I have a triple boot system with OpenSolaris, Ubuntu 9.10 and Microsoft Windows XP. I upgraded my Ubuntu 9.10 GRUB to GRUB 2 today. GRUB2 automatically added an entry for Microsoft Windows XP. However, it didn't detect the OpenSolaris that was installed. I had to manually configure OpenSolaris chainloading in GRUB 2. If you are in a similar situation, this will be helpful for you to configure your GRUB 2.

Find your OpenSolaris partition.

$ sudo fdisk -l

Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00099420

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1       12158    97659103+   7  HPFS/NTFS
/dev/sda2   *       12159       24314    97643070   bf  Solaris
/dev/sda3           24317       38913   117250402+   f  W95 Ext'd (LBA)
/dev/sda5           24317       38297   112302351   83  Linux
/dev/sda6           38298       38913     4947988+  82  Linux swap / Solaris

In my case, it is /dev/sda2. Once you have found it, edit /etc/grub.d/40_custom and add the following entry for OpenSolaris. A key difference between GRUB and GRUB 2 is the device numbering. In GRUB, sda2 is (hd0,1). However, in GRUB 2, sda2 is (hd0,2). Keep this in mind when you are configuring your GRUB 2.

# Chainload OpenSolaris GRUB.
menuentry "Chainload OpenSolaris GRUB" {
    set root=(hd0,2)
    chainloader +1
}

Now your /etc/grub.d/40_custom should look like the following.

#!/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.

# Chainload OpenSolaris GRUB.
menuentry "Chainload OpenSolaris GRUB" {
    set root=(hd0,2)
    chainloader +1
}

Then run update-grub to regenerate /boot/grub/grub.cfg.

$ sudo update-grub
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-2.6.31-19-generic
Found initrd image: /boot/initrd.img-2.6.31-19-generic
Found memtest86+ image: /boot/memtest86+.bin
Found Microsoft Windows XP Professional on /dev/sda1
done

You will not find anything about OpenSolaris in the output message. However, you can examine /boot/grub/grub.cfg to find if an entry is added for OpenSolaris.

$ tail -10 /boot/grub/grub.cfg
# 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.

# Chainload OpenSolaris GRUB.
menuentry "Chainload OpenSolaris GRUB" {
    set root=(hd0,2)
    chainloader +1
}
### END /etc/grub.d/40_custom ###