Frequently Asked Questions

Using the cluster is free of charge.

Neither for your user account nor for your project usage, you or your academic institution will be charged in any way.

However, operating and maintaining the HPC is quite an expensive business nonetheless (power consumption, cooling, administration). The compute resources should thus be used responsibly, by designing your compute jobs as efficient as possible.

There are regular office hours, but no support chat.

Video office hours every Wednesday 10 am 11 am:
Zoomlink
Meeting-ID: 665 7163 2291
Kenncode: 113329

Office hours every first Wednesday (monthly):
Alexanderstrasse 2, Room 205, 213 und 214

While logged in on one of the login nodes , you can use the command account_expire to see your user account's end-of-validity date.

You will get an automatic email reminder 4 weeks before expiry of your account, and another one on the day of expiry.

These go to your professional TU-ID mail address configured in the TUDa's IDM system.

To extend your account, simply fill and sign the "Nutzungsantrag " again, and send it to us fully signed via office post (or via your local contact person ).

That can be caused by two basic reasons: the login node is not answering at all (perhaps due to being down or having network problems), or it answers but denies you access.

• Try another login node (the one you tried may be down)
• Have a look at our news page for possible maintenance downtimes or unexpected outages.
• Check your professional email inbox (and spam folder) for mails with the subject “Your account on the Lichtenberg High Performance Computer”, warning of or indicating your recent account's expiry.
• In case of “Permission denied” or “Incorrect password” (the login node answers, but denies you access), even from different login nodes:
  • check the language settings of your keyboard for inadvertent changes. English keyboard layout has Y and Z inverted, and does not sport german umlaut's.
  • make sure to log in with your TU-ID. Some ssh programs guess your login name from what you are on the local system, ie. the windows ssh client likes to transmit “ADS-DOMAIN\yourWindowsName” and that can't work. Either use
    ssh <TU-ID>@lclusterXX.hrz.tu-darmstadt.de or
    ssh -l <TU-ID> lclusterXX.hrz.tu-darmstadt.de
  • try changing your TUID password, as this is sync'ed to the HLR a few seconds later.
• Read the (ssh) error message in its entirety. Sometimes it even explains how to fix the actual problem.
• Try to log in explicitly with IPv4 or IPv6:
  ssh -XC –4 <TU-ID@>lcluster15.hrz.tu-darmstadt.de
ssh -XC –6 <TU-ID@>lcluster17.hrz.tu-darmstadt.de
• Already running the most recent version of your ssh/scp access program (PuTTY / KiTTY / BitVise / WinSCP / FileZilla)?
  From time to time, we refine the allowed (ie. considered safe) list of ssh key ciphers and negotiation algorithms, and some older program (versions) might be unable to cope with them.
• Have you recently made any changes in your login startup scripts .bashrc or .bash_profile? When failing, commands in these startup scripts can cause the bash to end prematurely, and that might look like you are denied access.
  If only interactive logins are affected, you can try accessing the likely culprit with your scp program (BitVise / WinSCP / FileZilla), and either
  • download it, comment the recent changes and re-upload it
    or
  • delete the troublemaker (and then restoring your last version from .snapshots/)

If nothing of the above works out: open a ticket, always mentioning your TUID (no enrollment/matricle no) and preferably from your professional TUDa email address.

Avoid sending “screenshots” of your terminal window as pictures (jpg/png or the like). A simple copy&paste in text form of your login attempts and the resulting error message is sufficient.

If there isn't any explanatory error message, please use the “verbose” mode by running “ssh -vv …” and append the output to the ticket mail (again please not as screenshot/picture, but as text).

Since June 2020, we have established a new password synchronisation: as soon as you change your TUID password in the IDM system of the TU Darmstadt, the login password to the Lichtenberg HPC will be in sync with it.

For new users, this is in effect from the get-go, ie. their first login to the Lichtenberg HPC will work with their central TUID password.

Existing users will keep their current password (the one last set on the “HLR” tab of the former “ANDO” portal).
As soon as they change their TUID password on the IDM portal, it will overwrite the last HLR password.

The same holds true for guest TUIDs.

Using the "member “ command (new since Nov 2022) without parameters, you see a list of all your memberships in HPC projects.

Additionally, your currently active projects / memberships are recorded nightly in a file called .project in your HOME directory:

 cat $HOME/.project

(see also ”Hints " about project application).

• Director of the institute (DI): Most departments are organized into institutes (Fachgebiete). If this does not apply to your organization, please insert the dean, or a person with staff responsibility for the main research group.
• Principal Investigator (PI): is responsible for the scientific aspects of the project. This can be the DI, as well as a junior professor or postdoc.
• Project Manager / Person of Contact (PoC): In general, this is the main researcher working the major part of this project. The PoC is responsible for the administrative aspects of the scientific project. He or she is also the “technical contact” the HRZ communicates with.
• Member or Additional researchers (AR):All other researchers who can do computations on this project's account. These might be other colleagues, PhD students, team members, as well as students and student workers.

The general project classes by amount of resources (Small, NHR-Normal and NHR-Large) are listed in our project class overview .

Beside plain computational projects, you might also be member of some rather technical billing accounts (eg. courses/trainings).

In general, we have the following naming pattern:

• project<5#>
  This is a Small (or preparation) project
• p<7#>
  This is a NHR project (Normal or Large)
• special<5#>
  Technical projects for select groups
• kurs<5#>
  Trainings, workshops and lectures with practical exercises on the Lichtenberg cluster (see Lectures and Workshops ).

In general, one main researcher (PhD or post-doc) owns a project, ie. is project manager. This main researcher or PM can decide to add others to his or her project, for instance bachelor or master students, or a colleague he or she is collaborating with on this project.

All these coworkers need to have their own user account on the HLR before being added to a project.

Beware: while sharing your project account is explicitly allowed, sharing your user account is strictly prohibited!

In general, the Lichtenberg “local” or Small projects should be in the range and size of a PhD project, or intended to prepare NHR-Normal or -Large projects. For longer research terms and scientific endeavours, recurring follow-up projects are required.

Nonetheless, the initial proposal should outline the whole scientific goal, not only your 1^st year's targets.

If the limit of a Small project is insufficient for your scientific challenge, apply for a NHR-Normal or NHR-Large project.

The project manager (PM or PoC – Person of Contact) is responsible for applying and (after completion) for reporting on the project.
He will be working with the HRZ for the (technical) reviews, and hand in the original of the signed proposal to the HRZ.

Students can apply for a bachelor or master thesis' project.

The proposal has to be signed by the PM and by the PI, who is required to be professor or post-doc.

For a “Small” (or preparation) project, only the web form needs to be completed, printed out, signed and sent to the HRZ.
This form mainly asks for technical details and a short abstract (150-300 words) of the scientific goals.

For the larger NHR projects, refer to the JARDS portal for details.

“Small”/preparation projects can be submitted at any time and the proposals will be handled upon entry.

For the larger NHR projects, deadlines (if any) can be found on the JARDS portal.

All projects are subjected to a technical review by the HRZ/HPC team.

If a project proposal is not sufficiently clear (ie. in terms of job sizes and runtimes), we wil contact the PM and ask for clarification or modification.

After the TR has been completed successfully, “Small” projects are started immediately.

NHR-Normal and NHR-Large projects are then scrutinized scientifically by (external) HPC experts from the field of the project.

Based on these reviews, the steering committee (Resource Allocation Board) approves (or denies) the proposal and assigns the resources, either as requested or in reduced form.

The minimum is 3 months, and the maximum grant period for any given project is one year, regardless of the project's class.

If you know that your project needs less than a year, we suggest to write your proposal accordingly.
As the computational resources are allotted evenly over the granted time period, shorter projects get a greater resource share per month, resulting in higher priority per job.

In well-reasoned cases, a project can be extended beyond one year, for one or two months.

If your research project will take much longer than a year to complete, you will need to apply for follow-up projects every year.

Like you do it with your coworkers, referencing substantial contributions to your research publications should include the computational time grants from the Lichtenberg cluster. Properly communicating them improves public understanding of how research funds for HPC are spent and how we are working to support your research.

We thus kindly ask for an acknowledgment in all your publications arose out of or having used calculations on the Lichtenberg:

The authors gratefully acknowledge the computing time provided to them on the high-performance computer Lichtenberg at the NHR Centers NHR4CES at TU Darmstadt. This is funded by the Federal Ministry of Education and Research, and the state governments participating on the basis of the resolutions of the GWK for national high performance computing at universities (www.nhr-verein.de/unsere-partner).

If having been supported by the HKHLR, you could add:

The authors would like to thank the Hessian Competence Center for High Performance Computing – funded by the Hessian State Ministry for Higher Education, Research und the Arts – for helpful advice.

For all TU Biblio publications, the category „Hochleistungsrechner“ within the „Divisions” list (as a subcategory of „Hochschulrechenzentrum“) was added to TU Biblio.

Please use this category for your research publications related to the Lichtenberg Cluster, as then your publication will automatically be listed here accordingly.