I’ve got a triple boot system with OS 12.1, Ubuntu 11.10, and Win XP.
The last round of system updates overwrote my boot menu and I have lost access to my Ubuntu partition. The current set up shows only the OpenSuse and Windows options, and both of those work, so I just need to add Ubuntu to the OpenSuse boot menu. (This might be easier since the Suse boot menu is in use after the update.) I am not sure exactly how to go about this, so thought I’d ask first – before I foul something up.
The main partitions are as follows:
/dev/sda2 = Windows XP
/dev/sdb1 = Ubuntu 11.10
/dev/sdc2 = OpenSuse 12.1
So the general rule would be to install Windows, then openSUSE and then Ubuntu. If you break the Grub 2 boot up, here is a link you could use to fix the problem: How to Restore Grub 2 As The Main Bootloader
May I also say that loading openSUSE 12.1 as your main, then VirtualBox and loading Windows and Ubuntu into VirtualBox is the best way to go. Bump up your base memory (which has never been so cheap) and perhaps disk space (though it sounds like you have enough there already) and never have your boot loader messed up again. Its what I use these days.
Followed the directions in the Grub 2 article you posted and got an error. It said something about it couldn’t do block lists and refused to work. I can still boot into OpenSuse or XP, which is a good thing. I was using the Ubuntu Grub before, since that was the last thing that was installed.
You should install Grub2 in MBR, so it uses the filesystem to find its core and not block lists (offset position of sectors on disk). The error you got is normal if you tried to install the Grub2 bootloader in a partition bootsector. You can do it though with the --force option, but it’s not as good and might stop working after a brutal fsck. Install Grub2 in /dev/sdb and make sure that this drive has boot priority, and you will boot into Ubuntu’s Grub2. Don’t mess up with kernel device names (sda, sdb, etc)! Never use them anywhere in /etc/fstab or boot menu.