How to Easily Recover the Root Password in RHEL/CentOS 8: A Step-by-Step Guide

In CentOS 8, like most Linux distributions, the root password is critical for performing administrative tasks. If you've forgotten your root password or need to reset it for any reason, it is possible to recover it with some straightforward steps. Here's a guide on how to recover the root password in CentOS 8.

Prerequisites:

• Physical access to the machine (or virtual machine console).
• The ability to reboot the system and modify boot parameters.

Steps to Recover the Root Password:

Step 1: Reboot into GRUB Menu

Reboot the System:

• Start by rebooting the CentOS 8 system. This can usually be done from the terminal with the reboot command, or by pressing the reset button if you're on a physical machine.

Access the GRUB Menu:

• When the system begins to boot, immediately press the Esc key or Shift key (depending on your system's configuration) to access the GRUB boot loader screen. This is typically displayed briefly at the start of the boot process.

Step 2: Modify GRUB Boot Parameters

Edit GRUB Configuration:

• Once the GRUB menu appears, highlight the boot entry for CentOS (usually the default one) using the arrow keys. Press the e key to edit the boot parameters.

Modify the Boot Command:

• In the GRUB editor, locate the line that starts with linux or linux16 (depending on your system).

At the end of this line, add the following:

rd.break

• This tells the system to break into an emergency shell before mounting the root filesystem.

Boot into Single User Mode:

After adding rd.break, press Ctrl + X to boot with these modified parameters.

Step 3: Reset the Root Password

Access the Emergency Shell:

• The system will boot into a minimal environment with a root shell prompt, typically in a switch_root directory (mounted as /sysroot).

Remount the Root Filesystem:

• The root filesystem is mounted as read-only by default. You need to remount it as read-write to make changes:

mount -o remount,rw /sysroot

Chroot into the System:

• Now, change root (chroot) into the /sysroot directory so that you can interact with your system as if you were in a normal environment:

chroot /sysroot

Reset the Root Password:

• You can now reset the root password using the passwd command:

passwd root

• Enter a new password for the root user when prompted. Make sure the password meets your system’s security requirements.

Relabel SELinux Contexts:

• If SELinux is enabled on your system, it's important to relabel the filesystem after resetting the password to avoid any potential issues:

touch /.autorelabel

Step 4: Reboot the System

Exit and Reboot:

Exit the chroot environment:

exit

Reboot the system:

reboot

• Your system will now reboot normally, and SELinux will automatically relabel the filesystem on startup.

Login with the New Root Password:

• Once the system has rebooted, you should be able to log in with the new root password.

Troubleshooting Tips:

• If you encounter a system that doesn't show the GRUB menu: You may need to press Esc or Shift more quickly, or adjust your bootloader settings in BIOS/UEFI to allow you to see the GRUB menu.
• If the system doesn't boot after modifying boot parameters: Ensure you typed the rd.break correctly and that there are no extra spaces or typos.

Conclusion:

Recovering the root password in CentOS 8 is relatively simple as long as you have physical access to the machine and can modify the boot parameters. By entering single-user mode and resetting the root password through the emergency shell, you can regain control of your system without losing data. Always ensure that your root password is stored securely to prevent future issues.