FAQ

If your job is the only job on the node (e.g. you specified the --exclusive flag) you may simply use ssh <nodename>. SSH connections to compute nodes are only permitted if a user has a running job on it.

If your job shares the node with other jobs you should use srun --pty --overlap --jobid=<jobid> /bin/bash, which will connect your terminal to the already running job. You will have access to the exact same resources, that your job allocated. Thus, it is not possible to confuse your resources with the ones from other jobs.

The following commands expect an SSH config entry as it is shown here as well as a recently successfully performed two factor authentication to the same login node, from the same IP, and with the same key, within the last 14h.

Data can be copied to and from the cluster using scp, or rsync. We strongly recommend rsync due to the many quality of life features.

# Copy local to cluster
rsync -r --progress --compress --bwlimit=10240 <local_source_path> login001.elysium.hpc.rub.de:<remote_destination_path>

# Copy cluster to local
rsync -r --progress --compress --bwlimit=10240 login001.elysium.hpc.rub.de:<remote_source_path> <local_destination_path>

The paths to the data which shall be copied and the destination, as well as the username need to be adjusted. Note that there is no trailing “/” at the end of the source path. If there was one, the directories contents, not the directory itself would be copied.

Flags:

• -r enables recursive copies (directories and their content)
• --progress gives you a live update about the amount that has been copied already and an estimate of the remaining time
• --compress attempts to compress the data on the fly to speed up the data transfer even more
• --bwlimit limits the data transfer rate in order to leave some bandwidth to other people who want to copy data, or work interactively.

If multiple file are to be copied to/from the cluster, the data should be packed into a tar-archive before sending:

# create a tar archive
tar -cvf myfiles.tar dir_or_files.*

# extract a tar archive
tar -xvf myfiles.tar

Note that running multiple instances of rsync, or scp will not speed up the copy process, but slow it down even more!

Compute nodes can only connect to hosts in the university network by default, and for good reasons. Only the login nodes have internet access.

Please organize your computations in such a way that internet access is only required for preparation and postprocessing, i.e. before your computations start or after they end. For these purposes, internet access from the login nodes is sufficient.

If you absolutely must access hosts outside of the university network from a compute node, you can use the RUB WWW Proxy Cache: export https_proxy=https://www-cache.rub.de:443. However, make sure to use the cache responsibly, and keep in mind the following drawbacks:

• Your computations depend on the availability of external network resources, which introduces the risk of job failure and therefore waste of resources.
• The proxy cache may be bandwidth limited.
• Network transfer times on compute nodes are fully billed in the FairShare system.

According to the Terms of Use, publications must contain an acknowledgement if HPC resources were used. For example:

“Calculations (or parts of them) for this publication were performed on the HPC cluster Elysium of the Ruhr University Bochum, subsidised by the DFG (INST 213/1055-1).”

We maintain a list of such publications, updated in regular intervals.

Running calculations on the login nodes is prohibited. This is to keep the resources free so that everyone can do their work e.g. login, edit inputs, read outputs, compile codes. If you need to do interactive calculations, to test your setup or analyse data, you should reserve an interactive node. You can get an interactive session on the vis nodes with the following command:

srun -N1 --partition=vis --exclusive --time=08:00:00 --tasks-per-node=1 --account=<account_name> --pty /bin/bash

If you require a specific node to run your interactive session on you can specify it with the -w <nodename> flag.

On the Elysium cluster the job queue is sorted by priority. The priority of a job depends on the recent resource usage of the user, the project, the group, and the organizational unit. If one of these utilized more resources than they are entitled to, priority of all its members drops. If one of these utilized fewer resources than they are entitled to, priority of all its members rises. You can see your priority with the sshare command:

$ sshare
Account                    User  ...   FairShare 
-------------------- ----------  ...  ---------- 
project1              myloginid  ...    0.008715 
project2              myloginid  ...    0.279608 
project3              myloginid  ...    0.930501 

The rightmost column shows the priority on a scale from 0 (lowest) to 1 (highest).

To get estimated start times for your job you can use the scontrol show job <jobid>:

$ scontrol show job 123456
JobId=123456 JobName=MyJobName
   UserId=myloginid(33333) GroupId=hpcuser(100000) MCS_label=N/A
   Priority=1061002392 Nice=0 Account=project1 QOS=normal WCKey=*
   JobState=PENDING Reason=Priority Dependency=(null)
   ...
   SubmitTime=2026-01-21T21:37:45 EligibleTime=2026-01-21T21:37:45
   AccrueTime=2026-02-21T21:37:45
   StartTime=2026-01-25T02:40:56 EndTime=2026-01-25T03:10:56 Deadline=N/A
   ...

Note that the listed StartTime is only an estimate. If currently running jobs terminate before reaching their walltime, your jobs might start earlier. If more prioritized users submit more jobs, your jobs might start later.

If you supplied job parameters that can never be fulfilled by any partition that was specified in the submission script, or submission command, the scontrol show job will show StartTime=Unknown. In that case you may contact us via hpc-helpdesk@ruhr-uni-bochum.de to get help.

The storage resource limit was exceeded. The available storage systems and their limits (quotas) are listed here. Use the rub-quota command to check your current storage usage e.g.:

$ rub-quota 
You used 1.68G of your 100G Quota in 68.0K files, file limit is set to: none files for /home 
You used 2.8T of your 4.395T Quota in 1337 files, file limit is set to: 1900000 files for /lustre