Warning: this guide is only a personal note to remind myself when I have to restore Grub again.
In my previous post, I had just installed Windows 7 as a dual boot with Debian on my Toshiba laptop. The following describe the steps taken to restore the Grub boot loader so that Debian can be started again.
I booted the laptop with Ubuntu Live CD, then open a Terminal. To get the partition tables, as a root execute the fdisk command:
# fdisk -l
In my case, / and /boot reside in /dev/sda6. Once the device has been identified, I need mount it using mount command:
# mkdir /mydisk
# mount /dev/sda6 /mydisk
Next use chroot command to start interactive shell with special root directory.
# chroot /mydisk
Now, we can reinstall grub with grub-install command:
# grub-install /dev/sda
In my case, I have a SATA drive, so the device is sda. If you have an IDE drive, it should be /dev/hda.
Reboot the system. I saw the Grub menu again, and I can boot to either Windows 7 or Debiain.
Credit: Restore Debain Linux boot loader