How to reset password for root on Ubantu

Yes I have started learning Ubantu. I installed Ubantu8.1 desktop and during installation it ask me to create user name but never prompt me for root password. So once I logged in I was not sure what would be the root password.

When I did su ,it asked me for password.
So now I was in fix how to change password for root.

To change password /reset password
:~$ sudo sh

it will ask for current logged in user password

Then you will be in # prompt.

Type here passwd and it will change password for root