In some environments, a Network Information Server (NIS) provides centralized storage and distribution of information that needs to be known throughout the network. In a typical NIS environment, one or more NIS servers are used to centrally manage a set of database maps that correspond to the system configuration files that are commonly found on UNIX systems. For example, there are NIS maps that correspond to the /etc/passwd, /etc/group, /etc/hosts, and /etc/services files. The maps provide the centralized information to a given set of computers that make up a NIS domain.
Each NIS map corresponds to a specific configuration file, such as the /etc/passwd or /etc/hosts file, and consists of a set of keys and values, and a version number for the data. When computers on the network require information stored in NIS maps, they send a NIS client request to the NIS listening port to query the NIS server for the information.
When a computer needs the information stored in a NIS map, it runs the ypbind process to identify and connect to the NIS server best suited to respond to its requests. When the NIS server receives a request, it replies with the appropriate information from its set of NIS maps.