=======================
About OpenStack-Ansible
=======================

OpenStack-Ansible (OSA) uses the `Ansible <https://www.ansible.com/how-ansible-works>`_
IT automation engine to deploy an OpenStack environment on Ubuntu Linux.
For isolation and ease of maintenance, you can install OpenStack components
into Linux containers (LXC).

Ansible
~~~~~~~

Ansible provides an automation platform to simplify system and application
deployment. Ansible manages systems by using Secure Shell (SSH)
instead of unique protocols that require remote daemons or agents.

Ansible uses playbooks written in the YAML language for orchestration.
For more information, see `Ansible - Intro to
Playbooks <http://docs.ansible.com/playbooks_intro.html>`_.

This guide refers to the following types of hosts:

* `Deployment host`, which runs the Ansible playbooks
* `Target hosts`, where Ansible installs OpenStack services and infrastructure
  components

Linux containers (LXC)
~~~~~~~~~~~~~~~~~~~~~~

Containers provide operating-system level virtualization by enhancing
the concept of ``chroot`` environments. Containers isolate resources and file
systems for a particular group of processes without the overhead and
complexity of virtual machines. They access the same kernel, devices,
and file systems on the underlying host and provide a thin operational
layer built around a set of rules.

The LXC project implements operating-system-level
virtualization on Linux by using kernel namespaces, and it includes the
following features:

* Resource isolation including CPU, memory, block I/O, and network, by
  using ``cgroups``
* Selective connectivity to physical and virtual network devices on the
  underlying physical host
* Support for a variety of backing stores, including Logical Volume Manager
  (LVM)
* Built on a foundation of stable Linux technologies with an active
  development and support community

Installation workflow
~~~~~~~~~~~~~~~~~~~~~

The following diagram shows the general workflow of an OpenStack-Ansible
installation.

.. figure:: figures/installation-workflow-overview.png
   :width: 100%

#. :ref:`deployment-host`
#. :ref:`target-hosts`
#. :ref:`configure`
#. :ref:`run-playbooks`
#. :ref:`verify-operation`