Sometimes, especially if you have just installed Windows operating system alongside with your Ubuntu, your precious Grub boot loader will be wiped out from the MBR (Master Boot Record) from your hard disk. How do you restore it?
The steps here have been tested with Ubuntu 9.10.
/. If you have a separate partition for /boot, find it out too. The command sudo fdisk -l may help. Here we assume that the partitions are /dev/sda1 and /dev/sda2 (if any) respectively.sudo mount /dev/sda1 /mnt. If you have a separate partition for /boot, mount it too with sudo mount /dev/sda2 /mnt.sudo grub-install --root-directory=/mnt /dev/sda. (Assume that you want to install Grub to the MBR of /dev/sda.)Reboot your computer and it should work fine now.