System Services - inetd and xinetd

System Services - inetd and xinetd

Linux is full of daemons. No, no, no … put the phone down. You don’t need the local priest to perform an exorcism on you Linux box. Daemons in Linux are good things. Good daemons? Yep. inetd and xinetd are just two of them.

Daemons in Linux are programs that run independent of the terminal (tty) that started them. They’re started in a tty but release control of the terminal, communicating with the system only through Interprocess Communications (IPC), by writing to log files, or by adding to disk files. Daemons use very few resources but serve, in many cases, as the brains behind many crucial Linux processes.

inetd and xinetd are two of these beneficial daemons. Serving as the “traffic cop” for server-based network processes, inetd listens for incoming connections such as ftp and telnet, checks an internal list of network-related programs in /etc/inted.conf, and passes off those incoming commands to the appropriate program. These programs generally don’t receive so many requests as to require them to be resident in memory all the time. In other words, inetd resides in memory on behalf of a full set of programs that may or may not be used. It’s a very efficient approach that requires minimal system overhead to maintain maximum system power.

xinetd serves much the same purpose as inetd. It is, in fact, a variant on inetd introduced by RedHat and adopted by some of the other distributions. It does serve the same purpose, but requires a different configuration file format. Most Unix-like distros, Slackware included, still rely on the classic inetd format.

Tomorrow, we’ll talk about the simple elegant structure of the /etc/inetd.conf file and how it controls inetd in providing this valuable service.

See … you can forget all the campfire ghost stories. Daemons really can be good.