Resetting forgotten root password on CentOS

Boot the system and when you see the following screen, press any key

At the following screen, press e

It will take you the following screen

Highlight the line with vmlinuz in it by using the arrow keys and press e. The next screen will look like below

Now type single or init 1 at the very end of the line so.

Then press enter and b to boot the system with the new argument
The system will boot into single user mode and you will see bash prompt like below

Now change the password

 passwd
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

type in the new password and then reboot

reboot

to restart the system.