Re: the root of the directory tree

i'm working on a lan with students, teachers, some guests and a pair of administrators. i need that everyone can authenticate himself on the lan. there are some computers in a room and i want they will be powered on will appear a display to log in. the same thing for every computer that will be connect to our local network. every user will have his permissions to visit different sites, to see server resources, etc. i don't know how prepare this but for the moment am preparing the server populating it with every user.

Take a look at SSSD, https://fedorahosted.org/sssd/ . It will allow you to setup much more robust environment.