Server for NIS can operate in a master mode or subordinate mode. (If Server for NIS is used in a domain, the master server in the domain must be Server for NIS.) In UNIX, the primary difference between the two is that both subordinate and master servers can read map data, while only the master server can update maps. Additionally, the master Network Information Service (NIS) server provides periodic updates of the maps to subordinate servers.
In Windows with Server for NIS, because the data is stored in Active Directory, both master and subordinate servers share the same replicated Active Directory database. This makes them peers as far as map updates or write access are concerned. Server for NIS in either master mode or subordinate mode will allow updates to Network Information Service (NIS) map data stored in Active Directory. Changes to Active Directory on any of these servers are propagated to other Servers for NIS in the domain by the Active Directory synchronization mechanism.
Although these servers run as peers for data updates, there must still be only one master server as far as the UNIX subordinate servers and UNIX clients are concerned. UNIX subordinate servers will continue to receive map updates from the Server for NIS that is designated as the master server. Similarly, they will continue to send passwd changes only to the master server.
For information about changing a subordinate server to a master server, see To change a subordinate (slave) server to a master server.