Configure Ansible
"""""""""""""""""

Configure Ansible Core
======================
* one configuration file
* nearly all parameters can be overridden in ``ansible-playbook`` or with command line flags
* there are several places for configuration files, the first matches

    #. set the variable ``ANSIBLE_CONFIG`` for your config path
    #. place a ``ansible.cfg`` configuration file in the working directory
    #. place a ``.ansible.cfg`` configuration file in your home directory
    #. ``/etc/ansible/ansible.cfg``

A short example of a configuration file.

.. code-block:: bash

    [defaults]
    inventory = hosts

    [privilege_escalation]
    become = True
    become_method = sudo
    become_user = root

.. hint::
    
    There are some advanced configuration sections to tune Ansible: **ssh_connection** and **accelerate**


Links
-----
* http://docs.ansible.com/ansible/intro_configuration.html
* `official Ansible config file <https://github.com/ansible/ansible/blob/stable-2.0/examples/ansible.cfg>`_
* `Ansible SSH Tuning <https://www.ansible.com/blog/ansible-performance-tuning>`_


Configure a static inventory
============================
* Inventory is the representation of information about hosts
* defines what groups a host belongs to
* a hierarchy of groups often results
* the inventory path can be set in the Ansible config file (``inventory =``)
* the static file is often named ``hosts``
* the entries can be fqdn or ip-addresses

.. code-block:: bash

    # static inventory file
    srv.pascal.lab
    web1.pascal.lab


Links
-----
* http://docs.ansible.com/ansible/intro_inventory.html
* http://docs.ansible.com/ansible/latest/intro_patterns.html


Host Groups
-----------
* the host group name is defined in brackets ``[myhostgroup]``
* systems can be in more than one group
* variables can be set for a group of hosts in ``group_vars``
* you can have groups of groups with ``children:``
* INI-like format of the file
* don't use dashes ``-`` in group names

.. code-block:: yaml

    [zurich]                      <- group name zurich
    web1.lab                      <- host in the group zurich
    db1.lab

    [berne]
    web2.lab
    db2.lab

    [switzerland:children]        <- group name switzerland
    zurich                        <- sub-group in the group switzerland
    berne

Inventory Patterns
------------------
* you can also define ranges for numbers or letters

.. code-block:: yaml

    [web]
    web[01:25].lab

* intersections ``webservers:&staging``


Links
-----
* http://docs.ansible.com/ansible/intro_inventory.html#hosts-and-groups
* http://docs.ansible.com/ansible/latest/user_guide/intro_patterns.html