How to Reset Root Password in Linux

This article will help to reset the root password if you have forgotten of your Linux machine.

This steps will adding a “rd.break” to the end of the line with kernel parameters in Grub to stops the start up process before the regular root filesystem is mounted, hence the necessity to chroot into sysroot.

This will allow you to break into your linux system and reset root password back to your own.

Reset Root Password on Linux

Follow the below steps to reset forgotten root password on your Linux machine.

1. First of all, reboot your system and interrupt the countdown in the boot loader menu.

To interrupt the countdown, you need to press any key when the boot loader menu appears.

2. Now edit the default boot loader entry to abort the boot process just after all file systems have been mounted, but before control in handed over to systemd, then boot.

Use the cursor keys to highlight the default boot loader entry. On the GRUB 2 boot screen, press e to edit the current entry.

3. Using the cursor keys, navigate to the line that starts with linux16 if you are using on x86-64 BIOS-based systems and navigate to the line that starts with linux line on 64-Bit IBM Power Series.

Press End to move the cursor to the end of the line.

4. Next append “rd.break” or “rd.break enforcing=0” to the end of the line. Both gives the same result.

# rd.break

OR

# rd.break enforcing=0”

Use option “rd.break”.

Next use option “rd.break enforcing=0”.

5. Now press the Ctrl+X to boot using the modified configuration.

6. The file system is mounted read-only on /sysroot/. You will not be allowed to change the password if the file system is not writable. Run the following command to remount the root filesystem in read-write mode.

# mount -oremount,rw /sysroot

7. After that use chroot to go into a chroot jail at /sysroot. Change the file system’s root as follows.

# chroot /sysroot

8. Now change root password to your own password.

# passwd root

9. Configure the system to automatically perform a full SELinux relabel after boot. This is necessary since the passwd tool re-created the /etc/shadow file without an SELinux context.

10. Type exit twice to continue booting your system as normal. The system will run an SELinux relabel, then reboot again by itself.

Resource: https://www.ehowstuff.com/reset-forgotten-root-password-on-linux/