Reset the root password: Debian

The root password can be reset using the GRUB (Grand Unified Bootloader) menu to boot the system into single-user mode or with a recovery shell.

Prerequisites

• Physical access to the server/machine console.
• The Debian operating system must be using GRUB as the bootloader.

Step-by-Step to Reset the Password

1. Access the GRUB Menu

1. Reboot your Debian system.
2. Wait for the GRUB menu to appear on the screen;
3. Use the arrow keys (↑ and ↓) to select the Debian kernel entry (usually the first option).

2. Edit the Boot Parameters

1. Press the e key to edit the boot commands of the selected entry.

2. Use the down arrows to locate the line that begins with linux (or linuxefi). This line contains the kernel path and its boot parameters.

3. On that line, locate and replace the ro (read-only) parameter with rw (read-write).

4. At the end of that same line, add the following parameter to load the bash shell as the main init process:

   init=/bin/bash
   Example of how the modified line will look:

   linux /boot/vmlinuz-5.10.0-23-amd64 root=UUID=... rw quiet init=/bin/bash

3. Boot the System and Change the Password

1. Press Ctrl+X to boot the system with the new parameters.

2. The system will skip the normal init process and directly load a shell as the root user (indicated by #).

3. Run the passwd command to reset the root user’s password:

   passwd

4. Type the new password and confirm it when prompted. Characters will not be displayed (standard security behavior).

5. A message like password updated successfully will confirm the change.

4. Reboot the System

1. Reboot the system after changing the password. Use the exec command to return to the normal init process:

   exec /sbin/init 6

2. Debian will reboot. At the login prompt, you can use the username root and the new password you just set.