Ubuntu 15.10 GRUB boot menu

How to password-protect GRUB

Password-protecting the bootloader is one method you may employ to enhance the physical security profile of your computer. GRUB, the GRand Unified Bootloader, is the default bootloader on virtually all Linux distributions, but on a significant number, the installer does not have support for setting a GRUB password. This article presents the step involved in password-enabling GRUB - on a running system. Before we go through the steps involved in setting a password for GRUB, it's best to understand why this is even necessary. Principally, we password-enable GRUB to:
  1. Prevent Access To Single User Mode — If an attacker can boot into single user mode, he becomes the root user.
  2. Prevent Access To the GRUB Console — If the machine uses GRUB as its boot loader, an attacker can use the edit the command’s interface to change its configuration or to gather information using the cat command.
...