Exercises 1: Elementary access and the HPE Cray PE

• Start with the exercises on "Getting Access to LUMI"

• Continue with the exercises on the "HPE Cray Programming environment"

Q&A

1. I am not sure how to properly switch from one node to the other when I logged in through OnDemand. Do I understand it correctly, that I need to create a private key in my home directory (on LUMI) to do that?

   • I'm not sure i understand what is your goal. if you want to go to compute nodes you need to use srun for it (see https://docs.lumi-supercomputer.eu/runjobs/scheduled-jobs/interactive/ section use srun to check running jobs). Otherwise if you want to go to another login node indeed you have to have an ssh key and use agent forward. It is not possible to ssh in a compute node. This is due to LUMI having shared nodes and cgroup is limiting visibility if you have a partial allocation only via slurm, and allowing ssh to compute node would circumvent this.

   • You cannot create keys in .ssh on LUMI. They will be ignored for security reasons. You also cannot ssh to a different node on LUMI. I think for the login nodes you would go through the external network interface anyway, and as we will see tomorrow, you cannot ssh to a compute node. The only way to add a key is through myCSC for CSC accounts and MyAccessID for all other accounts, see the "Setting up SSH key pair" page in the LUMI documentation.