grub_file_filters not found after Ubuntu 19.10 upgrade

In my case, I had an Xubuntu 18.04 VM and after upgrading to 20.04, got the grub error. So I followed what's described here, which is for Kali, but should work for any Linux / grub installation:

1. Using an Ubuntu / Xubuntu ISO Live enter live mode (I used Ubuntu 20.04 since I had it already downloaded in my computer).

2. Once inside, I opened a terminal and ran:

# So we can run the next commands as `root`:
sudo su

# To figure which partition had my Xubuntu installation (partition type `Linux`)
# in my case it was `/dev/sda1`, we can use:
fdisk -l

# Let's mount a few things:
mount /dev/sda1 /mnt
mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys

chroot /mnt

# Now let's try to fix Grub:
grub-install /dev/sda

If things went well, you should see a message saying something like:

Installation finished. No error reported

3. Now we can cleanup and reboot:

# To change back chroot:
exit

# And now we can umount all:
umount /mnt/dev/pts
umount /mnt/dev
umount /mnt/proc
umount /mnt/sys
umount /mnt

# Now we can reboot:
reboot

Got the same issue, fixed by booting a 19.10 "rescue" USB key then, in terminal: (where sda is your disk and sda1 is your partition on the disk.)

$ sudo mount /dev/sda1 /mnt
$ sudo grub-install --root-directory=/mnt /dev/sda

I couldn't get boot-repair (or boot-repair-disk) working, but managed to fix this by booting from a live Ubuntu 19.10 USB, mounting the old disk, entering chroot, and running grub-install and update-grub.

There is a launchpad bug here, which recommends the chroot fix as described here.

I had exactly the same problem about a week ago. I solved it by downloading the boot-repair-disk from sourceforge. You will need to manufacture a bootable USB key or CD if you have a suitable CD drive. There are plenty of guides online about how to do this. I hope you have access to a system where you can do it. You can do it on Windows.

It may be possible to fix it from the grub rescue prompt and then the grub prompt. I tried this first but didn’t have success following a guide I found online.

Good luck

I too encountered the exact same problem after updating to Ubuntu 19.10. Here is how I (just now) resolved it:

First, you have two problems, not one. Both your installation is screwed up and the Grub Bootloader is messed up. And running only one fix won't fix everything. You need both the "boot-repair-disk" and the latest version of Ubuntu (both on USB boot drives. Don't use a DVD.)

If you try to do (only) a "Repair Install" from the Ubuntu Live disk first, you'll still be greeted by the "grub rescue>" prompt when done. :( So, first you must use the "boot-repair-disk". Tell it to repair your broken boot partition with Ubuntu on it. If you aren't sure of the partition ID, launch "GParted" from the "Start" menu (bottom left.)

Repair that boot partition. This should at least bring Grub back. Try to launch Ubuntu. If it works, you're done. If not, boot the Live "CD" from USB.

Double-click the "Install Ubuntu 19.10" icon on the desktop (don't worry, there will be an option to repair w/o losing your old programs/files.)

I recommend checking the boxes to download all updates during install, including 3rd party.

The Installer should detect your broken partition and give you the option to repair it (the first option.) It may need to disable some 3rd party repositories. Not a big deal, they're easy enough to get back later.

(Note: If you had to login with a password before, don't try to select "login w/o password" now. It won't let you in when you're done.)

Once done, you should have Ubuntu 19.10 installed with all/most of your existing apps still installed (though the toolbar shortcuts will be reset.) I had to reinstall a few 3rd party apps, but their configurations were still there afterwards, so nothing was lost.