How to Repair, Restore, or Reinstall Grub 2 with a Ubuntu Live CD or USB
When you install windows alongside Linux OS , Grub 2 typically gets overridden. To make Ubuntu/Linux Mint / Kali Linux or any other Linux distro(Linux distribution) control the boot process, you need to reinstall (Repair/Restore) Grub using a live CD or USB
Repair/ Reinstall Grub 2 within a minute:
Mount the partition your Ubuntu/ Mint Kali installation is on. If you are not sure which it is, launch Gparted (included in the live CD / USB) and find out. Replace the XY with the drive letter , and partition number , for example:
sudo mount /dev/sda1 /mnt
sudo mount /dev/sdXY /mnt
sudo mount --bind /dev /mnt/dev && sudo mount --bind /dev/pts /mnt/dev/pts && sudo mount --bind /proc /mnt/proc && sudo mount --bind /sys /mnt/sys
Now we will jump into that using chroot
sudo chroot /mnt
Note: This time you only need to add the drive letter (using a) to replace X , for example: grub-install /dev/sda, grub-install –recheck /dev/sda.
grub-install /dev/sdX grub-install --recheck /dev/sdX update-grub
exit && sudo umount /mnt/sys && sudo umount /mnt/proc && sudo umount /mnt/dev/pts && sudo umount /mnt/dev && sudo umount /mnt
Shut down and turn your computer back on, and you will be met with the default Grub screen.
You may want to update grub or re-install burg however you like it.