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  <div class="section" id="playbooks">
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<h1>Playbooks<a class="headerlink" href="#playbooks" title="Permalink to this headline">¶</a></h1>
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<p>Playbooks are a completely different way to use ansible than in task execution mode, and are
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particularly awesome.   Simply put, playbooks are the basis for a really simple
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configuration management and multi-machine deployment system,
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unlike any that already exist, and one that is very well suited to deploying complex applications.</p>
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<p>Playbooks can declare configurations, but they can also orchestrate steps of
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any manual ordered process, even as different steps must bounce back and forth
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between sets of machines in particular orders.  They can launch tasks
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synchronously or asynchronously.</p>
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<p>While you might run the main /usr/bin/ansible program for ad-hoc
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tasks, playbooks are more likely to be kept in source control and used
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to push out your configuration or assure the configurations of your
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remote systems are in spec.</p>
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<p>Let’s dive in and see how they work.  As you go, you may wish to open
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the <a class="reference external" href="https://github.com/ansible/ansible/tree/devel/examples/playbooks">github examples directory</a> in
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another tab, so you can apply the theory to what things look like in practice.</p>
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<div class="section" id="playbook-language-example">
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<h2>Playbook Language Example<a class="headerlink" href="#playbook-language-example" title="Permalink to this headline">¶</a></h2>
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<p>Playbooks are expressed in YAML format and have a minimum of syntax.
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Each playbook is composed of one or more ‘plays’ in a list.</p>
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<p>The goal of a play is map a group of hosts to some well defined roles, represented by
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things ansible called tasks.  At the basic level, a task is nothing more than a call
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to an ansible module, which you should have learned about in earlier chapters.</p>
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<p>By composing a playbook of multiple ‘plays’, it is possible to
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orchestrate multi-machine deployments, running certain steps on all
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machines in the webservers group, then certain steps on the database
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server group, then more commands back on the webservers group, etc.</p>
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<p>For starters, here’s a playbook that contains just one play:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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  vars:
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    http_port: 80
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    max_clients: 200
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  user: root
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  tasks:
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  - name: ensure apache is at the latest version
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    action: yum pkg=httpd state=latest
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  - name: write the apache config file
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    action: template src=/srv/httpd.j2 dest=/etc/httpd.conf
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    notify:
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    - restart apache
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  - name: ensure apache is running
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    action: service name=httpd state=started
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  handlers:
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    - name: restart apache
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      action: service name=apache state=restarted</pre>
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</div>
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<p>Below, we’ll break down what the various features of the playbook language are.</p>
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</div>
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<div class="section" id="basics">
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<h2>Basics<a class="headerlink" href="#basics" title="Permalink to this headline">¶</a></h2>
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<div class="section" id="hosts-and-users">
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<h3>Hosts and Users<a class="headerlink" href="#hosts-and-users" title="Permalink to this headline">¶</a></h3>
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<p>For each play in a playbook, you get to choose which machines in your infrastructure
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to target and what remote user to complete the steps (called tasks) as.</p>
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<p>The <cite>hosts</cite> line is a list of one or more groups or host patterns,
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separated by colons, as described in the <a class="reference internal" href="patterns.html#patterns"><em>Inventory & Patterns</em></a>
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documentation.  The <cite>user</cite> is just the name of the user account:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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  user: root</pre>
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</div>
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<p>Support for running things from sudo is also available:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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  user: yourname
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  sudo: True</pre>
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</div>
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<p>You can also login as you, and then sudo to different users than root:</p>
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<div class="highlight-python"><pre>---
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- hosts: webservers
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  user: yourname
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  sudo: True
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  sudo_user: postgres</pre>
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</div>
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<p>If you need to specify a password to sudo, run <cite>ansible-playbook</cite> with <tt class="docutils literal"><span class="pre">--ask-sudo-pass</span></tt> (<cite>-K</cite>).
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If you run a sudo playbook and the playbook seems to hang, it’s probably stuck at the sudo prompt.
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Just <cite>Control-C</cite> to kill it and run it again with <cite>-K</cite>.</p>
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<div class="admonition important">
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<p class="first admonition-title">Important</p>
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<p class="last">When using <cite>sudo_user</cite> to a user other than root, the module
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arguments are briefly written into a random tempfile in /tmp.
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These are deleted immediately after the command is executed.  This
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only occurs when sudoing from a user like ‘bob’ to ‘timmy’, not
 | 
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when going from ‘bob’ to ‘root’, or logging in directly as ‘bob’ or
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‘root’.  If this concerns you that this data is briefly readable
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						|
(not writeable), avoid transferring uncrypted passwords with
 | 
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<cite>sudo_user</cite> set.  In other cases, ‘/tmp’ is not used and this does
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not come into play. Ansible also takes care to not log password
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parameters.</p>
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</div>
 | 
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</div>
 | 
						|
<div class="section" id="vars-section">
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<h3>Vars section<a class="headerlink" href="#vars-section" title="Permalink to this headline">¶</a></h3>
 | 
						|
<p>The <cite>vars</cite> section contains a list of variables and values that can be used in the plays, like this:</p>
 | 
						|
<div class="highlight-python"><pre>---
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- hosts: webservers
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  users: root
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  vars:
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     http_port: 80
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     van_halen_port: 5150
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     other: 'magic'</pre>
 | 
						|
</div>
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						|
<p>These variables can be used later in the playbook like this:</p>
 | 
						|
<div class="highlight-python"><pre>$varname or ${varname}</pre>
 | 
						|
</div>
 | 
						|
<p>The later is useful in the event you need to do something like ${other}_some_string.</p>
 | 
						|
<p>The full power of the <a class="reference external" href="http://jinja.pocoo.org/docs/">Jinja2</a> templating language is also available, which looks like this:</p>
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						|
<div class="highlight-python"><pre>{{ varname }}</pre>
 | 
						|
</div>
 | 
						|
<p>The Jinja2 documentation provides information about how to construct loops and conditionals for those
 | 
						|
who which to use more advanced templating.  This is optional and the $varname format still works in template
 | 
						|
files.</p>
 | 
						|
<p>If there are discovered variables about the system, called ‘facts’, these variables bubble up back into the
 | 
						|
playbook, and can be used on each system just like explicitly set variables.  Ansible provides several
 | 
						|
of these, prefixed with ‘ansible’, and are documented under <a class="reference internal" href="modules.html#setup"><em>setup</em></a> in the module documentation.  Additionally,
 | 
						|
facts can be gathered by ohai and facter if they are installed.  Facter variables are prefixed with <tt class="docutils literal"><span class="pre">facter_</span></tt> and Ohai
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						|
variables are prefixed with <tt class="docutils literal"><span class="pre">ohai_</span></tt>.</p>
 | 
						|
<p>So for instance, if I wanted
 | 
						|
to write the hostname into the /etc/motd file, I could say:</p>
 | 
						|
<div class="highlight-python"><pre>- name: write the motd
 | 
						|
  action: template src=/srv/templates/motd.j2 dest=/etc/motd</pre>
 | 
						|
</div>
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						|
<p>And in /srv/templates/motd.j2:</p>
 | 
						|
<div class="highlight-python"><pre>You are logged into {{ facter_hostname }}</pre>
 | 
						|
</div>
 | 
						|
<p>But we’re getting ahead of ourselves.  Let’s talk about tasks.</p>
 | 
						|
</div>
 | 
						|
<div class="section" id="tasks-list">
 | 
						|
<h3>Tasks list<a class="headerlink" href="#tasks-list" title="Permalink to this headline">¶</a></h3>
 | 
						|
<p>Each play contains a list of tasks.  Tasks are executed in order, one
 | 
						|
at a time, against all machines matched by the host pattern,
 | 
						|
before moving on to the next task.  It is important to understand that, within a play,
 | 
						|
all hosts are going to get the same task directives.  It is the purpose of a play to map
 | 
						|
a selection of hosts to tasks.</p>
 | 
						|
<p>When running the playbook, which runs top to bottom, hosts with failed tasks are
 | 
						|
taken out of the rotation for the entire playbook.  If things fail, simply correct the playbook file and rerun.</p>
 | 
						|
<p>The goal of each task is to execute a module, with very specific arguments.
 | 
						|
Variables, as mentioned above, can be used in arguments to modules.</p>
 | 
						|
<p>Modules are ‘idempotent’, meaning if you run them
 | 
						|
again, they will make the changes they are told to make to bring the
 | 
						|
system to the desired state.  This makes it very safe to rerun
 | 
						|
the same playbook multiple times.  They won’t change things
 | 
						|
unless they have to change things.</p>
 | 
						|
<p>The <cite>command</cite> and <cite>shell</cite> modules will typically rerun the same command again,
 | 
						|
which is totally ok if the command is something like
 | 
						|
‘chmod’ or ‘setsebool’, etc.  Though there is a ‘creates’ flag available which can
 | 
						|
be used to make these modules also idempotent.</p>
 | 
						|
<p>Every task should have a <cite>name</cite>, which is included in the output from
 | 
						|
running the playbook.   This is output for humans, so it is
 | 
						|
nice to have reasonably good descriptions of each task step.  If the name
 | 
						|
is not provided though, the string fed to ‘action’ will be used for
 | 
						|
output.</p>
 | 
						|
<p>Here is what a basic task looks like, as with most modules,
 | 
						|
the service module takes key=value arguments:</p>
 | 
						|
<div class="highlight-python"><pre>tasks:
 | 
						|
  - name: make sure apache is running
 | 
						|
    action: service name=httpd state=running</pre>
 | 
						|
</div>
 | 
						|
<p>The <cite>command</cite> and <cite>shell</cite> modules are the one modules that just takes a list
 | 
						|
of arguments, and don’t use the key=value form.  This makes
 | 
						|
them work just like you would expect. Simple:</p>
 | 
						|
<div class="highlight-python"><pre>tasks:
 | 
						|
  - name: disable selinux
 | 
						|
    action: command /sbin/setenforce 0</pre>
 | 
						|
</div>
 | 
						|
<p>The command and shell module care about return codes, so if you have a command
 | 
						|
who’s successful exit code is not zero, you may wish to do this:</p>
 | 
						|
<blockquote>
 | 
						|
<div><dl class="docutils">
 | 
						|
<dt>tasks:</dt>
 | 
						|
<dd><ul class="first last simple">
 | 
						|
<li>name: run this command and ignore the result
 | 
						|
action: shell /usr/bin/somecommand & /bin/true</li>
 | 
						|
</ul>
 | 
						|
</dd>
 | 
						|
</dl>
 | 
						|
</div></blockquote>
 | 
						|
<p>Variables can be used in action lines.   Suppose you defined
 | 
						|
a variable called ‘vhost’ in the ‘vars’ section, you could do this:</p>
 | 
						|
<div class="highlight-python"><pre>tasks:
 | 
						|
  - name: create a virtual host file for $vhost
 | 
						|
    action: template src=somefile.j2 dest=/etc/httpd/conf.d/$vhost</pre>
 | 
						|
</div>
 | 
						|
<p>Those same variables are usable in templates, which we’ll get to later.</p>
 | 
						|
<p>Now in a very basic playbook all the tasks will be listed directly in that play, though it will usually
 | 
						|
make more sense to break up tasks using the ‘include:’ directive.  We’ll show that a bit later.</p>
 | 
						|
</div>
 | 
						|
</div>
 | 
						|
<div class="section" id="running-operations-on-change">
 | 
						|
<h2>Running Operations On Change<a class="headerlink" href="#running-operations-on-change" title="Permalink to this headline">¶</a></h2>
 | 
						|
<p>As we’ve mentioned, modules are written to be ‘idempotent’ and can relay  when
 | 
						|
they have made a change on the remote system.   Playbooks recognize this and
 | 
						|
have a basic event system that can be used to respond to change.</p>
 | 
						|
<p>These ‘notify’ actions are triggered at the end of each ‘play’ in a playbook, and
 | 
						|
trigger only once each.  For instance, multiple resources may indicate
 | 
						|
that apache needs to be restarted, but apache will only be bounced once.</p>
 | 
						|
<p>Here’s an example of restarting two services when the contents of a file
 | 
						|
change, but only if the file changes:</p>
 | 
						|
<div class="highlight-python"><pre>- name: template configuration file
 | 
						|
  action: template src=template.j2 dest=/etc/foo.conf
 | 
						|
  notify:
 | 
						|
     - restart memcached
 | 
						|
     - restart apache</pre>
 | 
						|
</div>
 | 
						|
<p>The things listed in the ‘notify’ section of a task are called
 | 
						|
handlers.</p>
 | 
						|
<p>Handlers are lists of tasks, not really any different from regular
 | 
						|
tasks, that are referenced by name.  Handlers are what notifiers
 | 
						|
notify.  If nothing notifies a handler, it will not run.  Regardless
 | 
						|
of how many things notify a handler, it will run only once, after all
 | 
						|
of the tasks complete in a particular play.</p>
 | 
						|
<p>Here’s an example handlers section:</p>
 | 
						|
<div class="highlight-python"><pre>handlers:
 | 
						|
    - name: restart memcached
 | 
						|
      action: service name=memcached state=restarted
 | 
						|
    - name: restart apache
 | 
						|
      action: service name=apache state=restarted</pre>
 | 
						|
</div>
 | 
						|
<p>Handlers are best used to restart services and trigger reboots.  You probably
 | 
						|
won’t need them for much else.</p>
 | 
						|
<div class="admonition note">
 | 
						|
<p class="first admonition-title">Note</p>
 | 
						|
<p class="last">Notify handlers are always run in the order written.</p>
 | 
						|
</div>
 | 
						|
</div>
 | 
						|
<div class="section" id="include-files-and-encouraging-reuse">
 | 
						|
<h2>Include Files And Encouraging Reuse<a class="headerlink" href="#include-files-and-encouraging-reuse" title="Permalink to this headline">¶</a></h2>
 | 
						|
<p>Suppose you want to reuse lists of tasks between plays or playbooks.  You can use
 | 
						|
include files to do this.  Use of included task lists is a great way to define a role
 | 
						|
that system is going to fulfill.  Remember, the goal of a play in a playbook is to map
 | 
						|
a group of systems into multiple roles.  Let’s see what this looks like...</p>
 | 
						|
<p>A task include file simply contains a flat list of tasks, like so:</p>
 | 
						|
<div class="highlight-python"><pre>---
 | 
						|
# possibly saved as tasks/foo.yml
 | 
						|
- name: placeholder foo
 | 
						|
  action: command /bin/foo
 | 
						|
- name: placeholder bar
 | 
						|
  action: command /bin/bar</pre>
 | 
						|
</div>
 | 
						|
<p>Include directives look like this, and can be mixed in with regular tasks in a playbook:</p>
 | 
						|
<div class="highlight-python"><pre>tasks:
 | 
						|
 - include: tasks/foo.yml</pre>
 | 
						|
</div>
 | 
						|
<p>You can also pass variables into includes.  We call this a ‘parameterized include’.</p>
 | 
						|
<p>For instance, if deploying multiple wordpress instances, I could
 | 
						|
contain all of my wordpress tasks in a single wordpress.yml file, and use it like so:</p>
 | 
						|
<div class="highlight-python"><pre>tasks:
 | 
						|
  - include: wordpress.yml user=timmy
 | 
						|
  - include: wordpress.yml user=alice
 | 
						|
  - include: wordpress.yml user=bob</pre>
 | 
						|
</div>
 | 
						|
<p>Variables passed in can then be used in the included files.  You can reference them like this:</p>
 | 
						|
<div class="highlight-python"><pre>$user</pre>
 | 
						|
</div>
 | 
						|
<p>(In addition to the explicitly passed in parameters, all variables from
 | 
						|
the vars section are also available for use here as well.)</p>
 | 
						|
<div class="admonition note">
 | 
						|
<p class="first admonition-title">Note</p>
 | 
						|
<p class="last">Task include statements are only usable one-level deep.
 | 
						|
This means task includes can not include other
 | 
						|
task includes.  This may change in a later release.</p>
 | 
						|
</div>
 | 
						|
<p>Includes can also be used in the ‘handlers’ section, for instance, if you
 | 
						|
want to define how to restart apache, you only have to do that once for all
 | 
						|
of your playbooks.  You might make a handlers.yml that looks like:</p>
 | 
						|
<div class="highlight-python"><pre>----
 | 
						|
# this might be in a file like handlers/handlers.yml
 | 
						|
- name: restart apache
 | 
						|
  action: service name=apache state=restarted</pre>
 | 
						|
</div>
 | 
						|
<p>And in your main playbook file, just include it like so, at the bottom
 | 
						|
of a play:</p>
 | 
						|
<div class="highlight-python"><pre>handlers:
 | 
						|
  - include: handlers/handlers.yml</pre>
 | 
						|
</div>
 | 
						|
<p>You can mix in includes along with your regular non-included tasks and handlers.</p>
 | 
						|
<div class="admonition note">
 | 
						|
<p class="first admonition-title">Note</p>
 | 
						|
<p class="last">You can not conditionally path the location to an include file,
 | 
						|
like you can with ‘vars_files’.  If you find yourself needing to do
 | 
						|
this, consider how you can restructure your playbook to be more
 | 
						|
class/role oriented.  This is to say you cannot use a ‘fact’ to
 | 
						|
decide what include file to use.  All hosts contained within the
 | 
						|
play are going to get the same tasks.  (‘only_if’ provides some
 | 
						|
ability for hosts to conditionally skip tasks).</p>
 | 
						|
</div>
 | 
						|
</div>
 | 
						|
<div class="section" id="executing-a-playbook">
 | 
						|
<h2>Executing A Playbook<a class="headerlink" href="#executing-a-playbook" title="Permalink to this headline">¶</a></h2>
 | 
						|
<p>Now that you’ve learned playbook syntax, how do you run a playbook?  It’s simple.
 | 
						|
Let’s run a playbook using a parallelism level of 10:</p>
 | 
						|
<div class="highlight-python"><pre>ansible-playbook playbook.yml -f 10</pre>
 | 
						|
</div>
 | 
						|
</div>
 | 
						|
<div class="section" id="tips-and-tricks">
 | 
						|
<h2>Tips and Tricks<a class="headerlink" href="#tips-and-tricks" title="Permalink to this headline">¶</a></h2>
 | 
						|
<p>Look at the bottom of the playbook execution for a summary of the nodes that were executed
 | 
						|
and how they performed.   General failures and fatal “unreachable” communication attempts are
 | 
						|
kept seperate in the counts.</p>
 | 
						|
<p>If you ever want to see detailed output from successful modules as well as unsuccessful ones,
 | 
						|
use the ‘–verbose’ flag.  This is available in Ansible 0.5 and later.</p>
 | 
						|
<p>Also, in version 0.5 and later, Ansible playbook output is vastly upgraded if the cowsay
 | 
						|
package is installed.  Try it!</p>
 | 
						|
<div class="admonition-see-also admonition seealso">
 | 
						|
<p class="first admonition-title">See also</p>
 | 
						|
<dl class="last docutils">
 | 
						|
<dt><a class="reference internal" href="YAMLSyntax.html"><em>YAML Syntax</em></a></dt>
 | 
						|
<dd>Learn about YAML syntax</dd>
 | 
						|
<dt><a class="reference internal" href=""><em>Playbooks</em></a></dt>
 | 
						|
<dd>Review the basic Playbook language features</dd>
 | 
						|
<dt><a class="reference internal" href="playbooks2.html"><em>Advanced Playbooks</em></a></dt>
 | 
						|
<dd>Learn about Advanced Playbook Features</dd>
 | 
						|
<dt><a class="reference internal" href="bestpractices.html"><em>Best Practices</em></a></dt>
 | 
						|
<dd>Various tips about managing playbooks in the real world</dd>
 | 
						|
<dt><a class="reference internal" href="modules.html"><em>Ansible Modules</em></a></dt>
 | 
						|
<dd>Learn about available modules</dd>
 | 
						|
<dt><a class="reference internal" href="moduledev.html"><em>Module Development</em></a></dt>
 | 
						|
<dd>Learn how to extend Ansible by writing your own modules</dd>
 | 
						|
<dt><a class="reference internal" href="patterns.html"><em>Inventory & Patterns</em></a></dt>
 | 
						|
<dd>Learn about how to select hosts</dd>
 | 
						|
<dt><a class="reference external" href="https://github.com/ansible/ansible/tree/devel/examples/playbooks">Github examples directory</a></dt>
 | 
						|
<dd>Complete playbook files from the github project source</dd>
 | 
						|
<dt><a class="reference external" href="http://groups.google.com/group/ansible-project">Mailing List</a></dt>
 | 
						|
<dd>Questions? Help? Ideas?  Stop by the list on Google Groups</dd>
 | 
						|
</dl>
 | 
						|
</div>
 | 
						|
</div>
 | 
						|
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        © Copyright 2012 Michael DeHaan.<br/>
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      Last updated on Aug 09, 2012.<br/>
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