Dual-boot Arch + Ubuntu. Both kernels panic after reinstalling bootloaders on a shared EFI partition

[awannabetheone]

Hi everyone,
I've been trying to recover my dual-boot setup, but I'm now stuck in a situation where both Arch and Ubuntu fail to boot.
System:
Lenovo ThinkPad T14 Gen 2 (AMD Ryzen 5 PRO 5650U)
UEFI mode
GPT partition table
Partitions:
nvme0n1p1 EFI System Partition (FAT32)
nvme0n1p2 Ubuntu 26.04
nvme0n1p3 Arch Linux
What happened:
My EFI partition became corrupted, so I reformatted the ESP.
Reinstalled Arch's bootloader.
Regenerated initramfs.
Fixed Arch's UUIDs.
Arch successfully booted into Hyprland.
Then I reinstalled Ubuntu's GRUB:
grub-install
update-grub
Ubuntu was missing its kernel files, so I reinstalled:
linux-image-7.0.0-27-generic
linux-image-generic
This recreated:
vmlinuz-7.0.0-27-generic
initrd.img-7.0.0-27-generic
What I have already verified:
UUIDs from blkid match /etc/fstab.
GRUB uses the correct root UUID for Ubuntu.
update-grub successfully detects both Ubuntu and Arch.
efibootmgr -v shows valid entries for both Ubuntu and Arch.
Ubuntu kernel and initrd now exist.
Current symptoms:
From GRUB:
Ubuntu -> Kernel panic
VFS: Unable to mount root fs on unknown-block(0,0)
Arch -> Kernel panic
From UEFI Boot Menu:
Ubuntu -> Same kernel panic
Arch -> Immediately returns to firmware Boot Menu.
One thing that looks strange is that my shared ESP now contains both kernels:
vmlinuz-linux
vmlinuz-7.0.0-27-generic
EFI/
loader/
During Arch installation I mounted the ESP as:
/boot
Ubuntu uses the same ESP.
At this point I'm unsure whether this is:
a GRUB configuration problem,
an initramfs issue,
an ESP layout problem,
or something else.
Has anyone seen a situation where both operating systems panic after rebuilding bootloaders on a shared EFI partition?

 

[Alexzee]

No, I haven't seen what you have going on.

Maybe try fsck with a Live version of Arch via a usb on both systems.
Then reboot.

Reinstalling the kernel for Ubuntu most likely created issues and didn't sync up with what the fstab file contains. IF you didn't include the headers that will make it hard for Grub also. Have a look at the fstab file and compare it to the uuid's.

Any idea on how your EFI partition became corrupted?
Did you have a unexpected inconsistancy?
And do you have all of the grub config files for Arch and Ubuntu?

Missing kernel files will cause the bootloader to not function because if Grub doesn't know about the kernel and config it won't boot the distribution.

There is a script called 'bootinfoscript'. It's really helpful with getting the info. that you need when there are booting issues.

If I were you, I'd run it and read through it to get clues.

Boot Info Script

Download Boot Info Script for free. Boot Info Script is a bash script which searches all hard drives attached to the computer for information related to booting. Its primary use is for troubleshooting booting problems.

sourceforge.net

SourceForge.net: Boot Info Script - Project Web Hosting - Open Source Software

Boot Info Script is a bash script which searches all hard drives attached to the computer for information related to booting and displays it in a convenient format. Its primary use is for troubleshooting booting problems.

bootinfoscript.sourceforge.net

Post it (Results.txt) if your not sure and I'll read it when I can.

Last thoughts:
Pacman deletes the old kernel files from your root partition. It then writes the new vmlinuz and initramfs images into the bare /boot directory on your root drive instead of your actual boot partition. I'm thinking that why you have both vmlinuz images.

Our members @Condobloke, @wizardfromoz and @CaffeineAddict are talented when working with Grub.

 

[awannabetheone]

ESP is readable and not obviously corrupted.
Both Ubuntu and Arch kernels exist in /boot.
Ubuntu fstab UUID matches blkid.
update-grub detects both Ubuntu and Arch.
Both entries still end in kernel panic.
Arch was booting correctly before Ubuntu was repaired.
Both distributions share the same EFI System Partition. do you have an idea what's going on with this?

 

[Alexzee]

ESP is readable and not obviously corrupted.
Both Ubuntu and Arch kernels exist in /boot.
Ubuntu fstab UUID matches blkid.
update-grub detects both Ubuntu and Arch.
Both entries still end in kernel panic.
Arch was booting correctly before Ubuntu was repaired.
Both distributions share the same EFI System Partition. do you have an idea what's going on with this?

My EFI partition became corrupted, so I reformatted the ESP.

Just quoting what you said from your first post.

Are you sure that the UUID in the fstab file matches what Grub points to?
Have you looked at the previous boot logs?
It should show what (if kdump was running) what the kernel was doing and the moment the panic hit, what modules were loading and what tipped it over.

And to answer your question: no, without seeing the results of the bootinfo script I'm not able to tell you what is going on with your system.
What I can tell you is that your configuration got botched. No if and's, but's or coconuts about that:-

 

[Alexzee]

An education to say the least.

Identifying Kernel Panic Causes and Troubleshooting Steps

Master essential techniques for diagnosing and resolving a kernel panic to ensure your Linux environment operates without disruptions.

linuxsecurity.com

 

[awannabetheone]

hgJust quoting what you said from your first post.

Are you sure that the UUID in the fstab file matches what Grub points to?
Have you looked at the previous boot logs?
It should show what (if kdump was running) what the kernel was doing and the moment the panic hit, what modules were loading and what tipped it over.

And to answer your question: no, without seeing the results of the bootinfo script I'm not able to tell you what is going on with your system.
What I can tell you is that your configuration got botched. No if and's, but's or coconuts about that:-

Thanks for taking a look.
I have already verified that Ubuntu's /etc/fstab UUID matches the output of blkid, and grub.cfg also points to the same root UUID.
The ESP was reformatted because it became corrupted, then I restored the bootloaders.
Ubuntu's kernel (vmlinuz-7.0.0-27-generic) and initrd are present in /boot, and Arch's vmlinuz-linux is also present.
update-grub detects both Ubuntu and Arch successfully.
However, both entries still end in a kernel panic.
I'll run the Boot Info Script and post the Results.txt here.