[Bug 1791200] Re: grub-pc does not allow preseeding install_devices

[Mathieu Trudel-Lapierre]

A patch is attached, and it's a well-defined problem. Just needs that I
take the patch and test that it behaves correctly to land it.

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

** Changed in: grub2 (Ubuntu)
   Importance: Undecided => High

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https://bugs.launchpad.net/bugs/1791200

Title:
  grub-pc does not allow preseeding install_devices

Status in grub2 package in Ubuntu:
  Triaged

Bug description:
  Background:
  Upon configuration the postinst maintainer script checks to see whether it needs to convert the debconf variable install_devices from the old device name format to the new 'by-id' format. It bases this decision on a version comparison against the "previously installed".

  In a new installation, this comparison is successful since the empty
  version string is older than any other version.

  postinst then goes on to check a few special cases where it can make
  informed decisions on whether the conversion was good without
  involving the user. Failing those checks it forces the debconf
  question to be presented to the user again with the converted device
  ids for confirmation.

  Problem:
  If an administrator has preseeded the install_devices question (using the new 'by-id' format) before installing grub-pc, then the above algorithm incorrectly decides that the user needs to confirm the devices again.

  Solution:
  The attached patch adds another special case that checks if the device IDs where already in the new 'by-id' format and in that case accepts them without asking the user again.

  Versions:
  I have observed this bug for many years, but only now gotten around to tracking it to its source. The patch is against version 2.02-2ubuntu8.4 of grub-pc.

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