When your entire network infrastructure consists of a computer on a desk in your living room, management of your user accounts and preferences is simple and straightforward. Your account and data are stored in one physical location. Add a second computer and maybe a laptop for travel, and you now have two or three sets of user accounts, passwords, and data.
Now multiply the computers by tens, hundreds, or thousands, and you see how managing users and data becomes beyond cumbersome in a large network. The solution is to create network directory services to aid managing many computer systems and users. A network directory is a shared list of users, accounts, and other resources that reside on the network. From a single location, you can manage a directory of all this information for hundreds of users. A directory can reside in one server computer or can be handled by dozens of servers on a large network.
Directory services also handle the job of authenticating users, which confirms the identity of users logging in from a client computer. Directory services handles authentication for other services, such as e-mail or file sharing, or to the entire network, or for the entire network at once — known as single sign-on.
Mountain Lion Server can host a directory for your network of Mac, Windows, and Linux computers. It can also make use of a directory residing on other servers. And it can help integrate your Mac users into a Windows-based Active Directory network. ...