How to repair Boot loader Grub

Boot your computer from a Live USB/CD/DVD

Note: only use a Live USB/CD/DVD of the Ubuntu version that you wish to repair.

However I've used Xubuntu 12.04 to repair 14.04 version

Find a root partition where your Ubuntu is installed

sudo fdisk -l

sudo parted -l

Run the following command into your teminal

sudo mount /dev/sdaX /mnt

Where X is number of partition where your Ubuntu is installed

For example:

sudo mount /dev/sda1 /mnt

This mounts the Ubuntu root partition on the hard drive

Run the following command to install Grub

sudo grub-install /dev/sda --root-directory=/mnt

Done

Reboot your machine

sudo reboot

You should see now grub menu now with your installation, so just login your Ubuntu now and run the following:

sudo update-grub

It will update your grub if you have other OS installed

sudo reboot

Done!… Read the rest