User authentication for logins is generally a no brainer. You setup users on the local system and off you go... nothing to it. However, if you're on a LAN and you want to have a centralized "repository" of users, you will likely be looking at some method of distributing user information across the LAN. This has a few distinct advantages, the primary being all user authentication is centralized. This means that users have the same password on each system in the LAN, and if they change their password, the password is seamlessly changed everywhere. This provides the advantage of giving consistency to user authentication on the LAN. Users retain the same userid, groupid, password, and other information. This can be problematic if you assign users different levels of access on different machines, but if you permit the same access on all systems, this is an easy way to do it. Regardless, with sudo, you can fine-tune privileged access on a host-by-host basis as well.

Traditionally, NIS (Network Information Services, aka YP (Yellow Pages)) was used to provide this sort of information. NIS is an RPC-based protocol similar to NFS. And while NIS may work well enough in most cases, it doesn't work well in all cases (personal experience here has shown NIS to be anything but reliable). However, there is another choice, and that choice is LDAP. Mandrake Linux provides OpenLDAP and this is the starting block of what is required for a distributed authentication system.

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