One of my students had a laptop with a windows partition and an Ubuntu install side by side. Something (unknown to me) made her GRUB install bail, so she took it to IS and got her MBR put back in place, which of course made her Linux install invisible.
Rather than actually re-install Ubuntu (which was pretty new actually, it wouldn’t have been terrible), I asked if I could try recovering it. We made it work, and here’s how:
- Boot your computer up with the Ubunto CD and begin a normal installation.
- Go through each step until you come to the partitioning section.
- Choose Manual Partition.
- Find your main Linux partition and set it to use whatever filesystem it’s supposed to have (ext3 for example), and the mount point (/ for example).
- DO NOT FORMAT THEM. (formatting swap is ok if it makes you)
- Finish the manual partition
- Say "Yes" when it asks you to save the changes.
- It will give you errors saying that "the system couldn’t install ….." after that. They’re big and red and scary, but don’t worry about it.
- Ignore them, keep select "continue" until you get back to the Ubuntu installation menu.
- Down several options you’ll see Install Grub…
- You may see several more big red scary screens, but again, don’t worry about it..
- Once the GRUB install is finished, reboot, taking out the cd before you get to the part where it would boot from cd.
You should be good to go.
I just put together short instructions how to do this on any distro using Knoppix. Right here: http://dev.ciho.net/posts/repairing-grub/
Should help the non-Ubuntu users.