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

[Mate Kukri]

*** This bug is a duplicate of bug 508901 ***
    https://bugs.launchpad.net/bugs/508901

It seems like this issue is a lot older then expected and has a
duplicate from 2010 :)

** This bug has been marked a duplicate of bug 508901
   update-grub sets wrong root argument

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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

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