ask you for a password that you will have set up when first running vncserver. This should hopefully present you with a desktop just like one of our machines! You can close this window and log out whenever you want. As long as you follow the above instructions to log back in then your desktop will be kept running just as you left it. The only other thing to note is that the speed with which the desktop starts up seems to be very dependant on the number of other VNC sessions running so it can take up to >10mins on eprexa/b - another reason to use your desktop if you can!

If you have finished using a VNC server, then you can kill it and any associated processes by doing:

vncserver -kill :nn

again, dropping the leading zero if necessary.

Finally, if you start the VNC viewer and see a desktop but can't click on anything, even after waiting a few minutes (it can take some time to start up) then try removing the file:


and, if you have it, the folders:

~/.cinnamon ~/.gnome ~/.gnome2