os-prober should chainload other linux if there is bootloader on the partition

[Andrew Jorgensen]

Binary package hint: os-prober

I have two Linux distributions installed. SUSE prefers to install it's bootloader on it's root partition rather than on the MBR. Ideally os-prober / grub-common would see that the partition has a bootloader (grub) on it and chainload instead of loading the other distro's kernel directly.

This approach would be a lot safer than the current approach because it would allow the other distro to fully control the kernel parameters used to boot and would (assuming the distro takes care of this itself) allow the other distro to upgrade it's kernel or change parameters without os-prober needing to re-detect.

[David (deivi73)]

I solved this issue with two modifications.

In first place, I wrote a grub detector based on /usr/lib/os-probes/mounted/90linux-distro with sequence number 89 to run before linux distribution detection:

/usr/lib/os-probes/mounted/89grub is attached

Then, I modified /etc/grub.d/30_os-prober to deal with the grub case. I set the following before the *) default option:

grub)
      found_other_os=1
      cat << EOF
menuentry "${LONGNAME} (on ${DEVICE})" --class linux --class gnu --class os {
EOF
      GDRIVE="`grub-probe -d /dev/sda4 -t drive 2> /dev/null`"
      cat <<EOF
 insmod ext2
 set root='${GDRIVE}'
 chainloader +1
}
EOF
    ;;
*)

[David (deivi73)]

I forgot to attach the file that should be installed in /usr/lib/os-probes/mounted/89grub

It returns "grub" as detected OS and it is parsed later in /etc/grub.d/30_os-prober

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.