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Interactive Job Sessions

For an interactive session, you reserve some compute nodes via the scheduler and then are logged in live, just like on the login nodes. These can be used for software debugging, or to work up a script to run your program without having to submit each attempt separately to the queue and wait for it to complete. It is not possible to have an interactive job session with a GUI interface as there is not an X-Forwarding system installed in DSH Desktop.

Requesting Access

You will be granted an interactive shell after running a command that checks with the scheduler whether the resources you wish to use in your tests/analysis are available. Interactive sessions are requested using the qrsh command. It typically takes the form:

qrsh -pe mpi 8 -l mem=512M,h_rt=2:00:00 -now no

In this example you are asking to run eight parallel processes within an MPI environment, 512MB RAM per process, for a period of two hours.

All job types we support on the system are supported via an interactive session (see our examples section). Likewise, all qsub options are supported like regular job submission with the difference that with qrsh they must be given at the command line, and not with any job script (or via -@).

In addition the -now option is useful when a cluster is busy. By default qrsh and qlogin jobs will run on the next scheduling cycle or give up. The -now no option tells it to keep waiting until it gets scheduled. Pressing Ctrl+C will safely cancel the request if it doesn't seem to be able to get you a session.

More resources can be found here:

Working on the nodes

If you want to run a command on one of your other allocated nodes, you can use a standard ssh command from the interactive session to access other nodes within your allocation: 

ssh <DSH_system_name> <command> [args]

Note that you are not able to ssh directly from the login node

In the above, <hostname> can be obtained by inspecting the file $TMPDIR/machines. (CHECK THISSSS)

GPU test nodes

You can also run GPU jobs interactively simply by adding the -l gpu=1 or -l gpu=2 options to the qrsh command as normal.

For more information, please contact us on our contact page.