Singularity is a container solution created for scientific and application workloads. The objective of this guide is to demonstrate how to use Singularity on the CHPC Lengau cluster.

The diagram below is a visual depiction of the Singularity work-flow process. This process can be categorised into two environments:

• Build environment: for testing and building containers (user needs sudo privileges). This would ideally be the user's workstation or VM.
• Production environment where users run containers. E.g (Lengau Cluster)

For more details please read the user manual: https://www.sylabs.io/guides/2.6/user-guide/index.html

Based on the image above, it is clear that the CHPC Lengau cluster will only provide a production (container execution) environment for the Singularity workflow. Therefore, users are only allowed to run already built containers images on this platform.

NB: Please note that the computes nodes on Lengau do not have access to the internet, which means that users will not be able to use the Singularity pull command. However, users can use the scp.chpc.ac.ca node to facilitate the transfer of images to and from the platform.

Using Singularity on Lengau can be summarised as a two-stage process:

1. Transferring images to the Lengau cluster: Users can use cp, SCP, rsync or FTP to copy their images on the cluster using the node: scp.chpc.ac.za. Alternatively, login to the scp.chpc.ac.za node, load the module chpc/singularity and the use the Singularity pull command to get the images from the respective repository.