How to enable and disable root user in Ubuntu 14.04 LTS

If you ever need to enable the root user in Ubuntu 14.04 LTS linux installation, you can do so as follows:
Open a terminal window and type the following commands:
$ sudo su -c <enter>
# passwd root <enter>

Enter a strong password and restart the computer.

To make sure that you can login as root, open a new terminal window and at the $ prompt, enter:
$ su <enter>
Enter the root password. If you get the # prompt, then you are logged in as the root user.

Now you can manage the system by explicitly logging in as root user.

There could be a need to disable root login. You can do that in a terminal window as follows:
$ sudo passwd -dl root <enter>