That did the trick. I guess qubes didnt like me trying to delete a volume it thought was in active use.
Here’s the whole fix procedure:
- on a separate computer, burn a debian installation image to a USB drive
- on the affected PC, reboot and use BIOS to boot from the USB drive
- open “rescue mode” on the live USB installer
- decrypt the qubes encrypted partition with LUKS (the debian rescue image prompted me automatically to do this)
- run
sudo lvremove /dev/qubes_dom0/vm-sys-usb-private-snap - reboot
In theory i didn’t even need to do the qubes.skip_autostart or muck with systemd at all, as removing this logical volume is what allowed the sys-usb qube to finally start.
Seems like this is something that qubes should be able to handle automatically on boot, no?