passwd root

How to change root password in Ubuntu
The procedure to change the root user password on Ubuntu Linux:

Type the following command to become root user and issue passwd:
sudo -i
passwd
OR set a password for root user in a single go:
sudo passwd root
Test it your root password by typing the following command:
su -

    Step 1: Open a Terminal Window.
    		Right-click the desktop, then left-click Open in terminal.
            Alternately, you can click Menu > Applications > Accessories > Terminal.
    Step 2: Change Your Root Password.
    		In the terminal window, type the following:
            	- sudo passwd root.