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151 lines
5.1 KiB
ReStructuredText
.. _tutorial-states-part-2:
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=========================================================
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States tutorial, part 2 - More Complex States, Requisites
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=========================================================
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.. note::
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This tutorial builds on topics covered in :ref:`part 1 <states-tutorial>`. It is
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recommended that you begin there.
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In the :ref:`last part <states-tutorial>` of the Salt States tutorial we covered the
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basics of installing a package. We will now modify our ``webserver.sls`` file
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to have requirements, and use even more Salt States.
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Call multiple States
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====================
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You can specify multiple :ref:`state-declaration` under an
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:ref:`id-declaration`. For example, a quick modification to our
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``webserver.sls`` to also start Apache if it is not running:
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.. code-block:: yaml
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:linenos:
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:emphasize-lines: 4,5
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apache:
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pkg.installed: []
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service.running:
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- require:
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- pkg: apache
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Try stopping Apache before running :py:func:`state.apply
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<salt.modules.state.apply_>` once again and observe the output.
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.. note::
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For those running RedhatOS derivatives (Centos, AWS), you will want to specify the
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service name to be httpd. More on state service here, :mod:`service state
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<salt.states.service>`. With the example above, just add "- name: httpd"
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above the require line and with the same spacing.
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Require other states
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====================
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We now have a working installation of Apache so let's add an HTML file to
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customize our website. It isn't exactly useful to have a website without a
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webserver so we don't want Salt to install our HTML file until Apache is
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installed and running. Include the following at the bottom of your
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``webserver/init.sls`` file:
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.. code-block:: yaml
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:linenos:
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:emphasize-lines: 7,11
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apache:
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pkg.installed: []
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service.running:
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- require:
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- pkg: apache
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/var/www/index.html: # ID declaration
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file: # state declaration
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- managed # function
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- source: salt://webserver/index.html # function arg
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- require: # requisite declaration
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- pkg: apache # requisite reference
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**line 7** is the :ref:`id-declaration`. In this example it is the location we
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want to install our custom HTML file. (**Note:** the default location that
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Apache serves may differ from the above on your OS or distro. ``/srv/www``
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could also be a likely place to look.)
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**Line 8** the :ref:`state-declaration`. This example uses the Salt :mod:`file
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state <salt.states.file>`.
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**Line 9** is the :ref:`function-declaration`. The :func:`managed function
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<salt.states.file.managed>` will download a file from the master and install it
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in the location specified.
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**Line 10** is a :ref:`function-arg-declaration` which, in this example, passes
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the ``source`` argument to the :func:`managed function
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<salt.states.file.managed>`.
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**Line 11** is a :ref:`requisite-declaration`.
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**Line 12** is a :ref:`requisite-reference` which refers to a state and an ID.
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In this example, it is referring to the ``ID declaration`` from our example in
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:ref:`part 1 <states-tutorial>`. This declaration tells Salt not to install the HTML
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file until Apache is installed.
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Next, create the ``index.html`` file and save it in the ``webserver``
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directory:
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.. code-block:: html
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<!DOCTYPE html>
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<html>
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<head><title>Salt rocks</title></head>
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<body>
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<h1>This file brought to you by Salt</h1>
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</body>
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</html>
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Last, call :func:`state.apply <salt.modules.state.apply_>` again and the minion
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will fetch and execute the :ref:`highstate <running-highstate>` as well as our
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HTML file from the master using Salt's File Server:
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.. code-block:: bash
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salt '*' state.apply
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Verify that Apache is now serving your custom HTML.
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.. admonition:: ``require`` vs. ``watch``
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There are two :ref:`requisite-declaration`, “require”, and “watch”. Not
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every state supports “watch”. The :mod:`service state
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<salt.states.service>` does support “watch” and will restart a service
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based on the watch condition.
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For example, if you use Salt to install an Apache virtual host
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configuration file and want to restart Apache whenever that file is changed
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you could modify our Apache example from earlier as follows:
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.. code-block:: yaml
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:emphasize-lines: 1,2,3,10,11
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/etc/httpd/extra/httpd-vhosts.conf:
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file.managed:
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- source: salt://webserver/httpd-vhosts.conf
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apache:
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pkg.installed: []
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service.running:
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- watch:
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- file: /etc/httpd/extra/httpd-vhosts.conf
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- require:
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- pkg: apache
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If the pkg and service names differ on your OS or distro of choice you can
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specify each one separately using a :ref:`name-declaration` which explained
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in :ref:`Part 3 <tutorial-states-part-3>`.
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Next steps
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==========
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In :ref:`part 3 <tutorial-states-part-3>` we will discuss how to use includes, extends, and
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templating to make a more complete State Tree configuration.
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