[Bug 1912677] Re: autogenerated entries for other Ubuntu systems use wrong root filesystem, unbootable

[Akkana Peck]

Wow, really? But if multiple Linux partitions (common since the days of
LILO) are discouraged now, why is os-prober searching for Linux distros
on unmounted partitions and adding them to grub.cfg? If it's just for
Windows and anything else isn't supported, maybe it should only add
Windows installs.

I don't mind adding grub stanzas by hand for distros on other
partitions. But automatically added grub entries that are wrong and
won't boot just clutter the boot menu, making it hard to tell which are
the working entries.

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to grub2 in Ubuntu.
https://bugs.launchpad.net/bugs/1912677

Title:
  autogenerated entries for other Ubuntu systems use wrong root
  filesystem, unbootable

Status in grub2 package in Ubuntu:
  Triaged

Bug description:
  On my disk I have two partitions that are root filesystems for two
  releases, Focal and Groovy:

  Groovy 20.10 is on /dev/nvme0n1p3    3ac2446d-ae7c-4975-b736-44b1084266de
  Focal  20.04 is on /dev/nvme0n1p4    4ff7a630-0e7e-4427-aa9e-513bcae849c3

  If I run update-grub2 from Groovy, it detects the Focal partition and
  generates this entry for it:

  menuentry 'Ubuntu 20.04.1 LTS (20.04) (on /dev/nvme0n1p4)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-simple-4ff7a630-0e7e-4427-aa9e-513bcae849c3' {
  	insmod part_gpt
  	insmod ext2
  	if [ x$feature_platform_search_hint = xy ]; then
  	  search --no-floppy --fs-uuid --set=root  4ff7a630-0e7e-4427-aa9e-513bcae849c3
  	else
  	  search --no-floppy --fs-uuid --set=root 4ff7a630-0e7e-4427-aa9e-513bcae849c3
  	fi
  	linux /boot/vmlinuz-5.4.0-52-generic root=UUID=3ac2446d-ae7c-4975-b736-44b1084266de ro text
  	initrd /boot/initrd.img-5.4.0-52-generic
  }

  Note how the menu correctly says it's on p4, and gives the right UUID
  there and in the search --fs-uuid lines, but then in the actual linux
  kernel line, it uses root=UUID=3ac2446d-ae7c-4975-b736-44b1084266de,
  the wrong partition.

  If I try to boot from that menuentry, the boot fails. At one point I'm
  fairly sure saw a message about not being able to find its initrd
  flash by, but I wasn't able to capture that message. Eventually it
  gets to a single-user prompt, and at that point if I scroll back, here
  are the warnings (yellow) and errors (red) captured in the scrollback:

  UNSUPP Starting of Executable File Format File System Automount Point not supported
  FAILED Failed to mount /boot/efi
  DEPEND Dependency failed for Local File Systems

  If I give the root password and then type mount, it has /dev/nvme0n1p3
  (the Groovy root) mounted on /, not p4 (the Focal root it should be
  using).

  So if I want to be able to use that Focal partition, I can't use the
  entry generated by os-prober; I have to make my own entry and add it
  to somewhere like 40_custom (in reality, of course I want it earlier,
  before the nonworking os-prober entries, so I named it 25-local):

  menuentry 'Ubuntu 20.04 Focal LTS on nvme0n1p4' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-4ff7a630-0e7e-4427-aa9e-513bcae849c3' {
  	recordfail
  	load_video
  	gfxmode $linux_gfx_mode
  	insmod gzio
  	if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
  	insmod part_gpt
  	insmod ext2
  	if [ x$feature_platform_search_hint = xy ]; then
  	  search --no-floppy --fs-uuid --set=root  4ff7a630-0e7e-4427-aa9e-513bcae849c3
  	else
  	  search --no-floppy --fs-uuid --set=root 4ff7a630-0e7e-4427-aa9e-513bcae849c3
  	fi
  	linux	/boot/vmlinuz-5.4.0-52-generic root=UUID=4ff7a630-0e7e-4427-aa9e-513bcae849c3 ro  text
  	initrd	/boot/initrd.img-5.4.0-52-generic
  }

  ProblemType: Bug
  DistroRelease: Ubuntu 20.10
  Package: grub-common 2.04-1ubuntu35.1
  ProcVersionSignature: Ubuntu 5.8.0-38.43-generic 5.8.18
  Uname: Linux 5.8.0-38-generic x86_64
  ApportVersion: 2.20.11-0ubuntu50.3
  Architecture: amd64
  CasperMD5CheckResult: skip
  Date: Thu Jan 21 10:26:38 2021
  InstallationDate: Installed on 2020-04-29 (267 days ago)
  InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
  SourcePackage: grub2
  UpgradeStatus: Upgraded to groovy on 2020-10-23 (90 days ago)
  mtime.conffile..etc.grub.d.10_linux: 2021-01-21T10:19:44.446687

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1912677/+subscriptions