Hello I installed Ubuntu Server 12.04 on my machine and installed different apps like ejabberd(instant messaging server), openswan(vpn), davical(carddav,caldav). Is there a way to have centralized authentication to each app instead of creating new users within each of them. I plan to make users accounts for my friends so they can use it. But I don't want to have the accounts create directories in my hd like /home/user1 and I don't want the users to be able to ssh into the server.
I think it through PAM or maybe some database, I have been searching online but not sure how to phrase my question.