Recover or Reinstall the GRUB Bootloader

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GRUB recovery is needed when a system no longer reaches the boot menu or when another operating system has overwritten the bootloader. The safest approach is to boot from live media, identify the installed Linux system, then reinstall GRUB carefully.

Identify disks and partitions

lsblk
sudo fdisk -l

Confirm the root partition and the boot mode, especially on UEFI systems where an EFI System Partition is involved.

Mount and chroot

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

Reinstall and rebuild the menu

grub-install /dev/sdX
update-grub

Use the disk name for grub-install, not a numbered partition, unless your distribution has different instructions. Reboot only after checking for errors.

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