Interactive Jobs

Some of the applications available on BlueBEAR make use of a Graphical User Interface (GUI). Some of these are available in the BlueBEAR Portal and that is the preferred method of access for those applications that are available. Where an application is not available in the BlueBEAR Portal you can use an interactive job, with X forwarding enabled in your ssh session, to pass the GUI back to your own computer.

Using an Interactive Job

To start an interactive job, use the following commands:

module load slurm-interactive
fisbatch_screen --nodes=1-1 --ntasks=2 --time=1:0:0

You can send the same arguments to fisbatch_screen as you would put in a job script submitted using sbatch. I.e. to specify a QOS or project. The same limits on resources, such as wall time or number of cores requested, apply to interactive jobs. The example above asks for two cores, on one node, for one hour.

You will then see output similar to:

[info] Waiting for JOBID 3345516 to start
.....
[info] Job 3345516 is running
[info] Job is running on bber0501u32b
[info] Connecting to head node (bber0501u32b)

Once the interactive job has started then you will be connected to the node the job is running on and you will be able to run your job commands here. So, to start MATLAB:

module load MATLAB/2018b
matlab

When you disconnect from the job, by exiting the terminal, then the job will automatically be cancelled. If you use an interactive job then it is your responsibility to make sure that you make good use of the resources.

Warning

Please don’t leave the job idle, and remember to disconnect as soon as you’ve finished your work.

The fisbatch_screen command starts a screen session on the compute node whereas there is an equivalent fisbatch_tmux command that uses tmux instead. These two types are provided because if you wish to start an interactive job within an existing screen (or tmux) terminal multiplex session on a login node then you should avoid nesting screen or tmux sessions by using the alternative fisbatch_tmux or fisbatch_screen respectively. This avoids the issue of the escape-sequences conflicting.

Be aware that there are several login nodes: if you run either screen or tmux as a terminal multiplexer then you will need to ensure that you connect to the same login node when you want to re-attach to an existing session, e.g. ssh _user_@bb-pg-login01.bham.ac.uk instead of the normal ssh _user_@bluebear.bham.ac.uk.

If you have connected to the login node with X forwarding then the graphical X connection will automatically be forwarded from the interactive job. See here for details how to do that on a Windows machine. Linux or Mac uses should use the -X ssh flag when logging in.