I'm using Ubuntu 14.04 on my server.

Good security practice recommends disabling root.

I've created a non-root-user with a non-root-user's-password in the sudo group.

So far so good.

Here's my question.

Usually, when I do sudo, Ubuntu asks for the root password. If I disable root, then what will happen when I do sudo? Will it still ask for a password? If yes, then which password will it ask for? If no, then how will it double-check that I am a legitimate sudo user?