I have recently tried to upgrade a headless machine following the SDB:System_upgrade page from 15.2 -> 15.3. From previous experience with upgrades I ran in a tmux session to avoid the impact of loss of connection. The connection indeed broke and the system appeared broken after the upgrade. I had to re-perform the upgrade with the installation DVD after which additional configuration and package repairs were necessary.
Is this scenario supported at all? If so, what are the best practices?
As a side-note the machine has an out-of-tree network module injected via DKMS. The module apparently survived the upgrade. Is the behavior of DKMS modules across upgrades documented somewhere?
Yes, this is exactly what I did. The machine is running just fine at this time, I just had to physically wire it up and insert the usb-stick. Also thank you for the info that upgrading headlessly works for you. With hindsight, I did not shut down all demons, especially slurm which has caused me trouble in the past when the queue was inconsistent. Slurm is definitely capable of freezing the system. I will attribute the crash to a failure to shut down relevant services for the moment. Should it turn out to be different when the transition to 15.4 comes, I will try to amend this thread.