Installing GRUB from Rescue Mode

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GRUB rescue work is usually needed when the bootloader has been overwritten, the boot menu is missing, or Linux no longer starts after a partition or operating system change.

Boot from rescue media

Start the machine from a Linux live USB or rescue environment. Identify the Linux root partition before running bootloader commands.

lsblk
sudo fdisk -l

Mount the installed system

sudo mount /dev/sdXN /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys

Replace /dev/sdXN with the actual Linux root partition. On UEFI systems, the EFI partition may also need to be mounted under /mnt/boot/efi.

Reinstall GRUB

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

Install GRUB to the disk, not to a numbered partition, unless your distribution documentation says otherwise. Recheck disk names carefully before running bootloader commands.

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