[SOLVED] Problems with new multiboot distro: You must first load the kernel"

[Dan-cer]

I just installed another distro (Debian 13), alongside KDE neon and Feren OS (also KDE). During installation, I checked the "bootable" box. I probably shouldn't have done that, because Debian ended up creating its own bootloader with Grub. I have now partially corrected this, and the previous Grub of my default OS is displayed again. Debian is also listed.
However, when I select Debian, the following error message appears:

Error: File "/boot/vmlinuz-xxx-amd64 not found.
Error: You must first load the kernel

How can I fix that?

[oshunluvr]

The grub stanza is wrong for some reason. The first thing to run "sudo update-grub" then look through /boot/grub/grub.cfg and see if it fixed it.

Otherwise, if you want help you'll need to provide more details like where Debian is installed, the list of files in it's /boot/ folder, and the grub stanza relating to Debian, for starters.

[Dan-cer]

Yes sure.

lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 572K 1 loop /snap/color-picker/26
loop1 7:1 0 4K 1 loop /snap/bare/5
loop2 7:2 0 63,8M 1 loop /snap/core20/2669
loop3 7:3 0 63,8M 1 loop /snap/core20/2682
loop4 7:4 0 73,9M 1 loop /snap/core22/2139
loop5 7:5 0 91,7M 1 loop /snap/gtk-common-themes/1535
loop6 7:6 0 373,4M 1 loop /snap/qt5-core20/24
loop7 7:7 0 63,1M 1 loop /snap/hplip-printer-app/925
loop8 7:8 0 50,9M 1 loop /snap/snapd/25577
sda 8:0 0 238,5G 0 disk
├─sda1 8:1 0 140,6G 0 part /mnt/b73f5c2a-b805-4d7c-ba15-36c09afc1e7
7
└─sda2 8:2 0 97,8G 0 part /
sr0 11:0 1 1024M 0 rom
nvme0n1 259:0 0 476,9G 0 disk
├─nvme0n1p1 259:1 0 2,2G 0 part /boot/efi
├─nvme0n1p2 259:2 0 58,7G 0 part /mnt/67a34737-e209-490c-964d-3c594734b07
0
├─nvme0n1p3 259:3 0 175,8G 0 part /mnt/f3c080b7-fb15-4300-a52e-623047433cf
f
├─nvme0n1p4 259:4 0 117,6G 0 part /mnt/Backup
└─nvme0n1p5 259:5 0 122,6G 0 part /mnt/Musik
​

sda1 = Debian
sda2 = KDE neon
nvme0n1p2 = Feren OS (mit Grub)

List of /boot folder of Debian:



Addition:
The /efi folder is empty. Same is with /efi folder of second os (KDE neon). Grub bootloader is on MBR (/dev/nvme0n1).

sudo update-grub
[sudo] Passwort für rainer:
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/60_feren-theme.cfg'
Sourcing file `/etc/default/grub.d/90_ferenos.cfg'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found theme: /boot/grub/themes/feren/theme.txt
Found linux image: /boot/vmlinuz-6.8.0-87-generic
Found initrd image: /boot/initrd.img-6.8.0-87-generic
Memtest86+ needs a 16-bit boot, that is not available on EFI, exiting
Warning: os-prober will be executed to detect other bootable partitions.
Its output will be used to detect bootable binaries on them and create new boot entries.
/usr/sbin/grub-probe: Fehler: Unbekanntes Dateisystem.
Found Debian GNU/Linux 13 (trixie) on /dev/sda1
/usr/sbin/grub-probe: Fehler: Unbekanntes Dateisystem.
Found KDE neon User Edition (24.04) on /dev/sda2
Adding boot menu entry for UEFI Firmware Settings ...
done​

/usr/sbin/grub-probe: Fehler: Unbekanntes Dateisystem. >engl: Error: Unknown file system

[oshunluvr]

Found Debian GNU/Linux 13 (trixie) on /dev/sda1

Ok, so grub "sees" it. Now open /boot/grub/grub.cfg with Kate and look for a section that begins with "### BEGIN /etc/grub.d/30_os-prober" or something similar or any section that contains "Debian". Copy and paste that section here.

Then navigate to /mnt/b73f5c2a-b805-4d7c-ba15-36c09afc1e7/boot/ with Dolphin and press F4. This will open a console in that folder. Type this command: ls > ~/files This will place a file named "files" in your home folder. Navigate to your home, open this file with Kate, and paste the contents here.

[Dan-cer]

### BEGIN /etc/grub.d/30_os-prober ###
menuentry 'Debian GNU/Linux 13 (trixie) (on /dev/sda1)' --class debian --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-simple-/dev/sda1' {
insmod part_gpt
linux /boot/vmlinuz-6.12.57+deb13-amd64 root=UUID=b73f5c2a-b805-4d7c-ba15-36c09afc1e77 ro quiet
initrd /boot/initrd.img-6.12.57+deb13-amd64
}
submenu 'Advanced options for Debian GNU/Linux 13 (trixie) (on /dev/sda1)' $menuentry_id_option 'osprober-gnulinux-advanced-/dev/sda1' {
menuentry 'Debian GNU/Linux (on /dev/sda1)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-6.12.57+deb13-amd64--/dev/sda1' {
insmod part_gpt
linux /boot/vmlinuz-6.12.57+deb13-amd64 root=UUID=b73f5c2a-b805-4d7c-ba15-36c09afc1e77 ro quiet
initrd /boot/initrd.img-6.12.57+deb13-amd64
}
menuentry 'Debian GNU/Linux, with Linux 6.12.57+deb13-amd64 (on /dev/sda1)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-6.12.57+deb13-amd64--/dev/sda1' {
insmod part_gpt
linux /boot/vmlinuz-6.12.57+deb13-amd64 root=UUID=b73f5c2a-b805-4d7c-ba15-36c09afc1e77 ro quiet
initrd /boot/initrd.img-6.12.57+deb13-amd64
}
menuentry 'Debian GNU/Linux, with Linux 6.12.57+deb13-amd64 (recovery mode) (on /dev/sda1)' --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-/boot/vmlinuz-6.12.57+deb13-amd64-root=UUID=b73f5c2a-b805-4d7c-ba15-36c09afc1e77 ro single dis_ucode_ldr-/dev/sda1' {
insmod part_gpt
linux /boot/vmlinuz-6.12.57+deb13-amd64 root=UUID=b73f5c2a-b805-4d7c-ba15-36c09afc1e77 ro single dis_ucode_ldr
initrd /boot/initrd.img-6.12.57+deb13-amd64
}
}​

The content of ~/files:

config-6.12.57+deb13-amd64
efi
grub
initrd.img-6.12.57+deb13-amd64
System.map-6.12.57+deb13-amd64
vmlinuz-6.12.57+deb13-amd64

BTW: If I set "debian" instead of "ubuntu" at the top of the UEFI settings, I get Grub from Debian and can start it. The other operating systems are also listed in this Grub.

[oshunluvr]

Well, that all looks normal. It must be an error in the EFI file for Debian, maybe caused by the install-then-reinstall-grub operation. You said your efi folder is empty but it is there on the debian install? Or is there another efi folder somewhere else?

You can either keep trying to fix this, or set Debian to boot and select "ubuntu" to boot to Kubuntu, or make an entry in etc/grub.d/40_custom on Kubuntu for Debian and select it. Something like:

menuentry 'Debian Trixie' --class debian {
insomd part_gpt
insmod btrfs
insmod gzio
search --no-floppy --fs-uuid --set=root b73f5c2a-b805-4d7c-ba15-36c09afc1e77
linux /boot/vmlinuz-6.12.57+deb13-amd64
initrd /boot/initrd.img-6.12.57+deb13-amd64​
}​

To do this, you would have to edit 40_custom every time Debian updated the kernel version.

Most distros will auto-create a set of generic symlinks "vmlinuz" and "initrd.img" that you can use to boot so you won't have to edit 40_custom over and over, but I don't know how to set this in debian. They are normally created automatically when you update the kernel.

Alternately, you can just load the Debian grub menu from Kubuntu with an entry like:

menuentry 'Debian Trixie' --class debian {
insomd part_gpt
insmod btrfs
insmod gzio
search --no-floppy --fs-uuid --set=root b73f5c2a-b805-4d7c-ba15-36c09afc1e77
configfile /boot/grub/grub.cfg
}

[Dan-cer]

Thanks for your engagement.
I could solve the issue now after I stumbled upon a thread about outdated bootmanager of Feren OS. I decided to move Grub/efi to KDE neon (without moving efi partition of course).
And voilà: update-grub output is without errors and includes both other systems.
Now I have - as desired - triple boot with modyfied grub menu.

Issue SOLVED.
Thanks for the very good support here. It was only luck to get the culprit of the issue.