HTC System Transition to a New Linux Version (CentOS Stream 8)

Starting on August 1, 2022, CHTC’s high throughput computing (HTC) system began upgrading the Linux distribution and version we use on our servers. CentOS Stream 8 is now the operating system used on the majority of our servers, and the default requested operating system by jobs, unless specified otherwise.

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. Users of the HPC cluster will be notified when the transition to CentOS Stream 8 begins on the HPC system.

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

  • August 2022: HTC system will support both CentOS 7 and CentOS Stream 8. By default, all jobs will continue to match to servers running CentOS 7, however, users should begin testing jobs on servers running CentOS Stream 8. These servers are also available for general use.
  • September 2022: More than 75% of CHTC capacity will run on CentOS Stream 8.
  • September 29, 2022: Default operating system requirements for jobs will change from CentOS 7 to CentOS Stream 8.

What You Need to Do

  • If your jobs were running successfully before, but now failing, scale down your submissions and run a few test jobs on the new operating system (now the default). If you absolutely HAVE to keep running, you can continue to (temporarily) run on CentOS 7 by following the instructions below
  • If you are having trouble getting your jobs to run successfully on the new operating system, please contact the facilitation team at or come to office hours
  • If you would like to access as much computing capacity as possible, consider using running your jobs on servers with either CentOS 7 or CentOS Stream 8. See the options below for opting into both; note that your code will likely need to have been compiled on the older operating system version.

Current Status of the HTC System

Capacity Available in the HTC System

Linux Version Percent of Pool Capacity Notable Servers
CentOS 7 33% Build nodes, range of GPU servers, high memory nodes
CentOS Stream 8 67% Build node, servers with A100 GPUs

Default Operating System

By default, CHTC-managed submit servers automatically add a job requirement that requires jobs to run on servers running our primary operating system, CentOS 7, unless otherwise specified by the user. To override this default, see below: Requesting a Specific Operating System.

Requesting a Specific Operating System

At any time, you can require a specific operating system version (or versions) for your jobs.

Use Both CentOS 7 (previous default) and CentOS Stream 8 (current default)

To request that your jobs run on computers running either version of CentOS Linux, add the following requirements line to your submit file:

requirements = (OpSysMajorVer == 7) || (OpSysMajorVer == 8)

Note: this requirement is not necessary for jobs that use Docker containers; these jobs will run on servers with any operating system automatically.

The advantage of this option is that you may be able to access a larger number of computers in CHTC. Note that code compiled on a newer version of Linux may not run older versions of Linux. Make sure to test your jobs specifically on both CentOS Stream 8 and CentOS 7 before using the option above.

Require CentOS 7 (previous default)

To request that your jobs run on servers with CentOS 7 only add the following requirements line to your submit file:

requirements = (OpSysMajorVer == 7)

Combining Requirements

Does your job already have a requirements statement? If so, you can add the requirements above to the pre-existing requirements by using the characters &&. For example, if your jobs already require large data staging:

requirements = (Target.HasCHTCStaging == true) 

You can add the requirements for using CentOS Stream 8 like so:

requirements = (Target.HasCHTCStaging == true) && (OpSysMajorVer == 7)