=========================================================
States tutorial, part 2 - More Complex States, Requisites
=========================================================

.. note:: 

    This tutorial builds on topics covered in :doc:`part 1 <states_pt1>`. It is
    recommended that you begin there.

In the :doc:`last part <states_pt1>` of the Salt States tutorial we covered the
basics of installing a package. We will now modify our ``webserver.sls`` file
to have requirements, and use even more Salt States.

Call multiple States
====================

You can specify multiple :ref:`state-declaration` under an
:ref:`id-declaration`. For example, a quick modification to our
``webserver.sls`` to also start Apache if it is not running:

.. code-block:: yaml
    :linenos:
    :emphasize-lines: 4,5

    apache:
      pkg:
        - installed
      service:
        - running
        - require:
          - pkg: apache

Try stopping Apache before running ``state.highstate`` once again and observe
the output.

Require other states
====================

We now have a working installation of Apache so let's add an HTML file to
customize our website. It isn't exactly useful to have a website without a
webserver so we don't want Salt to install our HTML file until Apache is
installed and running. Include the following at the bottom of your
``webserver/init.sls`` file:

.. code-block:: yaml
    :linenos:
    :emphasize-lines: 7,11

    apache:
      pkg:
        - installed
      service:
        - running
        - require:
          - pkg: apache

    /var/www/index.html:                        # ID declaration
      file:                                     # state declaration
        - managed                               # function
        - source: salt://webserver/index.html   # function arg
        - require:                              # requisite declaration
          - pkg: apache                         # requisite reference

**line 9** is the :ref:`id-declaration`. In this example it is the location we
want to install our custom HTML file. (**Note:** the default location that
Apache serves may differ from the above on your OS or distro. ``/srv/www``
could also be a likely place to look.)

**Line 10** the :ref:`state-declaration`. This example uses the Salt :mod:`file
state <salt.states.file>`.

**Line 11** is the :ref:`function-declaration`. The :func:`managed function
<salt.states.file.managed>` will download a file from the master and install it
in the location specified.

**Line 12** is a :ref:`function-arg-declaration` which, in this example, passes
the ``source`` argument to the :func:`managed function
<salt.states.file.managed>`.

**Line 13** is a :ref:`requisite-declaration`.

**Line 14** is a :ref:`requisite-reference` which refers to a state and an ID.
In this example, it is referring to the ``ID declaration`` from our example in
:doc:`part 1 <states_pt1>`. This declaration tells Salt not to install the HTML
file until Apache is installed.

Next, create the ``index.html`` file and save it in the ``webserver``
directory:

.. code-block:: html

    <html>
        <head><title>Salt rocks</title></head>
        <body>
            <h1>This file brought to you by Salt</h1>
        </body>
    </html>

Last, call :func:`state.highstate <salt.modules.state.highstate>` again and the
minion will fetch and execute the highstate as well as our HTML file from the
master using Salt's File Server:

.. code-block:: bash

    salt '*' state.highstate

Verify that Apache is now serving your custom HTML.

.. admonition:: ``require`` vs. ``watch``

    There are two :ref:`requisite-declaration`, “require” and “watch”. Not
    every state supports “watch”. The :mod:`service state
    <salt.states.service>` does support “watch” and will restart a service
    based on the watch condition.

    For example, if you use Salt to install an Apache virtual host
    configuration file and want to restart Apache whenever that file is changed
    you could modify our Apache example from earlier as follows:

    .. code-block:: yaml
        :emphasize-lines: 1,2,3,4,11,12

        /etc/httpd/extra/httpd-vhosts.conf:
          file:
            - managed
            - source: salt://webserver/httpd-vhosts.conf

        apache:
          pkg:
            - installed
          service:
            - running
            - watch:
              - file: /etc/httpd/extra/httpd-vhosts.conf
            - require:
              - pkg: apache

    If the pkg and service names differ on your OS or distro of choice you can
    specify each one separately using a :ref:`name-declaration` which explained
    in :doc:`Part 3 <states_pt3>`.

Next steps
==========

In :doc:`part 3 <states_pt3>` we will discuss how to use includes, extends and
templating to make a more complete State Tree configuration.
