My NAS is currently running Ubuntu 22.04.5 LTS. I have tried in the past to perform a do-release-upgrade, and ended up with a system that will not boot.
Since then, I have moved many services away from the NAS. I thought I should give it one more try, and I did just that yesterday. Unfortunately the result ended up the same, resulting another rescue.
I thought I should document the rescue process here again.
# Wipe the root fs
mkfs.ext4 /dev/nvme1n1p2
# Restore from backup
mount /dev/nvme1n1p2 /mnt
mount /dev/backup_partition /mntb
rsync -aAXv /mntb/ /mnt/
# Ensure the root file system new UUID is the same in /etc/fstab
vi /mnt/etc/fstab
# chroot to install the boot partition
mount /dev/nvme1n1p1 /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do mount -B $i /mnt$i; done
mount -t efivarfs efivarfs /mnt/sys/firmware/efi/efivars
chroot /mnt
# Identify your EFI partition again just in case (e.g., /boot/efi)
sudo grub-install
# Below is more forceful but mostly optional and unnecessary
# grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB --removable --recheck
sudo update-grub
exit
# Exit and reboot
umount -l /mnt
reboot
By now I have become an expert in rescuing failed upgrades with Ubuntu.
I have upgraded my TUF GAMING B550-PLUS motherboard to version 3636. This is a recently released BIOS from ASUS in January of 2026. My previous version of the BIOS was from 2024.
I will give myself another breather, say about a week, before attempting to try again.