How to Repair Grub on Ubuntu / Linux Mint

1. Boot from Your Ubuntu/Linux Mint Live DVD/CD/USB


2. Open Terminal


3. Check Your partition list, use :
sudo fdisk -l


4. Mount your root partition at /media, assuming is /dev/sda3
sudo mount /dev/sda3 /media


5. then, re-install Grub
sudo grub-install --root-directory=/media /dev/sda


6. Reboot Your machine, then eject you Live DVD/CD/USB


7. After you successfully to log-on to Ubuntu/Linux Mint desktop, let's open your Terminal again, then update Grub
sudo update-grub


8. Reboot :D and Your Grub will successfully repaired!