[Bug 1754586] Re: [FFe request] Enable booting initrd-less with fallback

[Mathieu Trudel-Lapierre]

Landed in grub2 2.02+dfsg1-5ubuntu5.

** Changed in: grub2 (Ubuntu)
       Status: Triaged => Fix Released

-- 
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/1754586

Title:
  [FFe request] Enable booting initrd-less with fallback

Status in grub2 package in Ubuntu:
  Fix Released

Bug description:
  The proposed change allows users to enable "initrd-less" boot for
  kernels that support it, by setting the GRUB_FORCE_PARTUUID
  configuration variable in /etc/default/grub.

  In case the user sets the variable today, the initrd line will not be
  written, and some kernels will boot this way (faster, usually, since
  there is no IO involved to lift the initrd from disk. This is
  particularly relevant to cloud images for example).

  This change allows the GRUB_FORCE_PARTUUID to be set more agressively,
  by providing a fallback mechanism: should the initrd-less boot fail,
  grub will try booting the same kernel with an initrd. To achieve this
  we set a flag in grubenv, that is then cleaned very early in the
  userspace boot process.

  The rest of the behavior does not change.

  Users not using initrd-less boots are unaffected by this change.
  Users currently using initrd-less boots will still boot - and get a new fallback in case the kernel they boot does not support initrd-less booting (when upgrading or changing kernel flavor for example).

  Testing done:

  - Booting with and without initrd on a kernel that supports it (in this particular case the -gcp kernel)
  - Booting with and without initrd on a kernel that does *not* support it (ensuring the fallback works)
  - Tried to test the case where userspace sets "next boot" but it looks like the feature allowing to do so regressed. This is independent of this FFe and will be the subject of another bugreport (it's mentioned here since tangentially relevant).

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1754586/+subscriptions