Requirements

• Have working terminal set up.

X-11 is a protocol for rendering graphical user interfaces (GUIs) that can be sent along an SSH tunnel. If you plan on using a GUI on a NeSI cluster you will need to have an X-Server and X-Forwarding set up.

X-Servers

You must have a X-server running on your local machine in order for a GUI to be rendered.

Download links for X-servers can be found below.

MacOS	Xquartz
Linux	Xorg
Windows	Xming

Make sure you have launched the server and it is running in the background, look for this  symbol in your taskbar 

Note

MobaXterm has a build in X server, no setup required. By default the server is started alongside MobaXterm. You can check it's status in the top left hand corner (=on, =off). 

X-Forwarding

Finally your ssh tunnel must be set up to 'forward' along X-11 connections. 

OpenSSH (terminal)

Make sure the -Y or -X flag is included

ssh -Y user@lander.nesi.org.nz

ssh -Y login.nesi.org.nz

MobaXterm

 Under 'session settings' for your connection make sure the X-11 forwarding box is checked.

If the button in the top right corner of your window is coloured, the X-server should be running.

X-Forwarding with tmux

In order to connect X11 into a tmux session you make the following change to your config file.

tmux show -g | sed 's/DISPLAY //' > ~/.tmux.conf

Interactive Slurm jobs

In order to make use of X11 in an interactive Slurm job:

srun

Add the flag --x11

srun --ntasks 36 --mem-per-cpu 1500 --time 01:00:00 --x11 --pty bash

salloc

add the flag -Y when sshing to the node.

ssh -Y wbn001

XVFB

If your application requires X11 in order to run, but does not need to be interactive you can use X11 Virtual Frame Buffer. This may be required to in order to run visual applications on the compute nodes. Prepending any command with xfvb-run will provide a dummy X11 server for the application to render to.
e.g.

xvfb-run xterm