Trying to get Grub2 to see my Gentoo kernel

[davidogg]

I have several Linux distro's spread out on these 2 drives. sdb is the primary slave, sda is the secondary master. (they got jumpered goofy years ago, and I havent dared touch it, but it seems to work, so...)

I installed Gentoo on sda7, and when I run update-grub from Ubuntu, it sees my gentoo kernel and appears as though it's added it, however when I reboot it doesn't show in the menu. Grub is on sdb1, I believe

This is my rats nest of partitions;

david@david-lucid:~$ sudo fdisk -l
[sudo] password for david:

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x90c090c0

Device Boot Start End Blocks Id System
/dev/sda1 3826 60801 457659658 f W95 Ext'd (LBA)
/dev/sda2 1 3825 30724281 7 HPFS/NTFS
/dev/sda5 31744 60801 233408385 7 HPFS/NTFS
/dev/sda6 3826 7678 30949159+ 83 Linux
/dev/sda7 7679 11047 27061461 83 Linux
/dev/sda8 11048 14234 25599546 83 Linux
/dev/sda9 14235 14549 2530206 82 Linux swap / Solaris
/dev/sda10 14550 31743 138110773+ 83 Linux

Partition table entries are not in disk order

Disk /dev/sdb: 160.0 GB, 160029999616 bytes
255 heads, 63 sectors/track, 19455 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xab42ab42

Device Boot Start End Blocks Id System
/dev/sdb1 * 1 13 102400 7 HPFS/NTFS
Partition 1 does not end on cylinder boundary.
/dev/sdb2 13 5074 40653481 7 HPFS/NTFS
/dev/sdb3 5075 18822 110430810 83 Linux
/dev/sdb4 18823 19455 5084572+ 82 Linux swap / Solaris

Disk /dev/sdc: 4022 MB, 4022337024 bytes
124 heads, 62 sectors/track, 1021 cylinders
Units = cylinders of 7688 * 512 = 3936256 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000a9d0a

Device Boot Start End Blocks Id System
/dev/sdc1 * 1 1021 3924693 c W95 FAT32 (LBA)
david@david-lucid:~$

This is the output from update-grub;

david@david-lucid:~$ sudo update-grub
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-2.6.32-23-generic
Found initrd image: /boot/initrd.img-2.6.32-23-generic
Found linux image: /boot/vmlinuz-2.6.32-22-generic
Found initrd image: /boot/initrd.img-2.6.32-22-generic
Found linux image: /boot/vmlinuz-2.6.32-21-generic
Found initrd image: /boot/initrd.img-2.6.32-21-generic
Found memtest86+ image: /boot/memtest86+.bin
Found Gentoo Base System release 1.12.13 on /dev/sda7
Found Windows 7 (loader) on /dev/sdb1
Found Ubuntu maverick (development branch) (10.10) on /dev/sdb3
done
david@david-lucid:~$

Am I doing it wrong?

[lechien73]

I had read about this before, where os-prober (or linux-boot-prober - depending on which one you're using) detects another operating system, but then fails to add it to Grub.

Others have said that os-prober seems to be better than linux-boot-prober at detecting other operating systems. So you could check which prober you're using:


which os-prober
which linux-boot-prober


If os-prober doesn't return a path (/usr/bin/os-prober), then you can install and use it by typing:


sudo apt-get install libdebian-installer4
sudo os-prober
sudo update-grub


If things are still the same when you reboot, then another solution would be to include the Gentoo installation in the /etc/grub.d/40_custom file. You can do this by adding the following lines after the comment:


echo "Adding Gentoo Base System" >&2
cat << EOF
menuentry "Gentoo Base System custom" {
set root=(hd0,7)
linux /boot/gentoo root=/dev/sda7 ro
}
EOF

Then make the file executable:


sudo chmod +x /etc/grub.d/40_custom

Finally:


sudo update-grub

And reboot one more time :)

[ogredeschnique]

I'm receiving a "file missing" error after adding my Gentoo info /etc/grub.d/40_custom.
I guess it's time to get familiar with the grub2 command line at boot.

Seems like this should work properly.


menuentry "Gentoo Linux" {
set root=(hd0,2)
linux /boot/gentoo-2.6.34-r1 root="/dev/sda3"
}
EOF

[Another edit]
Ah ha. I just noticed that grub2 numbers devices differently. The first disk is still zero, but the third partition is not the third from zero. That is so weird.