In my office, we must use the ugly M$ Windows. So after many year of single GNU/Linux booting, I need to install Windows again as a dual boot.

But with Micro$oft, nothing is easy, even an install… After the installation, the Windows bootloader erase the GNU/Linux boot. To fix that, we need a live CD of a GNU/Linux distribution.

  • After the boot in the live CD, just mount the partition /boot in a folder (in this example /mnt) with the command sudo mount /dev/sdXY /mnt (where X is the drive letter and Y the partition).
  • Chroot into the mounted folder with the command sudo chroot /mnt.
  • Reinstall GNU/GRUB with sudo grub-install --root-directory=/mnt /dev/sdX.
  • Update the boot menu with sudo update-grub.
  • Reboot and enjoy !