How to Fix the GRUB Error When Booting Linux
Repair the GRUB boot manager when it stops working correctly, step by step.
A broken GRUB is, by far, the most frequent boot problem on Linux — with good news: it almost always has a simple fix, with no data loss.
The most common cause: a Windows update
If you have dual boot with Windows, a major Windows update can overwrite the boot sector, removing the GRUB entry. This does not delete Linux or your data — it only removes the selection menu, letting Windows boot directly.
The simplest fix: boot-repair
- Boot from a Linux Live USB → "Try without installing".
- Open a terminal and install the tool:
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install boot-repair -y
boot-repair
Run the tool and click "Recommended repair" — it automatically detects the problem and fixes it in most cases.
Manual alternative (if boot-repair isn't available)
sudo fdisk -l
Identify your Linux root partition (type "Linux filesystem"), then mount it and reinstall GRUB onto it following your distribution's specific documentation for this step.
Tip: after fixing GRUB, confirm both systems
(Windows and Linux) still show up in the menu — sometimes you need to
run update-grub once more from within Linux for it to
correctly detect both entries.
Frequently asked questions
Does a Windows update delete my installed Linux?
No, it only overwrites the boot selection menu (GRUB), letting Windows boot directly. Linux and your data remain intact on the disk — only the boot menu needs repairing.
Can boot-repair make the problem worse?
It is a widely used and generally safe tool for this specific purpose — the 'Recommended repair' option analyses your configuration before applying any changes.