“Network administrators frequently use the Lightweight Directory
Access Protocol (LDAP) to implement a centralized directory server.
You can use LDAP to authenticate users in Apache. Two popular open
source LDAP solutions are OpenLDAP and Red Hat Directory Server.
According to the Apache documentation, Novell LDAP and iPlanet
Directory Server are also supported. This article focuses on
OpenLDAP, but the concepts and examples should be applicable to the
“LDAP was designed as a simplified version of the ITU-T X.500
directory specification. The default set of schemas contain all of
the information you would find in traditional Linux system files
such as /etc/passwd and /etc/group, or Sun’s Network Information