I have used Pi Imager to write Ubuntu Desktop to my SD card. When I try to boot from it in my Pi 400, I get the following error:
[50B]: Failed to remount '/' read-only: Device or resource busy systemd-shutdown: Failed to finalize filesystems, ignoring.
and then the Pi shuts down. The first time I booted, I also saw Ubuntu logo and the spinner icon but I can't remember if it was at the very beginning of the boot or just prior to the shutdown (I suspect the latter) but it is no longer showing.
Since I was able to boot into Raspbian from another card, I inserted the Ubuntu card through an USB card reader and both partitions created by Pi imager on that Ubuntu SD card are visible, readable and writable: I was able to create a backup copy of
firstrun.sh and then remove it (as I suspected that it might be causing issues and I also wanted to confirm that the card is writeable).
fsck does not throw any errors for either partition so it looks like filesystem is not corrupted.
What could be the reason the system fails to boot?