Quick guide to recover a corrupt GRUB bootloader in Linux

✨ Quick Answer

GRUB bootloader failure (leaving the system frozen at the grub> rescue console) usually occurs after a failed kernel update, EFI partition table failures, or after configuring dual boots with Windows. To repair it, we must mount and enter the damaged file system from a temporary environment.

Quick Diagnostics

Cause

GRUB bootloader removed or corrupted after Windows Update

Solution

Boot from Live USB and reinstall GRUB: grub-install /dev/sdX

Cause

Corrupted or outdated /boot/grub/grub.cfg file

Solution

Regenerate boot config: grub-mkconfig -o /boot/grub/grub.cfg

GRUB bootloader failure (leaving the system frozen at the grub> rescue console) usually occurs after a failed kernel update, EFI partition table failures, or after configuring dual boots with Windows. To repair it, we must mount and enter the damaged file system from a temporary environment.

Step-by-Step Solution

1. 1

   Step 1: Iniciar desde una distribución Live USB y localizar particiones

   Insert a Live USB compatible with your current distribution, boot it in UEFI/BIOS mode, and detect your hard drive identifier:

   BASH Copy

   sudo fdisk -l
   

   (Identify your Linux root partition, for example /dev/sda2, and the EFI partition in FAT32 format, for example /dev/sda1).

2. 2

   Step 2: Montar el sistema dañado y preparar el chroot

   Mount the directory structure of the damaged file system in the temporary session:

   BASH Copy

   # Montar partición raíz
   sudo mount /dev/sda2 /mnt
   
   # Montar directorios de comunicación del kernel
   for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
   
   # Montar partición EFI si usas UEFI
   sudo mount /dev/sda1 /mnt/boot/efi
   

3. 3

   Step 3: Entrar al sistema (chroot) y reinstalar GRUB

   Log in as a superuser into your original file system environment and reinstall the bootloader:

   BASH Copy

   # Cambiar la raíz del shell
   sudo chroot /mnt /bin/bash
   
   # Reinstalar GRUB apuntando al disco (reemplazar /dev/sda por el disco físico general)
   grub-install /dev/sda
   
   # Regenerar el archivo de configuración del menú de arranque
   update-grub
   
   # Salir y desmontar
   exit
   sudo reboot