HCC Class Info for Students

The Holland Computing Center (HCC) provides high-performance computing resources for Universities and Colleges in the state of Nebraska. HCC supports both research and creative, and class activity.

This guide provides a list of useful links for classes utilizing HCC resources.

Useful links for students

Account creation and setup

• New user account form, https://hcc.unl.edu/new-user-request/
• If you already have existing HCC account, use the Add/Change group request form instead, https://hcc.unl.edu/group-addchange-request
• How to activate HCC Duo, https://hcc.unl.edu/docs/accounts/setting_up_and_using_duo/
• How to reset your HCC password, https://hcc.unl.edu/docs/accounts/how_to_change_your_password/
• What are good HCC practices, https://hcc.unl.edu/docs/good_hcc_practices/

Application links

• HCC Open OnDemand (OOD) web access to Swan, https://swan-ood.unl.edu/
• Detailed HCC Open OnDemand guide, https://hcc.unl.edu/docs/open_ondemand/
• Creating custom CPU/GPU conda environments, https://hcc.unl.edu/docs/applications/user_software/using_anaconda_package_manager/#creating-custom-anaconda-environments
• Various SLURM examples of applications that run on Swan, https://github.com/unlhcc/job-examples/
• How to share data across group members, https://hcc.unl.edu/docs/handling_data/swan_data_sharing/

Training

• HCC info sheet, https://go.unl.edu/hcc_info_sheet
• HCC SLURM scheduler cheat sheet, https://go.unl.edu/hcc_slurm_cheatsheet
• Conda user cheat sheet, https://know.continuum.io/rs/387-XNW-688/images/conda-cheatsheet.pdf
• YouTube videos of previous HCC training events, https://www.youtube.com/@hollandcomputingcenter8962
• Upcoming HCC events, https://hcc.unl.edu/upcoming-events

Support

• For issues related to classwork or assignments, please contact your TA.
• For general HCC issues, please first check the FAQ page, https://hcc.unl.edu/docs/faq/.
• For issues with HCC resources (e.g., unavailable resources, sudden errors and job failures), contact HCC support at hcc-support@unl.edu. Please note that non-critical tickets/issues will be addressed during business hours (Monday through Friday, 9am-5pm CST). Critical issues include, but not limited to, sudden unavailability to login and file-system irresponsiveness for all HCC users.

Useful notes for students

• The login node is shared among all HCC users and it should be used only for light tasks, and not for running computationally intensive tasks. For any CPU or memory intensive operations, such as testing and running applications, one should use an interactive session (https://hcc.unl.edu/docs/submitting_jobs/creating_an_interactive_job/), or submit a job to the batch queue (https://hcc.unl.edu/docs/submitting_jobs/).
• If the Open OnDemand resources are not enough, you can run JupyterLab Notebooks within SLURM job, https://hcc.unl.edu/docs/applications/submitting_jupyter_code/running_jupyter_lab_code.
• Custom conda environments are created in $HOME by default. You can change the location of the conda environment, https://hcc.unl.edu/docs/applications/user_software/using_anaconda_package_manager/#using-common-for-environments/.
• Custom conda environments can easily fill the 20GBs quota on $HOME. To clean space, you can remove unused Anaconda packages and caches, https://hcc.unl.edu/docs/applications/user_software/using_anaconda_package_manager/#remove-unused-anaconda-packages-and-caches.
• Open OnDemand can not be launched and will show error if your $HOME quota is exceeded.
• If you are not sure if the storage utilization is causing issues for you, you can run ncdu (https://hcc.unl.edu/docs/faq/#how-can-i-check-which-directories-utilize-the-most-storage-on-swan) from the Swan terminal with the location in question.