Finding out on how you can change or update your Ubuntu root password, following is a simple trick for your Ubuntu root login.

Ubuntu Root Password

To log in as a root user in Ubuntu for the first time, you have to change or update your ubuntu root password. Even though, if you have access to use sudo command, you can use that user account, because sudo means super user do, means you can use your account as a super user or administrative account, if you have access to sudo.

However, if you still want to change your Ubuntu root password, which is not actually recommended, then here is a simple way of changing or assigning Ubuntu root password.

Simply goto the terminal ( Applications -> Accessories -> Terminal ) and enter:

sudo passwd root

It will prompt you to enter your password, more than one time.

Ubuntu Root Login

You can now easily login as your root account by the following command:

su root

and enter your new Ubuntu root password, to access and log in as root account.

Important Note

Please note that root user is disabled in Ubuntu by default, and it is like risky enabling the root user. For more details, you can check out the following url, which may help you in fulfilling your needs without enabling the root user:
https://help.ubuntu.com/community/RootSudo