Reinstalling GRUB

In those times where GRUB is just REALLY broken, you can reinstall it. Set FBR.sh as executable and run it in a terminal. In the menu, Select the option 2: Reinstall GRUB UEFI on a system with UEFI. if you do not have UEFI, select 3: Reinstall GRUB MBR

GRUB MBR

the MBR reinstall option will prompt you to enter the drive GRUB is on. in MOST cases, it should be /dev/sda. to get this, enter this command: sudo mount | grep "/boot "