Ubuntu Bootloader Guide

Recover/Reinstall/Repair grub2 from Linux Live CD/USB

Boot your Linux Live CD/USB then open Terminal and enter following commands:

sudo -i

Check the drives number in Partition Manager :

sudo fdisk -l

Now select your Linux installed drive and change the number in following commands (Only change 'x' with your drive number) and change (sda) with your hard drive it can be (sdb, sdc, etc) you can see this in Partition Manager:

sudo mount /dev/sdaX /mnt
sudo mount /dev/sdaX /mnt/boot
sudo mount --bind /dev /mnt/dev/

This command will change mnt directory permissions to root permissions:

sudo chroot /mnt

Now grub install command and Change 'a' in "sda" with your hard drive where you want to install grub, check in Partition Manager:

grub-install /dev/sda

Unmount

sudo umount /mnt/dev
sudo umount /mnt

Restart

sudo reboot