HTC System Transition to a New Linux Version (CentOS Stream 9)

Starting in March 2024, CHTC’s high throughput computing (HTC) system began upgrading the Linux distribution and version we use on our servers to CentOS Stream 9. This transition is expected to complete in May 2024.

Note that this page only applies to a transition on the HTC system (submitting jobs with HTCondor). The high performance computing (HPC) cluster will be upgraded in the near future as well and have a separate transition page.

All updates to the HTC system will be reflected on this page; significant changes may also include a notification to the chtc-users mailing list.

Important Dates

Note: By default, CHTC-managed submit servers automatically add a job requirement that requires jobs to run on servers running our primary operating system unless otherwise specified by the user.

• April 2024: HTC system will support CentOS 7, CentOS Stream 8, and CentOS Stream 9. By default, all jobs not using a software container will continue to match to servers running CentOS 8, however, users should begin using software containers or testing jobs on servers running CentOS Stream 9.
• May 1, 2024: Default operating system requirements for jobs will change from CentOS 8 to CentOS Stream 9.
• May 31, 2024: No more CentOS8 servers remain in the HTC system.

What You Need to Do

If your jobs use containers (Docker, Singularity/Apptainer)

No action is needed for researchers already using a Docker or Singularity/Apptainer software containers in their jobs. Because software containers have a small operating system installed inside of them, these jobs carry everything they need with them and do not rely signifcantly on the host operating system. By default, your jobs will match to any operating system in the HTC pool, including the new CentOS Stream 9 hosts.

All other jobs (not using containers)

Researchers not already using a Docker or Apptainer software container will need to either

• (a) test their software/code on a CentOS Stream 9 machine to see their software needs to be reinstalled. See Transition to New Operating System.
• or
• (b) switch to using a software container (recommended). See below for additional information.

If you would like to access as much computing capacity as possible, consider using a Docker or Apptainer software container for your jobs so that your jobs can match to a variety of operating systems. See the information below for detailed instructions on creating and using software containers.

If you are unable to test or transition your jobs to CentOS Stream 9 before May 1st, there is an option to opt into CentOS Stream 8 for the short term. See Transition to New Operating System.

Options For Transitioning Your Jobs

1. Use a Container (recommended)
2. Transition to New Operating System

Option 1: Use a Software Container (Recommended)

Using a software container to provide a base version of Linux will allow you to run on any nodes in the HTC system regardless of the operating system it is running, and not limit you to a subset of nodes.

CHTC provides helpful information for learning about creating and using Docker and Apptainer software commands:

Apptainer

• Use Apptainer Containers
• Build an Apptainer Container
• Advanced Apptainer Example - SUMO

Docker

• Explore and Test Docker Containers
• Build a Docker Container Image
• Running HTC Jobs Using Docker Containers

CHTC users are welcome to reach out to the Facilitation team via email or in office hours for help installing their software into a container.

Option 2: Transition to a New Operating System

This option is more limiting because you are restricted to operating systems used by CHTC, and the number of nodes running that operating system.

Researchers that do not wish to use containers for their job should test their jobs on the CentOS Stream 9 machines as soon as possible so that jobs are not significantly disrupted by this transition. We recommend:

• Test your jobs by requesting the new operating system (chtc_want_el9 = true, see more details below) for 1-2 test jobs. (Note that after May 1, this option will not be required as CentOS Stream 9 will be the default.)
• If needed, recompile your code.

Note that if you have not tested your code by May 1, you may want to opt into CentOS Stream 8 temporarily until you have tested and transitioned your code. Instructions for requesting a specific operating system(s) are outlined here:

• Use Custom Linux Versions in CHTC

If you are having trouble getting your jobs to run successfully on the new operating system, please contact the facilitation team at chtc@cs.wisc.edu or come to office hours