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Operating System Upgrade

ICER has upgraded the operating system on all development and compute nodes from CentOS 7 to Ubuntu 22.04. The primary transition for general usage compute nodes occurred on June 17th, 2024.

As part of this process, all software must be rebuilt for the new operating system. This includes all user compiled software, and all software provided by ICER via the module system. ICER has used this as an opportunity to reevaluate software offerings and organization, and as such, the structure of the module system has changed.

Check back for updates!

This page will continue to be updated with new information. Check back regularly for updates.


For specific tasks users need to complete to use the new operating system, please see our page on Preparing for the OS Upgrade.


On June 17

Most nodes are transitioned to the new operating system.

On this date:

  • All development nodes have been moved from CentOS to Ubuntu.
  • The scheduler (SLURM) will briefly be paused.
    • All jobs currently running will continue to run.
    • All jobs in the queue will remain in the queue and be eligible for scheduling when the scheduler is available.
  • All jobs are now submitted to nodes running the new OS by default either with or without the line #SBATCH --reservation=ubuntu_compute.
    • Buy-ins and a small group of nodes will temporarily remain on the old operating system. See our instructions for Submitting to these nodes.
  • All OnDemand apps have been replaced by alternatives that run on the new operating system.
    • Apps running on CentOS will still be temporarily available and will have "(Legacy)" in the title.
On July 17
Buy-in nodes will start being transitioned (unless requested earlier)

Why is this happening?

Operating system upgrade

The HPCC requires operating system updates for similar reasons to a personal computer requiring an operating system upgrade. The current operating system, CentOS 7, was released ten years ago, and is nearing the end of its support. In order to ensure that the HPCC stays secure, operational, and stable, a new, supported operating system will take its place.

ICER has chosen to change Linux distributions from CentOS (or any other Red Hat Enterprise Linux derivative) to Ubuntu. This decision involves many factors, but primary amongst them was the ability to continue using ICER's older nodes, increasing the supply of available compute to our users. From a practical perspective, Ubuntu and CentOS will feel very similar to users, and the majority of commands you may be used to using will still continue to work.

Software upgrade

Behind the scenes, changing a computer's operating system also changes the libraries and programs that the software used on a regular basis relies on. This requires reinstallation of nearly every piece of software to ensure that it is compatible with the new system.

Historically, ICER has a mix of software from a variety of sources, but primarily uses a tool called EasyBuild to install and manage software. To better manage future installations and upgrades, we have used this as an opportunity to reassess which software we can most effectively support. The end result is a software stack better aligned with EasyBuild (which stops supporting older pieces of software) that includes with newer versions that can be tracked and updated more easily.