 | Level: Intermediate Martin Streicher (martin.streicher@gmail.com), Chief Technology Officer, McClatchy Interactive
07 Oct 2008 To leverage round-the-clock computing, tasks must run at all hours of the day. You could
punctuate your sleep with waking interludes to log in and run this command or that
command on
dozens of machines, or you can enjoy your forty winks and turn the work over to the
ubiquitous cron, a daemon, or perennial process, to execute commands on a schedule. From
very often to every so often, cron happily minds the clock and runs jobs day or night. Learn
how to configure and maintain cron, and discover just some of its many uses.
In this tutorial
Learn how to create, schedule, and manage cron jobs
and how to define timetables to control job frequency, from once per minute to
once per year. Additionally, learn how to limit access to cron
to prevent abuse and how to use other utilities in tandem with cron
to automate common maintenance tasks.
Prerequisites
This tutorial is written for users and systems administrators of UNIX® (and UNIX-like)
systems. To follow this tutorial, you should have a general familiarity with a
command-line shell and shell scripting. Some experience installing and
configuring software on UNIX is also helpful.
System requirements
To run the examples in this tutorial, you need a UNIX computer. If you want to
configure system-wide cron jobs, you also need root
access. The examples shown in this tutorial are based on Vixie
cron, which is used widely on modern UNIX systems,
running on Ubuntu Desktop Linux® version 8.04.1. Other versions of
cron are similar to Vixie; check the documentation
for your UNIX system for specifics.
To view the demos included in this tutorial, JavaScript must be enabled in your browser and Macromedia Flash Player 6 or higher must be installed. You can download the latest Flash Player at http://www.macromedia.com/go/getflashplayer/.
Duration
1 hour
Formats html, pdf
About this tutorial
This tutorial explains how to configure and maintain cron,
the job scheduler found on almost all UNIX® machines. Additionally, this
lesson demonstrates just some of the many applications of cron.
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