Reset forgotten root password with Centos 5/6
Please Note: In order to reset your Centos 5/6 password you will need KVM access to adjust your servers boot loader menu!
1.) At the boot loader menu, use the arrow keys to highlight the installation you want to edit and type [A] to enter into append mode.
2.) You are presented with a prompt that looks similar to the following:
grub append> ro root=LABEL=/
3.) Press the Spacebar once to add a blank space, then add the word single to tell GRUB to boot into single-user Linux mode. The result should look like the following:
ro root=LABEL=/ single
4.) Press [Enter] and GRUB will boot single-user Linux mode. After it finishes loading, you will be presented with a shell prompt similar to the following:
sh-2.05b#
5.) You can now change the root password by typing
passwd root