How To Reconfigure GRUB from LiveUSB

By Lye Heng Foo on May 2, 2025

On a dual boot computer, a corrupted GRUB may happen after performing a major Windows update. In order to fix the broken GRUB, please boot using a Ubuntu LiveUSB (or LiveCD).

After the computer is booted in Ubuntu, open a Terminal window, and type the following commands to re-install GRUB.

Re-installing GRUB

# Example (for the case Linux is installed at /dev/sda5):
# Otherwise, change all /dev/sda5 to your /dev/sda<#> or /dev/sdb<#>
# NOTE: If not sure which partition has Linux been installed on,
# you may run 'fdisk -l' to view partition information first.

sudo mount /dev/sda5 /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /sys /mnt/sys
sudo mount --bind /proc /mnt/proc
sudo mount /dev/sdaX /mnt/boot   #only if /boot is mounted as separate partition at /dev/sdaX

sudo chroot /mnt
sudo update-grub
sudo grub-install /dev/sda
exit

sudo umount /mnt/dev
sudo umount /mnt/sys
sudo umount /mnt/proc
sudo umount /mnt/boot   #Only if you mounted it earlier
sudo umount /mnt/
sudo reboot

Hope this solution helps you.

If it doesn’t, you may also try an alternative fix (suggested by others):

Alternative Fix

sudo mount /dev/sda5 /mnt
sudo grub-install --root-directory=/mnt /dev/sda
sudo umount /dev/sda5
sudo reboot

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