Network Information Service

As mentioned earlier, Sun developed a product that was originally called Yellow Pages, but the name was later changed due to a trademark owned by British Telecom. Sun's product was Network Information Service (NIS), a client/server system that allows for the sharing of information on a network that includes not only hostnames and addresses, but also other information, such as password files. The goal of NIS is to reduce administrative overhead problems associated with having multiple copies of files on hosts throughout the network.

NIS is based on a flat namespace design. Sun has now released NIS+, which resembles the Domain Name System in its hierarchical structure. NIS+ uses a concept of NIS domains, which might or might not be paired with DNS domains. NIS uses a concept called maps for storing data. Maps use a simple keyword/data concept. NIS+ uses a more traditional database format with tables containing multi-columned rows of data.

NIS is mentioned in this chapter not because it is a name resolution mechanism, but because on many Unix networks, NIS is responsible for keeping synchronized other files that perform name resolution. If you use NIS (or NIS+), I recommend you become familiar with its installation and configuration. Security on Unix systems can be a difficult task if you just install NIS and forget about it. You need to understand how it works, and you should consider the security implications of keeping important information on different servers throughout the network.