How do I restore multiboot function on WinXP/Ubuntu Hard drive?

Question

I have a multiboot WinXP/Ubuntu Hard Drive but something has gone wrong and multiboot stopped working. So, my access to Ubuntu installation is lost on the HDD. How do I restore the multiboot function to return to Ubuntu? Thanks a lot

Answer 1

You have probably overwritten your bootsector. Try to use the Supergrubdisk. If that for some reason does not work, you can try the guide from the german ubuntu users wiki:

http://wiki.ubuntuusers.de/GRUB#Methode-2-root-directory-Variante

Start from a Ubuntu installation CD (or any other linux that runs from CD like knoppix). Then mount your Ubuntu root partition from the HDD to some folder, for instance /mnt. If you have a separate /usr, /boot or /etc partition, please mount it in the corresponding subfolder of the root parition (so if root is mounted at /mnt, then boot should be at /mnt/boot and so on). When finished, you can simply "sudo grub-install --root-directory=/mnt /dev/sda" (of course only if your hdd is sda).

If the last step doesn't work, because your installation is too outdated, you should still be able to use the chroot-method also given at ubuntuusers.de: Mount the root and boot partition as written above and bind the /dev directory so that you also have it available within the mounted root partition (assuming the root partition is mounted at /mnt):

sudo mount -o bind /dev /mnt/dev 

Same for /sys and /proc

sudo mount -o bind /sys /mnt/sys 
sudo mount -t proc /proc /mnt/proc 

Now you can chroot

sudo chroot /mnt /bin/bash 

And you should be ready to run "grub-install /dev/sda". It's also a good idea to run "update-grub" afterwards.