[Bug 1929860] [NEW] initrdfail can result in resuming with different initrd images and hanging resume

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You have been subscribed to a public bug by Matthieu Clemenceau (mclemenceau):

[Impact]
Ubuntu Focal (and new releases) on AWS will normally boot without an initrd image (just the microcode.cpio). There is a fallback mechanism to reboot with the full initrd image when the boot fails to complete. The grub environment variable "initrdfail" is used to track when a boot failed and switch between the optimized initrd-less boot path and the full initrd path.

On a normal successful boot, the "initrdfail" variable is cleared by
grub-initrd-fallback.service. However, this doesn't happen when resuming
from hibernation. As a result, the initrd fallback will get triggered on
the second hibernation / resume cycle despite the original boot using
only the microcode.cpio. This switch in initrd images leads to the
second resume hanging.

We've been able to successfully avoid this issue by adding the following
to the ec2-hibinit-agent resume handler:

/usr/bin/grub-editenv - unset initrdfail
/usr/bin/grub-editenv - unset recordfail

(Note: clearing recordfail may not be necessary, will need to try again
without it.)

This bug was filed against grub2 as it appears to own initrdfail.

[Test plan]
TBD w/ CPC

[Regression potential]
Services get changed to oneshot, and wantedby=multi-user sleep; maybe we miss other places it should run, or record the wrong thing on resume?

** Affects: grub2 (Ubuntu)
     Importance: Critical
         Status: Fix Released

** Affects: grub2 (Ubuntu Bionic)
     Importance: Undecided
         Status: In Progress

** Affects: grub2 (Ubuntu Focal)
     Importance: Undecided
         Status: Fix Released


** Tags: foundations-todo fr-1421 rls-ii-incomings verification-done-focal verification-needed
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initrdfail can result in resuming with different initrd images and hanging resume
https://bugs.launchpad.net/bugs/1929860
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