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http://directory.fedoraproject.org/
A directory server provides a centralized directory service for your intranet, network, and/or extranet with information that systems and client applications can “lookup” information and is somewhat analogous to a phone book. A directory server can typically integrate with existing systems and applications and acts as a centralized repository for the consolidation of employee, customer, supplier, partner, or any other information you wish to make available. You can extend Directory Server to manage user profiles and preferences as well as user authentication. Why is a directory server important in a book geared toward a discussion of SOX? We use LDAP to provide a single point of user/group authentication for systems and applications and it is these features that we focus on for our SOX examples.