In setting up an apache web server on my linux box, I've been told to make a separate user who has permission to use (and whose home directory is) the files in the /www directory. Additionally, I've made a mySQL user. Both of these users have the nologin attribute.
I have very little idea what I'm doing here, and I'm mostly doing testing via http://localhost, so I've been working mostly from my user account.
What I would like to know is as follows:
1) Generally, why do these users exist?
2) Does apache, mySQL or php access the privileges of these users?
3) Under what circumstances would I access the privileges of these users?
4) Why do they need the nologin attribute?
5) Any other relevant information that I didn't know to ask about.