How-to boot FreeBSD with Grub2 under Ubuntu 10.10

12-10-2010 · author: rick · ubuntu, freebsd,gpt

I recently upgrade to Ubuntu 10.10. Which also caused grub to be updated to version 1.98 (to be exactly {1.98+201000804-5ubuntu3), which used a different syntax to define partitions instead of numbers which where off by one, they now use msdosX style formatting.

My FreeBSD is located at /dev/sda3 on a good old MBR partition table and I want to use the good old FreeBSD boot loader as well (so chainloading is required). To activate within Ubuntu. Put the following contents in file:/etc/grub.d/40_custom:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry "FreeBSD (on /dev/sda3)" {
	savedefault
        insmod chain
	set root='(hd0,msdos3)'
	chainloader +1
}

Note

My hd0 is file:/dev/sda under Linux and got named file:/dev/ad6 under FreeBSD If you want to boot of a GPT partion use the following syntax

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry "FreeBSD (on /dev/ad6p3)" {
	savedefault
        insmod ufs2
	set root='(hd0,gpt3)'
	kfreebsd /boot/loader
}

Update your grub and use should be done: rick-eee$ sudo update-grub

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