LDAP

http://www.debuntu.org/ldap-server-and-linux-ldap-clients

http://wiki.freaks-unidos.net/linux%20ldap%20howto

http://www.yolinux.com/TUTORIALS/LDAP_Authentication.html

http://tldp.org/HOWTO/LDAP-HOWTO/authentication.html

http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch31_:_Centralized_Logins_Using_LDAP_and_RADIUS