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

[Max Barry]

Got stuck on this today after upgrading from 19.04 -> 19.10. I do dual-
boot Windows. Also Ubuntu is on a 2-disk mdadm RAID array.

- I couldn't get boot-repair-disk to work: It wouldn't recognize the
internet connection. The LXTerminal it comes with was broken too and
didn't respond to keyboard input, so I couldn't fix it.

- I couldn't install boot-repair from within a live Ubuntu 19.10 USB: It
refused because of an unmet dependency for package boot-sav, even though
I'd added the recommended PPA.

- I did fix it by installing mdadm (sudo apt install mdadm) from within
the live Ubuntu USB, reassembling the RAID array (mdadm --assemble
/dev/md0 /dev/sda1 /dev/sdb1), mounting it, mounting all the other crap
you need to make chroot work, entering chroot, then running update-grub
and grub-install a few times on both disks (grub-install /dev/sda1,
grub-install /dev/sdb1).

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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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