A server process makes the contents of the files available over the network.A server and its clients constitute an NIS "domain." Data files are preprocessed into database files by the Berkeley DB hashing library to improve the efficiency of lookups.
Note: In the early days, NIS was called Yellow Pages.
The user account is created only on the NIS server.
NIS clients download the necessary user name and password data from the NIS server to verify each user login.
Network Information Service (NIS) is used for keeping a centralized repository of users, hostnames and other useful information in a computer network.
In single server UNIX environments, the list of users and groups is usually kept in a file such as /etc/passwd.