Essential Mac OS X Panther Server Administration

Chapter 10. xinetd

Early in Unix history, hardware resources were expensive: so expensive, in fact, that several users typically shared one really big piece of hardware. So expensive that every single process running on that hardware was audited meticulously, so that no extraneous processes took up system resources. Out of this conservation-focused environment, inetd, xinetd ’s precursor, was born. The large, shared computing environments of the time typically supported several network services: finger, telnet, ftp, and rlogin, among others. Rather than having to keep all of these daemons running all of the time, inetd would listen on the service’s port and then start the appropriate daemon when connections were established, thus conserving resources and managing access to the system.

inetd served the Unix world well; it was a central point through which connections to the system were established. And it made sense in a time of increasing security concerns to add some basic support for access controls into the infrastructure, and over time, as hardware resources became cheaper, this became inetd’s central role—providing security for the services it managed.

This evolution eventually produced xinetd, a completely rewritten facility that, like inetd, managed a set of services in the OS. Unlike inetd though, xinetd is specifically architected with security in mind. It plays an increasing role in Panther Server as well as Panther client, and like much of the OS, supports a deep set of ...