Ubuntu will boot in maintenance mode after the primary disk is unavailable with backup ESP configured

[Yoshi Kadokawa]

I have tested this with the latest Ubuntu Server ISO image, which is Ubuntu 23.04 as of now.
And also updated the subiquity installer when prompted from the installer to 23.04.2.

I have configured the disk layout with one primary ESP partition and a backup ESP partition, and created a software RAID-1 for the root partition.
You can see the details from the attached screenshot.

Installation is perfectly fine, however, after I removed the disk where the primary ESP partition was located (to simulate a disk failure), Ubuntu booted in maintenance mode (will attach the screenshot later).

It get into maintenance mode probably due to EFI partition being mounted via /etc/fstab with the disk UUID specified.

When I continue with the maintenance mode, and check if it can mount all, I get the following error.

$ mount -a
mount: /boot/efi: special device /dev/disk/by-uuid/93CA-9370 does not exist.

And since I have removed that, it is indeed not available. So after updating the /etc/fstab with the backup ESP partition's UUID, it will boot withtout issues now.

It is now much less pain to sync and configure the backup ESP partition, but since we can configure backup ESP partitions from the installer, I was expecting that these kind of small adjustment were not necessary.

[Michael Hudson-Doyle (mwhudson)]

One option would be to mark the ESP mount as nofail in fstab if there is more than one ESP.

A more extreme one would be to stop mounting the ESP at all by default -- grub-multi-install knows where to find them all when they need to be updated.