[Bug 2054103] Re: grub-pc reinstallation throws a prompt asking the device it should install on for Noble

[Mate Kukri]

To handle upgrades from pre-Noble, u-r-u will likely need a quirk to set
the `grub-{efi,pc}/cloud_style_installation` options if upgrading a
cloud installation.

** Also affects: ubuntu-release-upgrader (Ubuntu)
   Importance: Undecided
       Status: New

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Title:
  grub-pc reinstallation throws a prompt asking the device it should
  install on for Noble

Status in cloud-images:
  New
Status in grub2 package in Ubuntu:
  New
Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  grub-pc requires knowing what device to grub-install on, but when
  cloud images are generated, the device on the deployment target is
  never known. And so when the package is reinstalled (for example, when
  unminimizing the minimized image), the user gets that prompt, asking
  where to install the grub, when this should happen non-interactively,
  for example, by determining where the grub was first installed.

  Interestingly, this issue always existed, however it was masked by the
  following timeline:

  In July 2020, it was discovered that certain scenarios can cause grub-
  pc installation to fail, and an emergency SRU
  https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1889556 disabled
  grub-pc re-installation on upgrade as a workaround.

  Before the commit https://salsa.debian.org/grub-
  team/grub/-/commit/8d809abe752712cb020e2e95fe21d5832bea52f8 got merged
  into Ubuntu, grub-pc/install-devices being unset in debconf was
  acceptable in practice. This was indeed unset and still is for cloud
  images.

  In Dec 2021, grub2 2.06-2ubuntu1 was uploaded containing the
  previously mentioned commit. But as a result of the above emergency
  SRU, that upload managed to silently change the status quo without it
  ever being noticed.

  In December 2023, the grub-pc installation workaround was finally
  removed in
  https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/2043995 exposing
  grub-pc package upgrade failures in cloud images where grub-
  pc/install-devices in debconf was never in-fact set.

  The plausible solution is to develop something to set the grub-
  pc/install-devices debconf entry on first boot in a cloud deployment,
  which would allow upgrades to function like before.

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