Kernel panic - unable to mount root fs after upgrade to 20.04

Question

I got prompted to upgrade to 20.04 on my 19.10 Ubuntu machine. (Linux only, no dualboot) After upgrading, I immediately got presented a white screen saying "Oh no! Something has gone wrong - Please log out and try again". I could not figure out how to log out so I restarted my Notebook.

After restart I got the error:

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) 

I also was not able to use an older kernel via grub, same white error screen appears.

I just reloaded a snapshot with a live-usb.

Is there a way to fix this beforehand? Is something in my current installation broken? I have a pretty basic ubuntu 19.10 installation and expected the upgrade to run smoothly.

I've seen solutions like https://www.geekswarrior.com/2019/07/solved-how-to-fix-kernel-panic-on-linux.html however I did not test them yet. I wanted to use this notebook as consumer-like as possible. So is there any way I configured something wrong beforehand? Or is there any way to officially report this as a bug? Or is it really specific to my notebook-model/setup?

Solution

I had this on every or nearly every update from Ubuntu 19.10 to 20.04. No crazy old devices or anything, just plain VMs or bare metal with standard hardware. So I'm wondering why they obviously didn't even test the happy path of a normal upgrade from 19.10 to 20.04, as it HAS to work on a fresh release, no excuses. "Wait for the first point release" is an advice for the LTS to LTS upgrade.

However, leasts-pain-solution for the people without USB-Sticks at hand is:

• Hold SHIFT during boot to get GRUB menu (it will appear after the first failed boot automatically, though)
• Choose "Advanced options for Ubuntu"
• Choose the older kernel in recovery mode (Linux 5.3.0-51-generic (recovery mode))
• In the Recovery Menu, choose "dpkg - Repair broken packages"
• After repair, reboot. Hold SHIFT again
• Now choose "Advanced options for Ubuntu"/older Kernel again, this time WITHOUT recovery mode
• System should now properly boot with GUI. uname -a will show the old kernel 5.3.0
• Simply reboot again
• System should now magically boot with GUI and the new 5.4.0 Kernel

Comments

[ch1ll]

Thank you for your answer! Ok I didn't know about the first major release update in July! I guess I will just wait for that then. I'm using a Lenovo X230, it's not certified but 19.10 works like a charm. As my Notebook is not certified, I think I won't file a bug report.

[ch1ll]

Thank you for your answer! I just wanted to try it, and gave the update another go... and it just went through. I have no idea why. I got some weird messages on a black screen after the update-process (sorry, I don't remember :/ ) but after a forced restart everything is up and running.

[Duck Dodgers]

So I'm wondering why they obviously didn't even test the happy path of a normal upgrade ... the LTS upgrade is basically a joke. Too many broken things.