This chapter will focus on how to write and test custom modules. We've already discussed how modules work and how to use them within your tasks. Well, just for a quick recap, a module in Ansible is a piece of code, which is transferred and executed on your remote host every time you run an Ansible task (it can also run locally if you've used local_action).
From my experience, I've seen custom modules being written whenever a certain functionality needs to be exposed as a first-class task. The same functionality could have been achieved without the module, but it would have required a series of tasks with existing modules to accomplish the end goal and often also command and shell modules. For example, let's say you wanted to provision a server via Preboot Execution Environment (PXE). Without a custom module, you would have probably used a few shell or command tasks to accomplish the same. However, with a custom module, you would just pass the required...