When installing Ansible, the user will also receive a very handy set of modules. This set is called a module library. It is a list of predefined functions and actions to be called when using Ansible, either via ad hoc commands or by running playbooks. An Ansible user is not limited to the predefined Ansible modules; they can easily write their own using Python and JSON scripting. The modules that come with the installation of Ansible might be referred to as task plugins or library plugins, but do not mistake these for the actual Ansible plugins, which are the scripts that allow Ansible to interact with other systems, a subject for another chapter.

The Ansible module library comes with its own machine library. Use the ansible-doc command followed by the name of the module to find out more about how it is used and what its output variables are:

ansible-doc apt

To list all the available modules, use the -l option:

ansible-doc -l

Using modules is very simple. You need to identify the name of the module, then input its arguments if required. Not all modules require argument input (the ping module, for example, doesn't require this) but most do. For other modules, inputting arguments is optional and might allow you to personalize the action, such as in the case of the Windows reboot module. As an example, let's look at executing modules in both ad hoc and playbook mode.