Linux Network Administrator's Guide, 3rd Edition

Chapter 10. Important Network Features

After successfully setting up IP and the resolver (DNS), you then must look at the services you want to provide over the network. This chapter covers the configuration of a few simple network applications, including the inetd and xinetd servers and the programs from the rlogin family. We’ll also deal briefly with the Remote Procedure Call interface, upon which services like the Network File System (NFS) are based. The configuration of NFS, however, is more complex and is not described in this book.

Of course, we can’t cover all network applications in this book. If you want to install one that’s not discussed here, please refer to the manual pages of the server for details.

The inetd Super Server

Programs that provide application services via the network are called network daemons. A daemon is a program that opens a port, most commonly a well-known service port, and waits for incoming connections on it. If one occurs, the daemon creates a child process that accepts the connection, while the parent continues to listen for further requests. This mechanism works well but has a few disadvantages; at least one instance of every possible service that you wish to provide must be active in memory at all times. In addition, the software routines that do the listening and port handling must be replicated in every network daemon.

To overcome these inefficiencies, most Unix installations run a special network daemon, what you might consider a “super server.” ...