Just a quick post tonight. It is appropriate to give access to Apache, or Nginx, to the www-data user that has sites or applications deployed under their care. It is also appropriate limit www-data's access to the system as much as possible. The appropriate method by which to give access then is to add them to the sudoers file. Often, you may see the sudoers file used to permit a super user, of sorts, access to all of the system as a temporary root user. However, sudo is extremely powerful. Here is how you would give the www-data user access to only restart an Nginx server using the init scripts.
# Make a command alias Cmnd_Alias NGINX=/etc/init.d/nginx
# Give access, removing password requirement is optional www-data ALL=NOPASSWD: NGINX
And there we have it. Simply drop the NOPASSWD: section to require a password be used. Now, deployment utilities, like Capistrano can be setup to start, stop, and restart Nginx as the configuration changes. A very simple example to start Nginx with capistrano would be:
desc "Start Nginx" task :start, :roles => :web do run "/etc/init.d/nginx start" end
All in all, a good skill to have. I know I'll be re-reading the MAN pages for sudo in the coming days because there is much more sys-admin power to be found.