error: symbol 'grub_file_filters' not found [upgrade Ubuntu18.04 to 20.04]

Question

I updated the system from 18.04 to 20.04 via the terminal. When the computer restarts, the black screen appears with the above written mention.

What should I do to fix the problem (without obviously losing the files and programs on the disk)?

Thanks for your help

Answer 1

What DID NOT WORK

1. I had the same issue and above solution by @rapid3642 DID NOT WORK. The CHROOT case was not the right case for me because I could use F12 and able to log in to linux without issue. I also tried running the above commands as chroot on ubuntu system / partition directly ( without the mounting part as I had ubuntu installed and working )
2. Rescatux also did not work although it seems to be the utility which was supposed to be a clean gui.

I used a comment from Kristina Kovacek to get the idea of what we need to do.

What did work for me is the boot-repair-disk utility. Funnily enough it did not work in the default mode ( the Recommended Repair section ) but I had to change following

Advanced Options -> Grub location

1. Change OS to boot by default to the Linux ( yes you can log into windows but you need to keep linux as Master )
2. Untick Spearate /boot /boot/efi partition
3. Place grub into <your linux partition such /dev/sda>

I also removed one other option making sure that by default the GRUB looks into windows I dont remember what it was ( even though I executed the procedure just few moments ago

NOTE that there are instructions that you need to follow and commands that you need to execute manually which also involves purging the grub-install from the linux partition ( which in retrospect might have sufficed. )

Answer 2

Great question, this actually just happened to me and I got it working, I did find some really useful information online and I am happy to share it with you. Being that you asked this a month ago I am sure you are most likely not in the same situation but if you are here is what worked for me.

Firstly I have my Ubuntu 18LTS running inside a VM on a ESXI server. This is the one that had the same issue. I also want to mention that my brother had Ubuntu 18LTS running on a raspberry pi 4 and was able to complete the update to Ubuntu 20LTS without any issues which was great to see.

I found the solution that worked for me at: https://help.ubuntu.com/community/Grub2/Installing#via_ChRoot

I was directed to this by finding the help article posted on: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1848797

I did not have anything raided or complicated on my VM so essentially I could skip a lot of the steps, essentially I followed these steps: Downloaded the same Ubuntu 20 iso from Ubuntu's site (Desktop Image): https://releases.ubuntu.com/20.04/

Then I attached it to my VM and then forced the VM to boot to bios so that I can set the boot priority for a cd first instead of a HDD.

Then I saved and when it rebooted it allowed me to boot from the iso. I then selected the "Try Ubuntu" selection which gets you into the live Ubuntu version.

Then open a terminal and type in:

sudo fdisk -l

this gave me the needed info for the next step. Then you can mount the HDD you have via:

sudo mount /dev/sdXY /mnt

for me the command ended up being

sudo mount /dev/sdb1 /mnt

Then I mounted the critical virtual filesystems, run this as a single command:

for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done

Then Chroot into your normal system:

sudo chroot /mnt

Reinstall GRUB 2:

grub-install /dev/sdX

For me it was:

grub-install /dev/sdb

Recreate the GRUB 2 menu file (grub.cfg):

update-grub

Exit chroot: CTRL-D on keyboard then reboot by using:

sudo reboot