Say you got a new server set up on a VPS system, such as DigitalOcean. These servers often are set up with a root account and not a non-privileged account by default. We all know this is a _bad_ thing, so once you have created a user that you’d like to make the admin user, who has sudo access, you can disable the ability to log in as root by issuing:
sudo passwd -l root
Note that this does not disable the account, merely disables logging in directly. You can always become root by issuing sudo -s to obtain a root shell 🙂