[Bug 1848797] Re: After upgrading to 19.10, boot screen shows: "Error: symbol 'grub_file_filters' not found."

[Steve Langasek]

*** This bug is a duplicate of bug 1891680 ***
    https://bugs.launchpad.net/bugs/1891680

A number of upgrade issues were addressed in grub2 2.04-1ubuntu26.4 in
20.04, which was released back in September.  I am going to mark this as
a duplicate of bug #1891680.

However, where the grub debconf state on a system is /wrong/, it is not
possible to guard against this failure on reboot because the running
system cannot know which disk, which is not listed in the debconf state,
has the out-of-date first-stage bootloader.

If you are running an official Ubuntu image in Azure, it should
definitely be in a state that the debconf values are NOT wrong.  Please
open a separate bug report for this and drop a reference to that bug
here.

** This bug has been marked a duplicate of bug 1891680
   grub-pc needs to detect when debconf points to invalid drive and stop in preinst, before unpacking files, and also treat this as a failure in postinst

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https://bugs.launchpad.net/bugs/1848797

Title:
  After upgrading to 19.10, boot screen shows: "Error: symbol
  'grub_file_filters' not found."

Status in grub2 package in Ubuntu:
  Confirmed
Status in grub2 source package in Eoan:
  Confirmed

Bug description:
  After upgrading to 19.10 the boot screen shows the following error:

  Error: symbol 'grub_file_filters' not found.
  Entering rescue mode...

  I could fix it after i booted Ubuntu 19.10 live and used the chroot
  repair method as described here
  https://wiki.ubuntuusers.de/GRUB_2/Reparatur/#chroot-Methode (german)

  Workaround
  ----------
  From https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1848797/comments/18
  "In any case, right now the best thing to do to repair is to boot from a Live image (USB or CD-ROM), and follow the steps in https://help.ubuntu.com/community/Grub2/Installing#via_ChRoot to repair GRUB by hand, or reinstall."

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