Some time ago (more than a year ago) one of my computers failed to boot after an update (note - not a kernel update. A @world update.) I couldn't figure out why and installed grub2 and used UUIDs as a temporary fix.
I got a new SSD for that machine today, so I went and moved everything over, then (of course) it wouldn't boot any longer, and I remembered my kludge and spent some time finally figuring out the cause. It appears to be udev. Somewhere along in its stupid detection it decides to process USB devices before sata ports, thusly randomly renaming the boot drive to something else in the process. It took me forever to figure this out, I eventually had a lightbulb moment and used my phone to record video of it booting, then slowing it down, as when the kernel panics you can't scroll back up to see WTF happened. This is an older machine, but I'm not convinced it's the motherboard doing this. I've checked the boot order in the BIOS. I've also tried setting and unsetting "BIOS order determines boot disk" in the kernel config and it made no difference. What eventually fixed it was building USB as modules. (Another kludge!) I have no custom udev rules, the only rules I could find were in /lib/udev/rules.d: 10-dm.rules 11-dm-lvm.rules 13-dm-disk.rules 40-gentoo.rules 50-udev-default.rules 60-block.rules 60-cdrom_id.rules 60-drm.rules 60-evdev.rules 60-persistent-alsa.rules 60-persistent-input.rules 60-persistent-storage-tape.rules 60-persistent-storage.rules 60-persistent-v4l.rules 60-serial.rules 64-btrfs.rules 69-dm-lvm-metad.rules 70-infrared.rules 70-mouse.rules 70-udev-acl.rules 75-net-description.rules 75-probe_mtd.rules 78-sound-card.rules 80-drivers.rules 80-net-setup-link.rules 80-udisks.rules 90-alsa-restore.rules 90-network.rules 95-dm-notify.rules 99-nvidia.rules Does anyone have any explanation for this daft behaviour or know where I should look? I have multiple machines and it's only this one that has this problem, which happened after a @world update long ago. Dan
