Network Information Service
As mentioned earlier in this chapter, Sun developed Network Information Service (NIS) as a client/server system that allows for the sharing of information on a network, including 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, whereas NIS+ more closely 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. It also uses a concept called maps for storing data using a simple keyword/data concept. NIS+ uses a more traditional database format with tables containing multicolumned 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.
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