HowTo: Restore grub2 after Windows installation

I am planning to publish my latest adventures with audio processing on Linux. Stil, in the meantime I would like to share a quick guide to restore the grub2 boot system after you install any Windows OS with EFI support on the same machine (AKA dual boot).


Assuming you only have Windows at your disposal and no rescue Linux pen drive, you can proceed this way:

  1. On Windows, open a new terminal with Administrative access
  2. On the terminal run bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi (change ubuntu for your Linux distro’s name)
  3. Restart your machine. If everything worked correctly, you will see the grub2 back
  4. On the grub2 menu, select your Linux distribution
  5. On your Linux distribution, open a new terminal
  6. On the terminal run sudo update-grub2

Now you’re good to go, but if you want to understand what happened underneath, I invite you to continue reading.

The nitty-gritty details

bcdedit is a command-line tool for managing “Boot Configuration Data (BCD)”. So, the command you run on Windows changed the file path for the EFI boot configuration, in this case, we are setting the grub2 configuration file instead of the Windows' one.

Changing the EFI boot configuration will solve half of the problem since you still need to update grub2 to recognize the other EFI-compatible OS on the machine (Windows). You could have done this manually by editing the grub2 configuration files, but you would be asking for trouble there. Instead, you can simply run the update-grub2 command, which will scan the EFI partition and update all the files accordingly.

And that’s it, you are good to hack around once again!

Last modified on 2021-10-04