Linux GRUB Error — Boot Loader Failed Fix

What Does This Error Mean?

GRUB is the bootloader that loads Linux when you turn on your computer. When GRUB has an error, you see a black screen with a 'grub>' or 'grub rescue>' prompt, or error messages like 'error: no such partition' or 'file not found.' This usually happens after a disk change, a failed system update, or Windows overwriting GRUB.

Affected Models

Ubuntu
Debian
Fedora
Arch Linux
Linux Mint
openSUSE

Common Causes

Windows was installed after Linux and overwrote GRUB with the Windows bootloader
The disk partition layout changed — a partition was resized, deleted, or renumbered
A kernel update failed and GRUB cannot find the new kernel files
The GRUB configuration file became corrupted during an update
The EFI partition was accidentally formatted or had its contents deleted

How to Fix It

Boot from a Linux live USB. Create a bootable USB drive with the same Linux distribution you have installed. Boot from it to get a working Linux environment.

You can create a live USB using tools like Rufus (Windows) or the Startup Disk Creator (Ubuntu). Most distributions provide ISO download links on their website.
Find your Linux partition. From the live USB, open a terminal and run: sudo fdisk -l or lsblk to see your partitions. Identify your root partition (usually ext4 and the largest one).

Note the device name of your root partition — for example, /dev/sda2 or /dev/nvme0n1p2.
Use Boot-Repair tool (Ubuntu/Ubuntu-based). Install and run: sudo apt install boot-repair then: boot-repair. Click Recommended Repair and follow the instructions.

Boot-Repair automates the entire GRUB reinstallation process. It is the easiest approach for Ubuntu and Linux Mint users.
Manually reinstall GRUB. Mount your root partition: sudo mount /dev/sda2 /mnt (replace sda2 with your partition). Then: sudo grub-install --root-directory=/mnt /dev/sda and: sudo update-grub

For UEFI systems, you also need to mount the EFI partition and use --target=x86_64-efi. The Boot-Repair tool handles this automatically.
Restore GRUB from a chroot. Mount your system, chroot into it, and reinstall GRUB: sudo mount /dev/sda2 /mnt && sudo chroot /mnt && grub-install /dev/sda && update-grub && exit

Chroot makes your terminal think it is running inside your installed Linux system. This is the most thorough method for GRUB repair.

When to Call a Professional

GRUB repair requires booting from a live USB and some comfort with terminal commands. If you are not comfortable with this, any Linux-knowledgeable friend or technician can fix a GRUB error in under 30 minutes. Your data is almost certainly safe — GRUB is separate from your personal files.

Frequently Asked Questions

Will fixing GRUB delete my files?

No — GRUB is stored in a separate area of the disk, not in your personal files. Reinstalling GRUB does not touch your home folder, documents, or any installed programs. Your files are safe even if GRUB is completely broken.

Windows deleted my GRUB after a Windows update. How do I restore it?

Windows updates often reinstall the Windows bootloader, overwriting GRUB. Boot from a Linux live USB and reinstall GRUB using the steps above. Consider installing and enabling os-prober so GRUB includes Windows in the boot menu.

What is the difference between GRUB and GRUB rescue?

The normal GRUB menu lets you choose between operating systems. The 'grub>' minimal shell appears when GRUB loaded successfully but cannot find the config file. The 'grub rescue>' emergency shell appears when GRUB has a more serious problem finding its own files. Both can be fixed by reinstalling GRUB from a live USB.