Automating Linux and Unix System Administration (PDF)

CHAPTER 4 Configuring Systems with cfengine (S. 49-50)

So far we’ve been discussing automation in a general way. At this point we’ll move beyond single ad hoc measures to a more systematic and robust approach. While you certainly have the option of writing your own collection of automation scripts, we recommend you use a proven automation framework: cfengine.

Getting an Overview of cfengine

Cfengine is software you can use to automate changes on UNIX (and UNIX- like) systems. It is a high- level language that describes system state, not a general- purpose programming language such as Perl or a shell. It’s primarily declarative, meaning that the SA writes out a technical description instead of a list of low- level steps to accomplish the goal. It is high- level enough that someone familiar with UNIX concepts and usage can read a cfengine configuration and understand what is being done without any prior cfengine knowledge. The language drives what you should consider your personal software robot. This robot (called ) does your repetitive work for you while you move on to other tasks. In this chapter we’ll use the current version of cfengine at the time of this writing: version 2.2.7.

Defining cfengine Concepts

Cfengine was designed to save time and reduce errors though automation. Its second, related goal is to enable computer systems to self- correct errors. It might take you some time to set up and configure cfengine, but you will be happier when everything has been said and done. At first, performing a new task with cfengine might take longer than performing the same task manually. But when you upgrade the operating system and lose a change made under the old OS installation, you’ll be glad you used cfengine because it will simply perform the change again. Or, when you realize a few other systems need the same change,you can use cfengine to make this happen in seconds (by adding the new systems

Nathan Campi is a UNIX and Linux system administrator by trade, working as a UNIX operations manager in San Francisco. His system administration experience is almost entirely with companies with large-scale web operations based on open source software. In his copious free time, he enjoys jogging, watching spaghetti westerns, experimenting with Linux systems, and spending time with his family.

From the reviews:

"While automating a system is the dream of all sysadmins, there is such a thing as too much automation. Thankfully, this book recognises it. It covers just everything a sysadmin needs to know … . If you’re a sysadmin – get this book, you won’t be sorry. Highly recommended." (Paul F. Johnson, CVU/ ACCU/ Reviews, February, 2004)