OS Upgrade on Longleaf: RHEL8 -> RHEL9

Last updated: May 8, 2025

The Longleaf cluster is in process of being upgraded from Red Hat Enterprise Linux version 8 (RHEL8) to RHEL9.

Some codes/workloads will run unaffected on either OS. Some will not. If you have compiled software on R8, we highly recommend recompiling for R9.

Current configuration:

• All jobs submitted to slurm are (by default) directed to RHEL8 resources only
• The majority of compute nodes are still RHEL8
• Using submit script commands, it is possible to submit jobs targeting RHEL9

We recommend testing your codes on RHEL9 at your earliest convenience.

We recommended matching RHEL version of submit/login host to the version of compute nodes targeted.

Choosing RHEL8 or RHEL9

Compute node targeting in your submit script, SBATCH option

--constraint=rhel8 (or no constraint at all)
--constraint=rhel9

If neither are specified, jobs will land on RHEL8 resources

Login/Build hosts

• ssh username@longleaf.its.unc.edu is RHEL8
• ssh username@longleaf-rhel9.its.unc.edu

It remains possible to explicity choose among {8 only, 9 only} using sbatch commands

How long will RHEL8 systems remain available? Currently, most resources are RHEL8, however the set of resources servicing RHEL8 jobs will decrease over time. Please contact us asap to discuss if you are concerned about getting your codes running well on RHEL9.

Which RHEL am I on right now?

cat /etc/redhat-release

can be included in submit scripts

Building code

We recommend explicitly choosing a version of gcc using modules. As of May 2025, the default gcc module version (module load gcc) is 11.2.0 for RHEL8 and 12.2.0 for RHEL9 systems.

"module avail gcc" lists all available versions.

Modules

Troubleshooting tip

Just FYI:

• Help page for prior migration from RHEL7 to RHEL8