salt/doc/topics/tutorials/starting_states.rst

=========================
How Do I Use Salt States?
=========================

Simplicity, Simplicity, Simplicity

Many of the most powerful and useful engineering solutions are founded on
simple principles. The Salt SLS system strives to do just that. K.I.S.S. 
(Keep It Stupidly Simple)

The core of the Salt State system is the SLS, or the SaLt State file. The SLS
is a representation of the state in which a system should be in, and is set up
to contain this data in a simple format. This is often called configuration 
management.

.. note::

    This is just the beginning of using states, make sure to read up on pillar
    :doc:`Pillar </topics/tutorials/pillar>` next.


It is All Just Data
===================

Before delving into the particulars, it will help to understand that the SLS 
file is just a data structure under the hood. While understanding that the SLS 
is just a data structure isn't critical for understanding and making use of 
Salt States, it should help bolster knowledge of where the real power is.

SLS files are therefore, in reality, just `dictionaries`_, `lists`_,
`strings`_, and `numbers`_. By using this approach Salt can be much more
flexible. As one writes more state files, it becomes clearer exactly what is
being written. The result is a system that is easy to understand, yet grows
with the needs of the admin or developer.

In the section titled "State Data Structures" a reference exists, explaining
in depth how the data is laid out.

.. _`dictionaries`: http://docs.python.org/glossary.html#term-dictionary
.. _`lists`: http://docs.python.org/glossary.html#term-list
.. _`strings`: http://docs.python.org/library/stdtypes.html#typesseq
.. _`numbers`: http://docs.python.org/library/stdtypes.html#numeric-types-int-float-long-complex


Default Data - YAML
===================

By default Salt represents the SLS data in what is one of the simplest
serialization formats available - `YAML`_.

A typical SLS file will often look like this in YAML:

.. note::

    These demos use some generic service and package names, different
    distributions often use different names for packages and services. For
    instance `apache` should be replaced with `httpd` on a Red Hat system.
    Salt uses the name of the init script, systemd name, upstart name etc.
    based on what the underlying service management for the platform. To
    get a list of the available service names on a platform execute the
    service.get_all salt function.

    Information on how to make states work with multiple distributions
    is later in the tutorial.

.. code-block:: yaml
   :linenos:

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

This SLS data will ensure that the package named apache is installed, and
that the apache service is running. The components can be explained in a
simple way.

The first line is the ID for a set of data, and it is called the ID
Declaration. This ID sets the name of the thing that needs to be manipulated.

The second and fourth lines are the start of the State Declarations, so they
are using the pkg and service states respectively. The pkg state manages a
software package to be installed via the system's native package manager,
and the service state manages a system daemon. 

The third and fifth lines are the function to run. This function defines what 
state the named package and service should be in. Here, the package is to be 
installed, and the service should be running.

Finally, on line six, is the word ``require``. This is called a Requisite
Statement, and it makes sure that the Apache service is only started after
a successful installation of the apache package.

.. _`YAML`: http://yaml.org/spec/1.1/


Adding Configs and Users
========================

When setting up a service like an Apache web server, many more components may
need to be added. The Apache configuration file will most likely be managed,
and a user and group may need to be set up.

.. code-block:: yaml
   :linenos:

    apache:
      pkg:
        - installed
      service:
        - running
        - watch:
          - pkg: apache
          - file: /etc/httpd/conf/httpd.conf
          - user: apache
      user.present:
        - uid: 87
        - gid: 87
        - home: /var/www/html
        - shell: /bin/nologin
        - require:
          - group: apache
      group.present:
        - gid: 87
        - require:
          - pkg: apache

    /etc/httpd/conf/httpd.conf:
      file.managed:
        - source: salt://apache/httpd.conf
        - user: root
        - group: root
        - mode: 644

This SLS data greatly extends the first example, and includes a config file,
a user, a group and new requisite statement: ``watch``.

Adding more states is easy, since the new user and group states are under
the Apache ID, the user and group will be the Apache user and group. The
``require`` statements will make sure that the user will only be made after
the group, and that the group will be made only after the Apache package is
installed.

Next,the ``require`` statement under service was changed to watch, and is
now watching 3 states instead of just one. The watch statement does the same
thing as require, making sure that the other states run before running the
state with a watch, but it adds an extra component. The ``watch`` statement
will run the state's watcher function for any changes to the watched states. 
So if the package was updated, the config file changed, or the user
uid modified, then the service state's watcher will be run. The service
state's watcher just restarts the service, so in this case, a change in the
config file will also trigger a restart of the respective service.


Moving Beyond a Single SLS
==========================

When setting up Salt States in a scalable manner, more than one SLS will need 
to be used. The above examples were in a single SLS file, but two or more 
SLS files can be combined to build out a State Tree. The above example also 
references a file with a strange source - ``salt://apache/httpd.conf``. That 
file will need to be available as well.

The SLS files are laid out in a directory structure on the Salt master; an 
SLS is just a file and files to download are just files.

The Apache example would be laid out in the root of the Salt file server like
this: ::

    apache/init.sls
    apache/httpd.conf

So the httpd.conf is just a file in the apache directory, and is referenced
directly.

But when using more than one single SLS file, more components can be added to 
the toolkit. Consider this SSH example:

``ssh/init.sls:``

.. code-block:: yaml
   :linenos:

    openssh-client:
      pkg.installed

    /etc/ssh/ssh_config:
      file.managed:
        - user: root
        - group: root
        - mode: 644
        - source: salt://ssh/ssh_config
        - require:
          - pkg: openssh-client

``ssh/server.sls:``

.. code-block:: yaml
   :linenos:

    include:
      - ssh

    openssh-server:
      pkg.installed

    sshd:
      service.running:
        - require:
          - pkg: openssh-client
          - pkg: openssh-server
          - file: /etc/ssh/banner
          - file: /etc/ssh/sshd_config

    /etc/ssh/sshd_config:
      file.managed:
        - user: root
        - group: root
        - mode: 644
        - source: salt://ssh/sshd_config
        - require:
          - pkg: openssh-server

    /etc/ssh/banner:
      file:
        - managed
        - user: root
        - group: root
        - mode: 644
        - source: salt://ssh/banner
        - require:
          - pkg: openssh-server

.. note:: 

    Notice that we use two similar ways of denoting that a file
    is managed by Salt. In the `/etc/ssh/sshd_config` state section above,
    we use the `file.managed` state declaration whereas with the
    `/etc/ssh/banner` state section, we use the `file` state declaration
    and add a `managed` attribute to that state declaration. Both ways
    produce an identical result; the first way -- using `file.managed` --
    is merely a shortcut.

Now our State Tree looks like this: ::

    apache/init.sls
    apache/httpd.conf
    ssh/init.sls
    ssh/server.sls
    ssh/banner
    ssh/ssh_config
    ssh/sshd_config

This example now introduces the ``include`` statement. The include statement
includes another SLS file so that components found in it can be required,
watched or as will soon be demonstrated - extended.

The include statement allows for states to be cross linked. When an SLS
has an include statement it is literally extended to include the contents of
the included SLS files.

Note that some of the SLS files are called init.sls, while others are not. More
info on what this means can be found in the :ref:`States Tutorial
<sls-file-namespace>`.


Extending Included SLS Data
===========================

Sometimes SLS data needs to be extended. Perhaps the apache service needs to
watch additional resources, or under certain circumstances a different file
needs to be placed.

In these examples, the first will add a custom banner to ssh and the second will 
add more watchers to apache to include mod_python.

``ssh/custom-server.sls:``

.. code-block:: yaml
   :linenos:

    include:
      - ssh.server

    extend:
      /etc/ssh/banner:
        file:
          - source: salt://ssh/custom-banner

``python/mod_python.sls:``

.. code-block:: yaml
   :linenos:

    include:
      - apache

    extend:
      apache:
        service:
          - watch:
            - pkg: mod_python

    mod_python:
      pkg.installed

The ``custom-server.sls`` file uses the extend statement to overwrite where the
banner is being downloaded from, and therefore changing what file is being used
to configure the banner.

In the new mod_python SLS the mod_python package is added, but more importantly
the apache service was extended to also watch the mod_python package.

.. include:: /_incl/extend_with_require_watch.rst


Understanding the Render System
===============================

Since SLS data is simply that (data), it does not need to be represented
with YAML. Salt defaults to YAML because it is very straightforward and easy
to learn and use. But the SLS files can be rendered from almost any imaginable
medium, so long as a renderer module is provided.

The default rendering system is the ``yaml_jinja`` renderer. The
``yaml_jinja`` renderer will first pass the template through the `Jinja2`_
templating system, and then through the YAML parser. The benefit here is that
full programming constructs are available when creating SLS files.

Other renderers available are ``yaml_mako`` and ``yaml_wempy`` which each use
the `Mako`_ or `Wempy`_ templating system respectively rather than the jinja
templating system, and more notably, the pure Python or ``py`` and ``pydsl``
renderers.
The ``py`` renderer allows for SLS files to be written in pure Python, 
allowing for the utmost level of flexibility and power when preparing SLS 
data; while the :doc:`pydsl</ref/renderers/all/salt.renderers.pydsl>` renderer 
provides a flexible, domain-specific language for authoring SLS data in Python.

.. _`Jinja2`: http://jinja.pocoo.org/
.. _`Mako`: http://www.makotemplates.org/
.. _`Wempy`: http://www.wempy.org/

.. note::
    The templating engines described above aren't just available in SLS files.
    They can also be used in :mod:`file.managed <salt.states.file.managed>`
    states, making file management much more dynamic and flexible. Some
    examples for using templates in managed files can be found in the
    documentation for the :doc:`file states
    </ref/states/all/salt.states.file>`, as well as the :ref:`MooseFS
    example<jinja-example-moosefs>` below.


Getting to Know the Default - yaml_jinja
----------------------------------------

The default renderer - ``yaml_jinja``, allows for use of the jinja
templating system. A guide to the Jinja templating system can be found here:
http://jinja.pocoo.org/docs

When working with renderers a few very useful bits of data are passed in. In
the case of templating engine based renderers, three critical components are
available, ``salt``, ``grains``, and ``pillar``. The ``salt`` object allows for
any Salt function to be called from within the template, and ``grains`` allows 
for the Grains to be accessed from within the template. A few examples:

``apache/init.sls:``

.. code-block:: yaml
   :linenos:

    apache:
      pkg.installed:
        {% if grains['os'] == 'RedHat'%}
        - name: httpd
        {% endif %}
      service.running:
        {% if grains['os'] == 'RedHat'%}
        - name: httpd
        {% endif %}
        - watch:
          - pkg: apache
          - file: /etc/httpd/conf/httpd.conf
          - user: apache
      user.present:
        - uid: 87
        - gid: 87
        - home: /var/www/html
        - shell: /bin/nologin
        - require:
          - group: apache
      group.present:
        - gid: 87
        - require:
          - pkg: apache

    /etc/httpd/conf/httpd.conf:
      file.managed:
        - source: salt://apache/httpd.conf
        - user: root
        - group: root
        - mode: 644

This example is simple. If the ``os`` grain states that the operating system is
Red Hat, then the name of the Apache package and service needs to be httpd.

.. _jinja-example-moosefs:

A more aggressive way to use Jinja can be found here, in a module to set up
a MooseFS distributed filesystem chunkserver:

``moosefs/chunk.sls:``

.. code-block:: yaml
   :linenos:

    include:
      - moosefs

    {% for mnt in salt['cmd.run']('ls /dev/data/moose*').split() %}
    /mnt/moose{{ mnt[-1] }}:
      mount.mounted:
        - device: {{ mnt }}
        - fstype: xfs
        - mkmnt: True
      file.directory:
        - user: mfs
        - group: mfs
        - require:
          - user: mfs
          - group: mfs
    {% endfor %}

    /etc/mfshdd.cfg:
      file.managed:
        - source: salt://moosefs/mfshdd.cfg
        - user: root
        - group: root
        - mode: 644
        - template: jinja
        - require:
          - pkg: mfs-chunkserver

    /etc/mfschunkserver.cfg:
      file.managed:
        - source: salt://moosefs/mfschunkserver.cfg
        - user: root
        - group: root
        - mode: 644
        - template: jinja
        - require:
          - pkg: mfs-chunkserver

    mfs-chunkserver:
      pkg:
        - installed
    mfschunkserver:
      service:
        - running
        - require:
    {% for mnt in salt['cmd.run']('ls /dev/data/moose*') %}
          - mount: /mnt/moose{{ mnt[-1] }}
          - file: /mnt/moose{{ mnt[-1] }}
    {% endfor %}
          - file: /etc/mfschunkserver.cfg
          - file: /etc/mfshdd.cfg
          - file: /var/lib/mfs

This example shows much more of the available power of Jinja.
Multiple for loops are used to dynamically detect available hard drives
and set them up to be mounted, and the ``salt`` object is used multiple
times to call shell commands to gather data.


Introducing the Python and the PyDSL Renderers
----------------------------------------------

Sometimes the chosen default renderer might not have enough logical power to
accomplish the needed task. When this happens, the Python renderer can be
used. Normally a YAML renderer should be used for the majority of SLS files,
but an SLS file set to use another renderer can be easily added to the tree.

This example shows a very basic Python SLS file:

``python/django.sls:``

.. code-block:: python
   :linenos:

    #!py

    def run():
        '''
        Install the django package
        '''
        return {'include': ['python'],
                'django': {'pkg': ['installed']}}

This is a very simple example; the first line has an SLS shebang that
tells Salt to not use the default renderer, but to use the ``py`` renderer.
Then the run function is defined, the return value from the run function
must be a Salt friendly data structure, or better known as a Salt
:doc:`HighState data structure</ref/states/highstate>`.

Alternatively, using the :doc:`pydsl</ref/renderers/all/salt.renderers.pydsl>`
renderer, the above example can be written more succinctly as:

``python/django.sls:``

.. code-block:: python
   :linenos:

    #!pydsl

    include('python', delayed=True)
    state('django').pkg.installed()


This Python examples would look like this if they were written in YAML:

.. code-block:: yaml
   :linenos:

    include:
      - python

    django:
      pkg.installed

This example clearly illustrates that; one, using the YAML renderer by default 
is a wise decision and two, unbridled power can be obtained where needed by 
using a pure Python SLS.

Running and debugging salt states.
----------------------------------

Once the rules in an SLS are ready, they should be tested to ensure they
work properly. To invoke these rules, simply execute 
``salt '*' state.highstate`` on the command line. If you get back only 
hostnames with a `':'` after, but no return, chances are there is a problem with 
one or more of the sls files. On the minion, use the ``salt-call`` command: 
``salt-call state.highstate -l debug`` to examine the output for errors. 
This should help troubleshoot the issue. The minions can also be started in 
the foreground in debug mode: ``salt-minion -l debug``.

Next Reading
============

With an understanding of states, the next recommendation is to become familiar
with Salt's pillar interface:

    :doc:`Pillar Walkthrough </topics/tutorials/pillar>`