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States tutorial, part 2

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

In the last Salt States tutorial we covered the basics of installing a package. In this tutorial we will modify our webserver.sls file to be more complicated, have requirements, and use even more Salt States.

Call multiple States

You can specify multiple :term:`state declarations <state declaration>` under an :term:`ID declaration`. For example, a quick modification to our webserver.sls to also start Apache if it is not running:

apache:
  pkg:
    - installed
  service:
    - running

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

Expand the SLS module

As you have seen, sls modules are appended with the file extension .sls and are referenced by name starting at the root of the state tree. An SLS module can be also defined as a directory. Demonstrate that now by creating a directory named webserver and moving and renaming webserver.sls to webserver/init.sls. Your state directory should now resemble:

|- top.sls
`- webserver/
   `- init.sls

Organizing SLS modules

You can place additional .sls files in a state file directory. This affords much cleaner organization of your state tree on the filesystem. For example, if we created a webserver/django.sls file that module would be referenced as webserver.django.

In addition, States provide powerful includes and extending functionality which we will cover in :doc:`Part 3 <states_pt3>`.

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:

apache:
  pkg:
    - installed
  service:
    - running

/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 7 is the :term:`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 8 the :term:`state declaration`. This example uses the Salt :mod:`file state <salt.states.file>`.

Line 9 is the :term:`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 10 is a :term:`function arg declaration` which, in this example, passes the source argument to the :func:`managed function <salt.states.file.managed>`.

Line 11 is a :term:`requisite declaration`.

Line 12 is a :term:`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:

<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:

salt '*' state.highstate

Verify that Apache is now serving your custom HTML.

require vs. watch

There are two :term:`requisite declarations <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:

/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

If the pkg and service names differ on your OS or distro of choice you can specify each one separately using a :term:`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 hugely complicated State Tree configurations dead-simple.