One of the main features of the SCC-Pilot is that we offer so-called "Interactive Jobs". This means that you can get a full desktop environment on one of the compute nodes. Alternatively, you can also connect Visual Studio Code to it. If you only need shell access, it gets even simpler.

Why?

Because you can get computing resources you probably do not have on your laptop or workstation. Like 64GB of RAM or very powerful CPUs. And you have direct access to your home folder.

How?

Desktop or Visual Studio Code Tunnel

Head to the web portal: https://ood.scc-pilot.plus.ac.at and log in with your username and password.

Then, click on "Interactive Apps". If you want a desktop in your browser, choose "xfce-desktop".

For a connection to Visual Studio Code, you first need to do some setup on your computer. Please follow the instruction here. Then, choose "tunnel" from the list of interactive apps.

Note that field at the bottom that says "Apptainer Image"? You can leave this blank and run your interactive job directly on the software stack provided by the SCC-Pilot. Alternatively, you can point it at an Apptainer Image (either the full path on the SCC-Pilot or a URL that Apptainer supports). If the image fulfills all the requirements (see below), your interactive job is going to start there.

If you want to try this out, you can use this link: oras://ghcr.io/thht/obob-singularity-container/xfce_desktop:latest

Once it is submitted, wait a bit for it to run and follow the instructions on the screen.

Shell Access

If you only need shell access, you can login to one of the login nodes and use srun to start an interactive job. Here is an example:

srun --qos=interactive --cpus-per-task=2 --mem=2G --time=120 --pty bash

You can also use apptainer to start the job in a container and use a different shell:

srun --qos=interactive --cpus-per-task=2 --mem=2G --time=120 --pty apptainer shell -s /bin/zsh oras://ghcr.io/thht/obob-singularity-container/xfce_desktop_minimal:latest

What is this QoS?

QoS means "Quality of Service" and in this case, you see the "interactive" QoS.

A job submitted to that QoS runs almost instantly because it gets a much higher priority than other jobs and it is also allowed to preempt (i.e. cancel) other jobs. This way, you don't need to wait for other jobs to finish before using your interactive job.

However, note that you can only have one job at a time in the interactive QoS!

Apptainer Images Requirements

If you want to use an Apptainer Image, it needs to fulfill the following requirements:

xfce-desktop

• Have a full installation of xfce installed
• TurboVNC must be installed and in the PATH.
• websockify must be installed and accessible via the /opt/websockify/run.

You can take a look at a working apptainer def here.

Tunnel

• OpenSSH Server must be installed

Shell Access

• Nothing