Restoring the Grub after reinstalling Windows

After reinstalling windows or fixing MBR(Master Boot Record) you always loose your grub and you cannot boot to your linux. So this post is about the methods of restoring the grub. There are three methods I use. I will explain all three.

All three methods need a live cd of a linux. You need to boot from the live cd and take the terminal and do the following:

1. First method is using grub command. We initially go into the grub mode interface using the command
   sudo grub

   This will get you a “grub>” prompt (i.e. the grub shell). At grub>. enter these commands

   find /boot/grub/stage1

   If the find returned (hd0,1) then you would enter

   root (hd0,1)

   Now the root drive where the boot folder is mounted.Now we needed to setup the drive to boot to show the grub. We do this by

   setup (hd0)

   Finally exit the grub shell

   quit

   And then Reboot to and try if you are getting the grub.
   If not try the next method.

2. If couldn’t get grub to find the stage1 file or even recognize the drive. Use this method.
   sudo mkdir /mnt/root 

   sudo mount -t ext3 /dev/sda6 /mnt/root

   Then you have to mount the proc subsystem and udev inside /mnt/root also:

   sudo mount -t proc none /mnt/root/proc 

   sudo mount -o bind /dev /mnt/root/dev

   Doing this allows grub to discover your drives. Next you have to chroot:

   sudo chroot /mnt/root /bin/bash

   Now that you’re chrooted into your drive as root everything should work.

   sudo grub

   And then follow the 1st method to install the grub.

3. In lastest Linux you can use the command grub-install.The usage of this command is as
   sudo grub-install –root-directory=/media/<root-drive-mount> /dev/sda

   It might be hda if the hard disk is IDE and sda if disk is SATA.

So try it out the next time you loose your grub and tell me how it went.

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