How to enable/disable root account on Ubuntu

If you want to enable root account (which is not recommended) enter the following command:
sudo passwd root
This will prompt for a new root password and once you confirm it, you can start using the root account to login.
If you want to disable root account in ubuntu you need to lock the root account by using the following command
sudo passwd -l root
If you want to work on a root console you’d better use the following command
sudo -i