grub rescue unknown filesystem 🐧 Linux

error: unknown filesystem. Entering rescue mode... grub rescue>

GRUB can’t find or read the partition holding its files — common after resizing/deleting partitions or installing Windows alongside Linux.

Seen on: Linux

Meaning

GRUB’s core image remembers where /boot/grub lives. Moving, resizing or deleting that partition (or Windows overwriting the boot loader) leaves it pointing nowhere.

Common causes

  • Partition containing /boot deleted, moved or resized
  • Windows installation/update changed the boot setup
  • Disk order changed (new disk added)

⚡ Quick fix

  1. From grub rescue: find the partition with ls, set prefix/root, insmod normal, normal
  2. Then reinstall GRUB from Linux
  3. Or boot a live USB and reinstall GRUB (boot-repair)

Detailed fix by platform

GRUB

  1. bash
    grub rescue> ls
grub rescue> ls (hd0,gpt2)/boot/grub
grub rescue> set root=(hd0,gpt2)
grub rescue> set prefix=(hd0,gpt2)/boot/grub
grub rescue> insmod normal
grub rescue> normal

Ubuntu

  1. sudo grub-install /dev/sda && sudo update-grub # after booting into the system

How to diagnose

  1. Partitions — ls in grub rescue
  2. Change — Recent partitioning/Windows install?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

🧠 Still stuck? Analyze your error

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