.. _intro_modules:

Introduction to modules
=======================

Modules (also referred to as "task plugins" or "library plugins") are discrete units of code that can be used from the command line or in a playbook task. Ansible executes each module, usually on the remote target node, and collects return values.

You can execute modules from the command line::

    ansible webservers -m service -a "name=httpd state=started"
    ansible webservers -m ping
    ansible webservers -m command -a "/sbin/reboot -t now"

Each module supports taking arguments.  Nearly all modules take ``key=value``
arguments, space delimited.  Some modules take no arguments, and the command/shell modules simply
take the string of the command you want to run.

From playbooks, Ansible modules are executed in a very similar way::

    - name: reboot the servers
      action: command /sbin/reboot -t now

Which can be abbreviated to::

    - name: reboot the servers
      command: /sbin/reboot -t now

Another way to pass arguments to a module is using YAML syntax also called 'complex args' ::

    - name: restart webserver
      service:
        name: httpd
        state: restarted

All modules return JSON format data. This means modules can be written in any programming language. Modules should be idempotent, and should avoid making any changes if they detect that the current state matches the desired final state. When used in an Ansible playbook, modules can trigger 'change events' in the form of notifying 'handlers' to run additional tasks.

Documentation for each module can be accessed from the command line with the ansible-doc tool::

    ansible-doc yum

For a list of all available modules, see the :ref:`Module Docs <modules_by_category>`, or run the following at a command prompt::

    ansible-doc -l


.. seealso::

   :ref:`intro_adhoc`
       Examples of using modules in /usr/bin/ansible
   :ref:`working_with_playbooks`
       Examples of using modules with /usr/bin/ansible-playbook
   :ref:`developing_modules`
       How to write your own modules
   :ref:`developing_api`
       Examples of using modules with the Python API
   `Mailing List <https://groups.google.com/group/ansible-project>`_
       Questions? Help? Ideas?  Stop by the list on Google Groups
   `irc.freenode.net <http://irc.freenode.net>`_
       #ansible IRC chat channel
