Linux Network Administrators Guide
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Chapter 13. The Network Information System
- Table of Contents
- 13.1. Getting Acquainted with NIS
- 13.2. NIS Versus NIS+
- 13.3. The Client Side of NIS
- 13.4. Running an NIS Server
- 13.5. NIS Server Security
- 13.6. Setting Up an NIS Client with GNU libc
- 13.7. Choosing the Right Maps
- 13.8. Using the passwd and group Maps
- 13.9. Using NIS with Shadow Support
When you're running a local area network, your overall goal is usually to provide an environment for your users that makes the network transparent. An important stepping stone is keeping vital data such as user account information synchronized among all hosts. This provides users with the freedom to move from machine to machine without the inconvenience of having to remember different passwords and copy data from one machine to another. Data that is centrally stored doesn't need to be replicated, so long as there is some convenient means of accessing it from a network-connected host. By storing important administrative information centrally, you can make ensure consistency of that data, increase flexibility for the users by allowing them to move from host to host in a transparent way, and make the system administrator's life much easier by maintaining a single copy of information to maintain when required.
We previously discussed an important example of this concept that is used on the Internet—the Domain Name System (DNS). DNS serves a limited range of information, the most important being the mapping between hostname and IP address. For other types of information, there is no such specialized service. Moreover, if you manage only a small LAN with no Internet connectivity, setting up DNS may not seem to be worth the trouble.
This is why Sun developed the Network Information System (NIS). NIS provides generic database access facilities that can be used to distribute, for example, information contained in the passwd and groups files to all hosts on your network. This makes the network appear as a single system, with the same accounts on all hosts. Similarly, you can use NIS to distribute the hostname information from /etc/hosts to all machines on the network.
NIS is based on RPC, and comprises a server, a client-side library, and several administrative tools. Originally, NIS was called Yellow Pages , or YP, which is still used to refer to it. Unfortunately, the name is a trademark of British Telecom, which required Sun to drop that name. As things go, some names stick with people, and so YP lives on as a prefix to the names of most NIS-related commands such as ypserv and ypbind .
Today, NIS is available for virtually all Unixes, and there are even free implementations. BSD Net-2 released one that has been derived from a public domain reference implementation donated by Sun. The library client code from this release had been in the Linux libc for a long time, and the administrative programs were ported to Linux by Swen Thümmler.[1] An NIS server is missing from the reference implementation, though.
Peter Eriksson developed a new implementation called NYS.[2]
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