Kernel panic after dual boot with Kubuntu 14.04 (GRUB) [SOLVED]

First of all, I apologize for the possibly out of place thread.

I have just installed Kubuntu 14.04 LTS on my laptop, alongside Netrunner Rolling, overwriting and older Kubuntu distro (no change in partition scheme). During installation, Kubuntu overwrote GRUB (/dev/sda, MBR), and correctly detected Netrunner Rolling.

However, when I attempt to boot Netrunner (any kernel), I get a kernel panic (“Unable to mount root fs on unknown block (0,0)” ).

I understand that the problem lies with Kubuntu’s GRUB being the older one, and in fact what I want to do is overwrite Kubuntu’s GRUB with Netrunner’s (my original setup and the intended result, but Kubuntu installer forced me into installing bootloader).

My question is, how could I do that without being able to boot into Netrunner? Of course, I could boot a live USB, but I would much rather avoid that, if there is an easier workaround. Is there a way to temporarily fix GRUB, boot into Netrunner and run update-grub from my Netrunner installation?

**** UPDATE ****

Ok, I managed to solve the issue, and here’s how, in case someone else faces the same problem:

I basically followed the solution described in this post by gohlip,

  1. Boot into functioning distro (in my case, Kubuntu)
  2. Open /boot/grub/grub.cfg as root
  3. Pick one of the Netrunner entries and edit the initrd line, which should read something like:
initrd /boot/intel-ucode.img

to the corresponding line found in the grub.cfg of Netrunner’s /boot folder, e.g.

initrd  /boot/intel-ucode.img /boot/initramfs-3.19-x86_64.img

(you could edit all entries, but that would be overkill)

  1. Reboot into the corresponding Netrunner kernel/entry. It should boot OK after the edit.

  2. Once logged in, re-install and update GRUB from Netrunner:

sudo grub-install --recheck /dev/sda  

sudo update-grub

All distros should now boot OK :slight_smile:

No do NOT edit all boot entries.
Netrunner Rolling is based on Manjaro (Arch Linux) and as such it uses grub to load the Intel microcode.
However, in the latest 2015.09 pre-release builds I have removed the Intel microcode from the ISO and thus removing this limitation. I did this to ensure that Netrunner Rolling is more compatible with dual booting other Linux distributions.

Note: Reinstalling the intel-ucode package after installation from these newer ISO’s will result in this limitation returning.

PS. Instead of having to edit your grub config in the manor you described, you can alternatively remove the intel-ucode package from you Netrunner Rolling installation, or make sure you always manage grub from Netrunner Rolling.

That was the original plan, but as I said I ended up overwriting GRUB by accident, and had to find a quick workaround to reboot my system. I do not recommend this process as anything other than a quick fix.