Cilium Issues With Ubuntu 25.10 On RPi5

Recently, I was trying to be better about IT housekeeping in my homelab and upgraded my RPi 5 RKE2 nodes from Ubuntu 25.04 to 25.10. This turned out to be quite a mistake at present. Over the next couple days I saw nodes randomly go NotReady for no detectable reason. The nodes wouldn’t respond over SSH so a hard reset was tried. This got the node to come back for a little while but it would go offline again after a few hours. Reviewing the logs from journald it looked like network traffic was just…stopping all of a sudden and not coming back. Looking around online I found this Github bug which pointed to the issue being a driver problem in kernel 6.17. There were no updated kernels available and no further workarounds except using a watchdog to reload the network driver that I could find. Having all of my network shares drop out from underneith my pods seemed like a bad thing so I went exploring other options.

Luckily, a quick check of all of my nodes showed that I still had the older (working) 6.14 kernel installed. All I had to do was figure out how to make the RPi boot it. After a bit of fussing and a few false steps I came up with the following: edit /boot/firmware/config.txt so that the first os_prefix line looks like this.

[all]
#os_prefix=current/
os_prefix=old/

A quick reboot later and uname -a is reporting the right kernel version. Time will tell if this fix is sufficient but for the moment signs look good. I’m not sure if this fix will survive another kernel update but I am guessing that making a copy of the old/ directory and any of its linked files would let me roll back by repointing config.txt again. I’ll keep this post updated as I find anything further or fixes become available.