piKVM is amazing. I had one controlling an old desktop of mine for over 18 months with no issues. I decided to update its software and ran into some problems.
The first problem was pacman was returning a 404 when trying to update. I guess in the last year and a half the repository URL had changed. I had to edit
/etc/pacman.conf and update the URL:
[pikvm] Server = https://files.pikvm.org/repos/arch/rpi4 SigLevel = Required DatabaseOptional
After fixing that, running pacman -Syu and answering yes, I rebooted, but found that kvmd would not start. The first symptom: HTTP 500 from nginx. Digging in I found that two services were failing to start: kvmd-tc358743.service and kvm-otg.service.
v4l2-ctl: Cannot open device /dev/kvmd-video, exiting
kvmd-otg: RuntimeError: Can't find any UDC
With these two services bailing the web UI wouldn’t start. I checked the kernel log and the tc358743 device was not detected at all. I was about to give up and just reflash the device when I noticed two files in /boot: cmdline.txt.pacsave and config.txt.pacsave. I know from my experience in arch that it means I had some configurations get clobbered. Running a diff between the two I found some very important lines omitted:
I restored the .pacsave files and rebooted, and it worked! Everything came back.
Next time I won’t wait so long between software updates.