Apache: The Definitive Guide, 3rd Edition

Passwords

A password is only useful when there is a human in the loop to remember and enter it. Passwords are not useful between processes on the server. For instance, scripts that call the database manager will often have to quote a password. But since this has to be written into the script that anyone can read who has access to the server and is of no use to them if they have not, it does nothing to improve security.

However, services should have minimal access, and separate accounts should be used. SSH access with the associated encrypted keys should be necessary when humans do upgrades or perform maintenance activities.