Summary

Classes and defined types are the essential tools to create reusable Puppet code. While classes hold resources that must not be repeated in a manifest, the define is capable of managing a distinct set of adapted resources upon every invocation. It does that by leveraging the parameter values it receives. While classes do support parameters as well, there are some caveats to bear in mind.

To use defined types in your manifest, you declare instances just like resources of native types. Classes are mainly used through the include statement, although there are alternatives such as the class { } syntax or the contain function.

There are also some ordering issues with classes that the contain function can help mitigate.

In theory, classes and defines suffice to build almost all the manifests that you will ever need. In practice, you will want to organize your code into larger structures. The next chapter will show you how to do exactly that, and introduce you to a whole range of useful functionality beyond it.