Reset Root Password on CentOS 5 & 6

Below are the steps to Reset the Password for Root:

Boot or Reboot your CentOS and Hold the Arrow button to bring the Grub menu, From the GRUB menu, select the appropriate kernel version and press the 'e' key.

You will now be presented with the option menu for the kernel version

From this menu, select the kernel /vmlinuz-... line and press the 'e' key.You will now be presented with the kernel boot options, add single at the end of line, Press enter to save your changes and Press 'b' to boot from this

                                       

This will boot up in single user mode, Now you will boot up to the root shell and you can use passwd to set your new password.

Issue passwd command to reset the password

Reboot and you have a new root password for your CentOS installation.