Upgrade from disco to eoan did not preserve the root file system flags which made the system unbootable

[Georgi Georgiev]

I upgraded a raspberry pi 3B+ from disco (installed using the 32-bit bionic image and then upgraded successfully to cosmic and disco) to eoan, but it became unbootable - the initrd was unable to mount the root filesystem.

One caveat of my setup is that I migrated my root filesystem layout from ext4 to raid1 btrfs on two partitions. So in my /boot/firmware/cmdline.txt I had "rootfstype=btrfs rootflags=subvol=@".

After the do-release-upgrade to eoan, cmdline.txt was gone, and the new nobtcmd.txt had the default "rootfstype=ext4" only.

The fix was easy once the issue was clear.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: ubuntu-release-upgrader-core 1:19.10.15
ProcVersionSignature: Ubuntu 5.3.0-1007.8-raspi2 5.3.1
Uname: Linux 5.3.0-1007-raspi2 armv7l
ApportVersion: 2.20.11-0ubuntu8
Architecture: armhf
CrashDB: ubuntu
Date: Tue Oct 22 23:49:35 2019
PackageArchitecture: all
ProcEnviron:
 TERM=screen-256color
 PATH=(custom, no user)
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to eoan on 2019-10-19 (3 days ago)
VarLogDistupgradeLspcitxt:

VarLogDistupgradeXorgFixuplog:
 INFO:root:/usr/bin/do-release-upgrade running
 INFO:root:No xorg.conf, exiting