Menu entries generated for other linux installations on lvm volumes point to /dev/dm-X as root filesystem which can result in boot failures

Bug #1873924 reported by Jan Rathmann on 2020-04-20
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
grub2 (Ubuntu)
Undecided
Unassigned

Bug Description

Hello,

this is some bug in the generation of grub.cfg that I have seen on all Ubuntu releases during the last years (can't recall when this first happened - sorry!) - now I finally manage to report it :-)

On the grub.cfg generated on my system only the menu entry of my main Ubuntu installation contains a direct reference to the actual name of the volume group/logical volume in the "linux line", e.g.:

...
linux /@/boot/vmlinuz-5.4.0-24-generic root=/dev/mapper/internal--ssd-roothome ro ...
...

This is fine.

But on entries that are generated for linux installations on other logical volumes (which are booted by grub of my main installation) the "linux line" contains only a reference to "/dev/dm-X", e.g.:

...
linux /boot/vmlinuz root=/dev/dm-4
...

The problem is that there seems to be no constant assignment of volume group/logical volume names to "/dev/dm-X" names between reboots, maybe because I have two drives (one SSD with volume group "internal-ssd"; one HDD with volume group "internal-hdd") on my system.
The result is that the menu entries generated this way sometimes fails to boot because "root=/dev/dm-X" points to the wrong logical volume. I can workaround this only by either editing /boot/grub.cfg or editing the menu entries during boot to make them point to the actual name of the logical volume ("root=/dev/mapper/internal--hdd-test1" instead of "root=/dev/dm-0").

So the fix for this issue would be that the entries for other linux installations in grub.cfg would be generated that way that they reference the actual v-group/lv-name of the respective root filesystem instead of volatile /dev/dm-X.

I have attached my grub.cfg below.

Kind regards,
Jan

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: grub2 (not installed)
ProcVersionSignature: Ubuntu 5.4.0-24.28-generic 5.4.30
Uname: Linux 5.4.0-24-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Mon Apr 20 19:01:14 2020
InstallationDate: Installed on 2020-04-08 (12 days ago)
InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Beta amd64 (20200408)
SourcePackage: grub2
UpgradeStatus: No upgrade log present (probably fresh install)

Jan Rathmann (kaiserclaudius) wrote :
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