In the earlier chapters, we explored various facts and functions that Puppet provides out-of-the-box. You may recall that, in Chapter 3, My First Puppet Module, we created a variable called $fact_list (line 3 in the webapp class), and we used it to store values of facts $::ipaddress_eth1 and $::uptime. These two facts are built into Puppet. Once we declared the $fact_list variable, we created a file resource with the content attribute that used the template function (line 7 in the webapp class) to populate the content of the file. The template function is a commonly used function that comes bundled with Puppet.

When you start using Puppet on a regular basis, you soon realize that the built-in facts and functions may not be sufficient to build configurations you want to build. Luckily, custom facts and functions are quick and easy to write yourself.

This chapter will focus on how to extend Puppet beyond the built-in functionality. We will learn how to create your...