Ubuntu server 12.04 on AWS - How does the passwordless sudo work for the ubuntu user?

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http://askubuntu.com – tl;dr: How does the ubuntu user on the AWS images for Ubuntu Server 12.04 have passwordless sudo for all commands when there is no configuration for it in `/etc/sudoers'? I'm using Ubuntu server 12.04 on Amazon. I want to add a new user that has the same behaviour as the default ubuntu user. Specifically I want passwordless sudo for this new user. So I've added a new user and went to edit /etc/sudoers (using visudo of course). From reading that file it seemed like the default ubuntu user was getting it's passwordless sudo from being a member of the admin group. So I added my new user to tha (HowTos)