An overlay for Warewulf 4.x which uses kexec to warm boot into a new node image

Created by Andreas Skau, Research Computing Services, University of Oslo (2026) https://github.com/buzh

cd /path/to/overlays
git clone https://github.com/buzh/wwkexec
wwctl profile edit default # add wwkexec to runtime overlays, default profile just an example - adapt as needed
wwctl overlay build # give it a minute so the new overlays are propagated

ssh <nodename> systemctl start wwkexec.service

With slurm's built-in reboot method we can automatically trigger reloading a new image without interfering with running jobs.

In slurm.conf set:

RebootProgram=/usr/bin/systemctl start wwkexec.service

...or write a wrapper script that takes any additional steps you might need.

Configure the nodes to load a new image, then:

wwctl overlay build (optional but recommended - if you don't, the old image name will be displayed by /etc/issue by default)

scontrol reboot asap <node(s)>

That's it! Sit back and watch the new image be rolled out.