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Adding getting started guide for Docker

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Getting Started with Docker
===========================
Ansible offers the following modules for orchestrating Docker containers:
docker_container
Manages the container lifecycle by providing the ability to create, update, stop, start and destroy a
container.
docker_image
Provides full control over images, including: build, pull, push, tag and remove.
docker_image_facts
Inspects one or more images in the Docker host's image cache, providing the information as facts for making
decision or assertions in a playbook.
docker_login
Authenticates with Docker Hub or any Docker registry and updates the Docker Engine config file, which
in turn provides password-free pushing and pulling of images to and from the registry.
docker (dynamic inventory)
Dynamically builds an inventory of all the available containers from a set of one or more Docker hosts.
Ansible 2.1.0 includes major updates to the Docker modules, marking the start of a project to create a complete and
integrated set of tools for orchestrating containers. The docker_image and docker_login modules as well as the dynamic
inventory script were refactored to use a common set of parameters and environment variables for shaping Docker API
connections. The docker_container and docker_image_facts modules are new.
Requirements
------------
Using the docker modules requires having `docker-py <https://docker-py.readthedocs.org/en/stable/>`_
installed on the host running Ansible. You will need to have >= 1.7.0 installed.
.. code-block:: bash
$ pip install docker-py>=1.7.0
Connecting to the Docker API
----------------------------
You can connect to a local or remote API using command line parameters passed to each task or by setting environment
variables. The order of precedence is command line parameters and then environment variables. If neither a command line
option for a environment variable is found, then a default value will be used. The default values are provided under
`Command Line Parameters`_
Command Line Parameters
.......................
Control how modules connect to the Docker API by passing the following options to a task:
docker_host
The URL or Unix socket path used to connect to the Docker API. Defaults to ``unix://var/run/docker.sock``.
To connect to a remote host, provide the TCP connection string. For example: ``tcp://192.168.99.100:2376``. If
TLS is used to encrypt the connection to the API, then 'tcp' in the connection URL will be replace with 'https'.
api_version
The version of the Docker API running on the Docker Host. Defaults to the latest version of the API supported
by docker-py.
timeout
The maximum amount of time in seconds to wait on a response from the API. Defaults to 60 seconds.
tls
Secure the connection to the API by using TLS without verifying the authenticity of the Docker host server.
Defaults to False.
tls_verify
Secure the connection to the API by using TLS and verifying the authenticity of the Docker host server.
Default is False.
cacert_path
Use a CA certificate when performing server verification by providing the path to a CA certificate file.
cert_path
Path to the client's TLS certificate file.
key_path
Path to the clients TLS key file.
tls_hostname
When verifying the authenticity of the Docker Host server, provide the expected name of the server. Defaults
to 'localhost'.
ssl_version
Provide a valid SSL version number. Default value determined by docker-py, which at the time of this writing
was 1.0
Environment Variables
.....................
Control how the modules connect to the Docker API by setting the following variables in the environment of the host
running Ansible:
DOCKER_HOST
The URL or Unix socket path used to connect to the Docker API.
DOCKER_API_VERSION
The version of the Docker API running on the Docker Host. Defaults to the latest version of the API supported
by docker-py.
DOCKER_TIMEOUT
The maximum amount of time in seconds to wait on a response from the API.
DOCKER_CERT_PATH
Path to the directory containing the client certificate, client key and CA certificate.
DOCKER_SSL_VERSION
Provide a valid SSL version number.
DOCKER_TLS
Secure the connection to the API by using TLS without verifying the authenticity of the Docker Host.
DOCKER_TLS_VERIFY
Secure the connection to the API by using TLS and verify the authenticity of the Docker Host.
Dynamic Inventory Script
------------------------
The inventory script generates dynamic inventory by making API requests to one or more Docker APIs. It's dynamic
because the inventory is generated at run-time rather than being read from a static file. The script generates the
inventory by connecting to one or many Docker APIs and inspecting the containers it finds at each API. Which APIs the
script contacts can be defined using environment variables or a configuration file.
Groups
......
The script will create the following host groups:
- container id
- container name
- container short id
- image_name (image_<image name>)
- docker_host
- running
- stopped
Examples
........
You can run the script interactively from the command line or pass it as the inventory to a playbook. Here are few
examples to get you started:
.. code-block:: bash
# Connect to the Docker API on localhost port 4243 and format the JSON output
DOCKER_HOST=tcp://localhost:4243 ./docker.py --pretty
# Any container's ssh port exposed on 0.0.0.0 will be mapped to
# another IP address (where Ansible will attempt to connect via SSH)
DOCKER_DEFAULT_IP=1.2.3.4 ./docker.py --pretty
# Run as input to a playbook:
ansible-playbook -i ~/projects/ansible/contrib/inventory/docker.py docker_inventory_test.yml
# Simple playbook to invoke with the above example:
- name: Test docker_inventory
hosts: all
connection: local
gather_facts: no
tasks:
- debug: msg="Container - {{ inventory_hostname }}"
Configuration
..............
You can control the behavior of the inventory script by defining environment variables, or
creating a docker.yml file (sample provided in ansible/contrib/inventory). The order of precedence is the docker.yml
file and then environment variables.
Environment Variables
;;;;;;;;;;;;;;;;;;;;;;
To connect to a single Docker API the following variables can be defined in the environment to control the connection
options. These are the same environment variables used by the Docker modules.
DOCKER_HOST
The URL or Unix socket path used to connect to the Docker API. Defaults to unix://var/run/docker.sock.
DOCKER_API_VERSION:
The version of the Docker API running on the Docker Host. Defaults to the latest version of the API supported
by docker-py.
DOCKER_TIMEOUT:
The maximum amount of time in seconds to wait on a response fromm the API. Defaults to 60 seconds.
DOCKER_TLS:
Secure the connection to the API by using TLS without verifying the authenticity of the Docker host server.
Defaults to False.
DOCKER_TLS_VERIFY:
Secure the connection to the API by using TLS and verifying the authenticity of the Docker host server.
Default is False
DOCKER_TLS_HOSTNAME:
When verifying the authenticity of the Docker Host server, provide the expected name of the server. Defaults
to localhost.
DOCKER_CERT_PATH:
Path to the directory containing the client certificate, client key and CA certificate.
DOCKER_SSL_VERSION:
Provide a valid SSL version number. Default value determined by docker-py, which at the time of this writing
was 1.0
In addition to the connection variables there are a couple variables used to control the execution and output of the
script:
DOCKER_CONFIG_FILE
Path to the configuration file. Defaults to ./docker.yml.
DOCKER_PRIVATE_SSH_PORT:
The private port (container port) on which SSH is listening for connections. Defaults to 22.
DOCKER_DEFAULT_IP:
The IP address to assign to ansible_host when the container's SSH port is mapped to interface '0.0.0.0'.
Configuration File
;;;;;;;;;;;;;;;;;;
Using a configuration file provides a means for defining a set of Docker APIs from which to build an inventory.
The default name of the file is derived from the name of the inventory script. By default the script will look for
basename of the script (i.e. docker) with an extension of '.yml'.
You can also override the default name of the script by defining DOCKER_CONFIG_FILE in the environment.
Here's what you can define in docker_inventory.yml:
* defaults: Defines a default connection. Defaults will be taken from this and applied to any values not provided
for a host defined in the hosts list.
* hosts: If you wish to get inventory from more than one Docker host, define a hosts list.
For the default host and each host in the hosts list define the following attributes:
.. code-block:: yaml
host:
description: The URL or Unix socket path used to connect to the Docker API.
required: yes
tls:
description: Connect using TLS without verifying the authenticity of the Docker host server.
default: false
required: false
tls_verify:
description: Connect using TLS without verifying the authenticity of the Docker host server.
default: false
required: false
cert_path:
description: Path to the client's TLS certificate file.
default: null
required: false
cacert_path:
description: Use a CA certificate when performing server verification by providing the path to a CA certificate file.
default: null
required: false
key_path:
description: Path to the client's TLS key file.
default: null
required: false
version:
description: The Docker API version.
required: false
default: will be supplied by the docker-py module.
timeout:
description: The amount of time in seconds to wait on an API response.
required: false
default: 60
default_ip:
description: The IP address to assign to ansible_host when the container's SSH port is mapped to interface
'0.0.0.0'.
required: false
default: 127.0.0.1
private_ssh_port:
description: The port containers use for SSH
required: false
default: 22

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Detailed Guides
```````````````
This section is new and evolving. The idea here is explore particular use cases in greater depth and provide a more "top down" explanation of some basic features.
This section is new and evolving. The idea here is to explore particular use cases in greater depth and provide a more "top down" explanation of some basic features.
.. toctree::
:maxdepth: 1
@ -13,5 +13,6 @@ This section is new and evolving. The idea here is explore particular use cases
guide_cloudstack
guide_vagrant
guide_rolling_upgrade
guide_docker
Pending topics may include: Docker, Jenkins, Google Compute Engine, Linode/DigitalOcean, Continuous Deployment, and more.