[SOLVED] Won't boot after update to 5.15.0-76-generic

[SteveTaylor]

After the latest update to 5.15.0-76-generic my computer won't boot. If I select the 5.15.0-75-generic kernel, it boots okay. How can I determine what is causing this failure?
Can I revert back to the 75 kernel?

[dejjanku]

Did automated update broke it?

I think that is the biggest issue that automated update is breaking install regardless of kernel in question, but previous similar topic is marked as solved...

[Snowhog]

Can I revert back to the 75 kernel?

You can tell Grub which installed kernel to use as 'default'. Installed kernels are counted starting with 0 (zero) being the 'latest' installed kernel. The first prior installed kernel is number 1, the second prior installed kernel is number 2, etc.

You can edit /etc/default/grub (sudo nano /etc/default/grub or launch Kate and open /etc/default/grub) and change the number value in GRUB_DEFAULT= (which is/should be 0) to 1 (GRUB_DEFAULT=1). Save the changes (if editing using Kate you will be prompted for your password). Once the file is saved, you need to update grub. Open Konsole (if you aren't already in it) and type: sudo update-grub2

Logout and reboot.

[Schwarzer Kater]

A slight correction (sorry Snowhog ):

GRUB_DEFAULT=N in your /etc/default/grub does not specify the kernel (number) but the Nth entry in the generated menu counted from 0 (this is an important difference).

It also does not take submenus into account - unless you specify this explicitely with GRUB_DISABLE_SUBMENU=true .

[Snowhog]

A slight correction (sorry Snowhog ):

Not a problem.

Contrary to my own opinion, I'm not always right!

[Schwarzer Kater]

After the latest update to 5.15.0-76-generic my computer won't boot. If I select the 5.15.0-75-generic kernel, it boots okay. How can I determine what is causing this failure?
Can I revert back to the 75 kernel?

Can you describe what exactly does happen?

Can you spot something in you sudo journalctl -b -1 -a after you have (unsuccessfully) tried booting with 5.15.0-76-generic and immediately afterwards successfully booted with 5.15.0-75-generic?

---

If I temporarily wanted to make 5.15.0-75-generic my default kernel for a period of time (e.g. until I solved the problem with 5.15.0-76-generic myself or a later kernel, let's call it 5.15.0-77-generic, would solve the problem for me), I would at first mark the 5.15.0-75-generic kernel as manually installed so it would not be erased by any future kernel update:
1. In Konsole
sudo apt-mark manual linux-{headers,image,modules,modules-extra}-5.15.0-75-generic

Then I would alter my /etc/default/grub to always automatically boot from the last entry I chose (which of course would be kernel 5.15.0-75-generic in this case) - even from a submenu entry:
2a. In Konsole
sudo cp /etc/default/grub /etc/default/grub.orig (to make a copy of your GRUB settings so you can easily revert them if anything goes wrong or the kernel issue has been resolved and you want to go back to GRUB's old behaviour)

2b. Open /etc/default/grub in Kate (or use e.g. nano or vim in Konsole if you would prefer that) and modify it accordingly:

GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=1

In GRUB_TIMEOUT= choose any amount of seconds you want GRUB to wait until it automalically boots from the pre-chosen entry (-1 will make GRUB wait indefinitely).

Don't forget to sudo update-grub in Konsole afterwards and reboot.

3. Now immediately press e.g. an arrow key or [Space] when you see the GRUB boot menu and the timer of 1 second will stop and let you choose the boot menu entry you want to boot from (the 5.15.0-75-generic kernel in your case).

In the future you will always automatically boot from the 5.15.0-75-generic kernel until you choose another entry in the GRUB boot menu which will then stay the default until you choose another …


If you wanted to revert the process (e.g. because you solved the problem or a newer kernel has been released that does not cause the problem anymore):

1. Mark the 5.15.0-75-generic kernel as automatically installed again:
In Konsole
sudo apt-mark auto linux-{headers,image,modules,modules-extra}-5.15.0-75-generic

2. Revert GRUB to the default *Ubuntu behaviour again (optional - you could also leave this as you changed it if it suits your needs better):
In Konsole
sudo cp /etc/default/grub.orig /etc/default/grub
sudo update-grub

Reboot.

[SteveTaylor]

When I tried sudo journalctl -b -1 -a it was a long output with a few warnings ut the last three lines were:

Jul 03 09:28:38 steve-i5 systemd[1]: Starting Time & Date Service...
Jul 03 09:28:38 steve-i5 sddm[911]: Failed to read display number from pipe
Jul 03 09:28:38 steve-i5 sddm[911]: Could not start Display server on vt 1

The last two were in red.

I have marked the 75-generic as manual and set GRUB to saved.
Now I see there are updates available so I'll do those and then see what happens.

[SteveTaylor]

Those latest updates had some nvidia updates and now by computer boots with the 76 kernel just fine.