====== Migration plan ======

<WRAP center round important>
**2026-10-09**: The migration, outlined below, has been completed.
</WRAP>

We will migrate Hábrók to AlmaLinux 9 in a three step procedure. The first step consists of a testing phase, in which some nodes will be made available to the users for testing their workloads on AlmaLinux 9. This is followed by a migration phase, in which compute and user interface nodes will be gradually moved over from AlmaLinux 8 to 9. The final phase is when all nodes have been migrated, including the last user interface nodes.

===== Testing phase =====

**The testing phase has been completed on August 31 2026** The reservation has been removed and the ''merel1.hb.hpc.rug.nl'' test node has been shutdown as ''interactive2.hb.hpc.rug.nl'' has been reinstalled with AlmaLinux 9.

We have made a few nodes available, which are running AlmaLinux 9, to allow users to test their software and workloads. The following nodes are available:

  - Interactive login node ''merel1.hb.hpc.rug.nl''. Users can login to this node and use it in the same way as the other interactive CPU based nodes.
  - Two regular compute nodes called ''vink1'' and ''vink2''. These nodes are CPU based and have 128 cores and 512 GB of memory.
  - Two V100 GPU nodes called ''groenling1'' and ''groenling2'' with 2 Nvidia V100 GPUs.

These nodes have been put in a special reservation called ''alma9_testing''. Jobs can be submitted to this reservation using the following sbatch option: ''%%--%%reservation=alma9_testing''. This can be given on the command line, or using the following ''#SBATCH'' line in your job script:

''#SBATCH %%--%%reservation=alma9_testing''

As you can see from the host names the compute nodes will be named after common birds in the Netherlands, using their Dutch names.

We plan to run this testing phase for three weeks. Please report any issues you encounter while testing the new Alma 9 nodes, so that we can find a way on how to fix these.

===== Gradual migration of compute and login/interactive nodes =====

After the testing phase we will start the migration of the rest of the infrastructure to AlmaLinux 9. This includes the following steps:

  - We will remove the reservation from the existing test nodes and these will become available for all jobs, that do not explicitly request AlmaLinux 8 (see below for details on this)
  - We will migrate ''login2.hb.hpc.rug.nl'', ''interactive2.hb.hpc.rug.nl'' and ''gpu2.hb.hpc.rug.nl'' to AlmaLinux 9.
  - We will migrate the other Hábrók compute nodes to AlmaLinux 9 in batches. Nodes will only be migrated when the running jobs have finished.

==== Submitting explicitly to Alma 8 or Alma 9 nodes ====

If you want to make sure your jobs land on a node with specifically AlmaLinux 8 or 9, you can put a constraint in  your jobs using the sbatch parameter ''%%--%%constraint''. You can either specify ''%%--%%constraint=alma8'' or ''%%--%%constraint=alma9''.

In a job script this would look like:\\

<code>
#SBATCH --constraint=alma8

</code>

Or something similar with ''alma9''.

===== Completing the migration =====

The last steps of the migration will that the last compute nodes will be migrated and the migration will be completed by reinstalling login1.hb.hpc.rug.nl, interactive1.hb.hpc.rug.nl and gpu1.hb.hpc.rug.nl.

After this point all user interface and compute nodes are running AlmaLinux 9.