How to break root password centos 6

As your system starts to boot, you will need to press the "Escape" key to access the GRUB menu screen:

 

From this initial menu, highlight your operating system using the arrow keys. At this screen you are presented with various options. Now press "e" to edit.

 

Now highlight the line starting "kernel" and press "e" again to edit the highlighted parameter.

Once you press "e" you will be taken to the end of the line. Here you will need to press the "space" key and then add the number "1" to the end of the line as per image below.

 

Now press "Enter" to accept your entry. You will be taken back to the previous screen.

 

Now press "b" to boot your system.

Your system should now boot into "Single User Mode"

 

At the command prompt you can issue the command "passwd" to change the root account password.

 

Now reboot your system by issuing the "reboot" command.

Your system will now reboot normally back to its normal runlevel.