The main purpose of NIS is centralizing the authentication

database.

For ex:

Usually when a user try to login to the machine it will

contact the passwd, shadow and group files for user’s

authentication, in case of user requires to access his/her

account across the network we need to update users

information all these files in each machine in the network.

It is bit tricky to organize multiple users’ info in all

the machines in the network.

NIS server will act as central server for user

authentication and all other machines will contact the NIS

server for the user’s authentication info.

Make sure all the machines in your network should be in the

same domain. NIS will work only in single domain.