Decided to stop trying to setup dual booting with os-prober and went for chainloader instead

English Install/Boot/Login
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Hello. A little bit unusual, but this one is an answer, not a question.

I just installed opensuse tumbleweed in my PC again after a while, but, since the main system is Debian, I decided to ditch opensuse’s own bootloader and went through the os-prober-from-Debian route instead. Except that now, instead of switching to ext4 as before, I decided to leave btrfs as the default (which means the installer creates a multi-volume btrfs partition).

os-prober successfully detected opensuse and added an entry to Debian’s grub.

It didn’t boot. Something related to not finding the default snapshot that Debian didn’t know about, I think.

After failing to find any answers regarding how to solve this problem in Debian’s grub installation, I decided to bypass it and just go directly to opensuse’ grub, no questions asked:

# /etc/grub.d/40_custom
menuentry 'openSUSE (chainloader)' --class opensuse --class gnu-linux --class gnu --class os {
    insmod chain     # enable chainloader
    insmod btrfs     # enable btrfs
    insmod part_gpt  # enable gpt partitions (must come after `insmod btrfs`)
    set root=(hd2,gpt1)
    chainloader +1
}

(To find the root, I recommend opening a command prompt from grub and ls-ing the partitions to find the one you want)

Not only this solved the multivolume btrfs issue, but this also means I don’t need to worry about updating grub from inside Debian everytime I upgrade opensuse’s kernel like I had to before. I leave it to opensuse to decide how to best setup its own boot.

Considering I was also planning on installing other operating systems alongside Debian and opensuse, this solution is very reassuring and honestly I think it should be the default instead of having a foreign operating system try and figure out how to boot the system.

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Some other multiboot alternatives are discussed @How to have a custom UEFI grub menu for a multiboot system.

1 Like
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It is not needed for legacy chainloading.

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I couldn’t find the partitions of the disk where opensuse was installed without that

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I have no idea what you mean. There is no search statement in this menu entry. The partition is hardcoded.

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While on the GRUB console, the partitions of (hd2) simply wouldn’t appear (e.g. via ls) if I didn’t insmod btrfs then insmod part_gpt. Setting the root to (hd2,gpt1) would not would if I didn’t do that.