Login nodes

Hábrók has five login nodes that can be used to connect to the system. Besides redundancy reasons (you can always try another one if one of them is down), they all serve different purposes.

This is the default login node that is used by most users. You can use it to connect to the system, copy your files, submit jobs, compile your code, etcetera. You should not use it to test your applications, since this might slow down the system, which will hinder other users who are trying to log in. It is also a smaller system.

The interactive node is similar to a default compute node, and it allows for a bit more testing. If you just want to run your program for a couple of minutes, this is the machine to use. Do keep in mind that this is also a shared machine and other people may also want to do some testing. So, if you need to do more intensive testing, consider submitting them as jobs.

Finally, the interactive GPU node is a login node equipped with two GPUs. You can use it to develop and test your GPU applications.

This machine has an NVIDIA V100 GPU, which has been subdivided into four smaller GPUs. The tool nvidia-smi will show if/which GPUs are in use, and you can select the one you want to use by setting CUDA_VISIBLE_DEVICES to a number ranging from 0 to 3, to select one of the GPUs. E.g.:

export CUDA_VISIBLE_DEVICES=2

Please keep in mind that this is also a shared machine, and more users want to use the GPUs in this machine. So, allow everyone to make use of these GPUs and do not perform long runs here. Long runs should be submitted as jobs to scheduler.