[Bug 1885571] Re: Can't set boot kernel in GRUB on focal image

[Philip Roche]

** Also affects: grub (Ubuntu)
   Importance: Undecided
       Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to grub in Ubuntu.
https://bugs.launchpad.net/bugs/1885571

Title:
  Can't set boot kernel in GRUB on focal image

Status in cloud-images:
  New
Status in grub package in Ubuntu:
  New

Bug description:
  It appears that the 20.04 cloud image does not update-grub properly
  when GRUB_DEFAULT is changed.

  As part of my livepatch testing process, I will install an older
  kernel release on a cloud image, and then set the image to boot the
  older kernel, which is how I noticed this problem. However, the bug is
  reproducible without installing anything.

  Steps to reproduce:
  1. create a new focal VM using 'uvt-kvm create test release=focal arch=amd64'.
  2. SSH into the new VM using 'uvt-kvm ssh test'.
  3. Change the default boot entry to boot the installed kernel using the advanced menu, by using this command:

    echo "GRUB_DEFAULT='Advanced options for Ubuntu>Ubuntu, with Linux
  $(uname -r)'" | sudo tee /etc/default/grub.d/99-override-kernel.cfg

  4. Update the grub files using 'sudo update-grub'.
  5. Reboot the VM using 'sudo reboot'.

  WHAT I EXPECTED:
  The VM should reboot into the specified kernel. This does work correctly on bionic and xenial VMs.

  WHAT HAPPENED:
  The VM fails to boot. Instead, it crashes in an infinite loop.

  [    1.451958] VFS: Cannot open root device "PARTUUID=f1fd35e8-b25d-4dea-8e33-06fc04e8fcdf" or unknown-block(0,0): error -6
  [    1.454532] Please append a correct "root=" boot option; here are the available partitions:
  [    1.456671] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
  [    1.458372] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-39-generic #43-Ubuntu
  [    1.459935] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1 04/01/2014
  [    1.461705] Call Trace:
  [    1.462312]  dump_stack+0x6d/0x9a
  [    1.463064]  panic+0x101/0x2e3
  [    1.463917]  mount_block_root+0x23f/0x2e8
  [    1.464786]  mount_root+0x38/0x3a
  [    1.465595]  prepare_namespace+0x13f/0x194
  [    1.466503]  kernel_init_freeable+0x231/0x255
  [    1.467448]  ? rest_init+0xb0/0xb0
  [    1.468213]  kernel_init+0xe/0x100
  [    1.469061]  ret_from_fork+0x35/0x40
  [    1.471399] Kernel Offset: 0x2ce00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
  [    1.474038] ACPI MEMORY or I/O RESET_REG.

To manage notifications about this bug go to:
https://bugs.launchpad.net/cloud-images/+bug/1885571/+subscriptions