The Open OnDemand installation for the Biowulf cluster includes "Graphical Sessions". This special application launches a basic Linux desktop session on the cluster. This session is designed to be somewhere between a login node like Biowulf or Helix and interactive access to a compute node, as with sinteractive.

These sessions may be your primary interface to the cluster, allowing for direct access to a session from your web browser, although unlike the Biowulf login node, you are able to run software appropriate to run on the cluster as long as it does not require more resources than dedicated to the graphical session. Currently Graphical Sessions offer four CPUs and 8 GB of memory per job. Graphical sessions or regular terminals (not sinteractive) in those sessions do not count against your user limit of two interactive jobs.

In comparison with our previous NoMachine service, the Graphical Session presents the same full virtual desktop, however it is running on dedicated resources on special compute nodes and not shared between the hundreds of users of the login node. This does not require any special client software or software updates, instead being accessible purely through your modern web browser. Like NoMachine sessions, Graphical Sessions are persistent and remaining when you log off or disconnect, currently running for up to seven days at a time. Sessions may not be extended beyond seven days.

To access Graphical Sessions, you should launch a "Graphical Session" app from the HPC OnDemand dashboard or directly from the submission form.

When you launch a session, this will schedule a job on your behalf with the Biowulf Slurm scheduler. Generally these should launch within a couple minutes. Submitting the job will redirect you to the "My Interactive Sessions" page. Once the job has successfully started running, your job will turn green and show as Running. Click "Launch Graphical Session" to open a new browser tab to access your session.

• You may launch sinteractive jobs through the Terminal app available in the desktop session.
• You may SSH to Helix through the Terminal application. SSH to Helix allows you to run interactive data transfers to and from the Biowulf cluster as well as access Git repositories via SSH.
• You can access graphical applications running in interactive sessions with automatic X forwarding, no setup required.
• Firefox is available in Graphical Sessions to facilitate file transfers most suitable for web browsers, as an alternative to file transfer with the Helix node.
• You can adjust the image quality via the slide-out menu on the left side of the screen or before launching your job. Lower image quality may help improve responsiveness on slow connections.