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!

How to Repair Grub on Fedora

1. Boot Your Fedora Live DVD/CD/USB

2. Open terminal

3. Check the 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 grub2-install --root-directory=/media /dev/sda

6. Update grub

sudo grub2-mkconfig -o /media/grub2/grub.cfg

7. You will have to adjust for your actual layout.