Remove sudo privileges from a user (without deleting the user)

Question

If you give a user sudo privileges how can I remove the sudo privileges and make the user become just a regular user?

I used:

sudo adduser username sudo

Now I've changed my mind.

Answer 1

Just type

sudo deluser username sudo

This will remove the user named username from the group sudo.

Be careful not to remove the real adminuser from the sudo group.

Answer 2

You can also use gpasswd:

sudo gpasswd -d username sudo

This will remove username from group sudo.