Remove ec2-user default privilege

1. useradd to add a new user account
2. Create password for the new user, add it to the sudoer list
3. Enable PasswordAuthentication in /etc/ssh/sshd_conifg
4. Change root password
5. Lock ec2-user: passwd -l ec2-user
6. Delete /etc/sudoers.d/xx
7. Now the ec2-user has no root permission

Reference:

http://blog.braini.ac/?p=73