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

[Julian Andres Klode]

** Tags removed: foundations-todo

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Title:
  initrdfail can result in resuming with different initrd images and
  hanging resume

Status in grub2 package in Ubuntu:
  Fix Released
Status in grub2 source package in Bionic:
  In Progress
Status in grub2 source package in Focal:
  Fix Released

Bug description:
  [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?

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