Scenario: You’re trying to execute a command with sudo:

$sudo ./utstart install

We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

[sudo] password for www-data:
www-data is not in the sudoers file.  This incident will be reported.

Adding a user to sudoers:

usermod -a -G sudo username

As root:

usermod -a -G sudo www-data

Note that sudo rights will not be enabled for any users currently logged in. They will need to logout before they can use sudo to gain root rights.