~ CHAPTER 9: CORE SYSTEM SERVICES ~

Linux system has five core services: init, inetd, xinetd, syslog, and cron.

init. Always has a process ID of 1. The mysterious force that tells init when to change runlevels

is actually the telinit command.

inetd. Not in version 7.0? The role of inetd is as a “supervisor” for other network server-related

processes, such as telnet and ftp. The directory is /etc/inetd.conf. The file is empty the inetd.conf.

But xinetd.conf. Another file used instead of inetc.

Security for inetd.conf. You’ll find that in most installations of Linux, many services are turned on

by default. If your system will be available to the Internet at large, the first thing you’ll want to do is

turn everything off! Never assume that just because your system is unadvertised to the public, other

people won’t find it.

Needs curly brackest { }syslogd. The syslogd daemon provides a standardized means of

performing logging. Many other UNIXs employ a compatible daemon, thus providing a means for

cross-platform logging over the network.

The log files that syslogd stores to are straight text files, usually stored in the /var/log directory.

Each log entry consists of a single line containing the date, time, hostname, process name, process

PID, and the message form that process.

Linux logs all of the processes, straight text files.

The location to which syslogd can send log messages is also quite flexible. It can save messages to

files and send messages to FIFOs, to a list of users, or to a master log host.

Cron. The cron program allows any user in the system to schedule a program to run on any date, at

any time, or on a particular day of week, down to the minute. It is a scheduler. It is a command-line

tool.

Create allow & deny files in /etc/cron.allow and /etc/cron.deny files.

SUMMARY:

This chapter has 5 core services that come with every Linux system.

These services do not require network support and can vary from host to host, making them very

useful, since they can work regardless of whether or not the system is in multiuser mode.

init is the father of all processes in the system with a PID of 1. It also controls runlevels and can be

configured through the /etc/iniitab file.

inetd is the superserver that listens to server requests on behalf of a large number of smaller, less

frequently sued services.

All services have a d on the end of them to signify that they are a service.

xinetd is a “new” version of the classic inetd superserver that offers more configuration options and

better built-in security. Its configuration file is /etc/xinetd.conf.

syslog Is the system-wide logging daemon. Along with log entries generated by the system, syslog

can accept log messages over the network (so long as you enable that feature). Its configuration file

s /etc/syslog.conf.