Restore or Reinstall Ubuntu grub after reinstalling Windows

If we reinstall windows on a Windows/Ubuntu dual boot system, we can not use Linux, until the Grub (GRand Universal Bootloader) is restored.

To restore grub, Insert the live CD/DVD of Ubuntu and restart the system to start a live session.




For Ubuntu versions 9.10 and above:

Then open a terminal from Applications --> Accessories --> Terminal and enter the following command.

Code:

sudo fdisk -l

You will see something like this:




Select the drive in which root partition "/" is installed.. (Let us say /dev/sda5)

Then in terminal

still in the terminal, type:

Code:

sudo mkdir /media/sda5
sudo mount /dev/sda5 /media/sda5

And then, to reinstall the grub by entering:

Code:

sudo grub-install --root-directory=/media/sda5 /dev/sda

Of course you need to replace “/dev/sda5″ and “/dev/sda” with what you found in the fdisk output.


If you get BIOS warnings try:

sudo grub-install --root-directory=/media/sda5 /dev/sda --recheck

If everything is fine type in the following into terminal:

Code:

sudo reboot

For Ubuntu versions 9.04 and lower:

We need to open terminal from

Applications --> Accessories --> Terminal and enter the command.

Code:

sudo grub

Next,

Code:

find /boot/grub/stage1

Take note of what it returns (something like (hd0,1).)

Now enter

Code:

root (hda,b)

Replace a and b with what you got back before. For example, if "find /boot/grub/stage1" gives "(hd0,3)", you will run "root (hd0,3)"

Now run:

Code:

setup (hd0)

This is fine if you want to write GRUB to the MBR. If you want to write it to your Linux root partition, then you want the number after the comma, such as "(hd0,3)".



If everything is fine type in the following into terminal:

Code:

sudo reboot

Enjoy...



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