To be able to use programs on the EMU compute servers, you often need access to a graphical user interface. With Unix, the traditional way has been through ssh -X to export your display from the compute server to your laptop.

While this still works, it can be slow, and more problematically if your connection drops then the program terminates.

I think you will find that VNC works better - a more responsive interface, and a session that remains running if your connection drops.

I can arrange that you are presented with a login screen via VNC and you use your programs after logging in, but I find that very limiting. Firstly you have a fixed screen resolution, that may not correspond to your laptop, and the color depth is also not something you can control.

So I think it is best if you use the slightly more complicated procedure below for a better overall experience.

Which brings me to the next issue - screen resolution. You will probably find that the desktop/application is too small. vncserver has a default resolution of 1024x768 - too small for 2020.

Coupled with screen resolution comes screen depth - the colour quality of the VNC client. Better quality brings better colours, but higher bandwidth and latency.

Step 1 - log in to your chosen server via ssh. This requires you to be using the UCT VPN.

Step 2 - I use this :- vncserver -geometry 1920x1080 -depth 8

I use that resolution because it is the native resolution of my laptop, and I use 8 bit colour to give a snappier feel with terrible colours.

You can make your own choices. Colour depth can go up to 32.

It will report something like this :-

Desktop 'TurboVNC: (administrator)' started on display

Starting applications specified in /usr/local/bin/xstartup.turbovnc
Log file is /home/administrator/.vnc/

The important thing to note is the number of the new 'X' desktop - in this case :2.

Returning to your own laptop, you can start up VNC, set the screen size and resolution, and then connect to

You can now connect with your local (Windows, Mac, or Linux) VNC client program. On Linux, I use Remmina - there are others.

Your VNC client will need the hostname, and number. The number is actually 5900 + number - so desktop 2 above is accessed from Remmina as “” - your client may or may not need the 5900 offset.

On linux, using Remmina, I open a new connection profile, give it a name, use the Remmina VNC plugin for the protocol, use the Basic tab, fill in the host and port number as

I fill in the username, but leave the password field as blank (to be filled in at connection time). I select a Custom resolution, with something suitable for my desktop, like 1920x1080. For colour depth, there is a tradeoff between speed and colour - I choose 8bit, for speed. Now you can save this profile, and just click on it next time.

Again - if you have a long-running graphical program running on cerberus, you can disconnect your VNC client, log off, go to sleep, log in tomorrow, and your program will have been running the whole time.