To add, edit or delete sudo users in putty/bash do the following
- Type visudo and press enter.
- Navigate using the arrow keys to where you want to edit.
- Press insert to enter edit mode.
- Make your changes. It is very important that you use tabs and spaces correctly.
- Press esc to exit edit mode.
- Type :wq and press enter. I remember this command as “write quit”
This is a pretty simple process, but very easy to forget when you only make changes sporadically.