The remainder of features in the API docs have components available in `ansible-plugins <https://github.com/ansible/ansible/blob/devel/plugins>`_. Send us a github pull request if you develop any interesting features.
of these options via an external inventory system. The plugins directory contains some of these already -- including options for EC2/Eucalyptus and OpenStack, which will be detailed below.
It's possible to write an external inventory script in any language. If you are familiar with Puppet terminology, this concept is basically the same as 'external nodes', with the slight difference that it also defines which hosts are managed.
When the external node script is called with the single argument '--list', the script must return a JSON hash/dictionary of all the groups to be managed, with a list of each host/IP as the value for each hash/dictionary element, like so::
To tie Ansible's inventory to Cobbler (optional), copy `this script <https://raw.github.com/ansible/ansible/devel/plugins/inventory/cobbler.py>`_ to /etc/ansible/hosts and `chmod +x` the file. cobblerd will now need
cobbler system edit --name=foo --dns-name="foo.example.com" --mgmt-classes="atlanta" --ksmeta="c=4"
cobbler system edit --name=bar --dns-name="bar.example.com" --mgmt-classes="atlanta" --ksmeta="c=5"
In the example above, the system 'foo.example.com' will be addressable by ansible directly, but will also be addressable when using the group names 'webserver' or 'atlanta'. Since Ansible uses SSH, we'll try to contract system foo over 'foo.example.com', only, never just 'foo'. Similarly, if you try "ansible foo" it wouldn't find the system... but "ansible 'foo*'" would, because the system DNS name starts with 'foo'.
The script doesn't just provide host and group info. In addition, as a bonus, when the 'setup' module is run (which happens automatically when using playbooks), the variables 'a', 'b', and 'c' will all be auto-populated in the templates::
# file: /srv/motd.j2
Welcome, I am templated with a value of a={{ a }}, b={{ b }}, and c={{ c }}
Which could be executed just like this::
ansible webserver -m setup
ansible webserver -m template -a "src=/tmp/motd.j2 dest=/etc/motd"
So that's the Cobbler integration support -- using the cobbler script as an example, it should be trivial to adapt Ansible to pull inventory, as well as variable information, from any data source. If you create anything interesting, please share with the mailing list, and we can keep it in the source code tree for others to use.
If you use Amazon Web Services EC2, maintaining an inventory file might not be the best approach. For this reason, you can use the `EC2 external inventory <https://raw.github.com/ansible/ansible/devel/plugins/inventory/ec2.py>`_ script.
The second option is to copy the script to `/etc/ansible/hosts` and `chmod +x` it. You will also need to copy the ``ec2.ini`` file to `/etc/ansible/ec2.ini`. Then you can run ansible as you would normally.
To successfully make an API call to AWS, you will need to configure Boto (the Python interface to AWS). There are a `variety of methods <http://docs.pythonboto.org/en/latest/boto_config_tut.html>`_ available, but the simplest is just to export two environment variables:
Since each region requires its own API call, if you are only using a small set of regions, feel free to edit ``ec2.ini`` and list only the regions you are interested in. There are other config options in ``ec2.ini`` including cache control, and destination variables.
At their heart, inventory files are simply a mapping from some name to a destination address. The default ``ec2.ini`` settings are configured for running Ansible from outside EC2 (from your laptop for example). If you are running Ansible from within EC2, internal DNS names and IP addresses may make more sense than public DNS names. In this case, you can modify the ``destination_variable`` in ``ec2.ini`` to be the private DNS name of an instance. This is particularly important when running Ansible within a private subnet inside a VPC, where the only way to access an instance is via its private IP address. For VPC instances, `vpc_destination_variable` in ``ec2.ini`` provides a means of using which ever `boto.ec2.instance variable <http://docs.pythonboto.org/en/latest/ref/ec2.html#module-boto.ec2.instance>`_ makes the most sense for your use case.
The EC2 external inventory provides mappings to instances from several groups:
Instance ID
These are groups of one since instance IDs are unique.
e.g.
``i-00112233``
``i-a1b1c1d1``
Region
A group of all instances in an AWS region.
e.g.
``us-east-1``
``us-west-2``
Availability Zone
A group of all instances in an availability zone.
e.g.
``us-east-1a``
``us-east-1b``
Security Group
Instances belong to one or more security groups. A group is created for each security group, with all characters except alphanumerics, dashes (-) converted to underscores (_). Each group is prefixed by ``security_group_``
e.g.
``security_group_default``
``security_group_webservers``
``security_group_Pete_s_Fancy_Group``
Tags
Each instance can have a variety of key/value pairs associated with it called Tags. The most common tag key is 'Name', though anything is possible. Each key/value pair is its own group of instances, again with special characters converted to underscores, in the format ``tag_KEY_VALUE``
When the Ansible is interacting with a specific server, the EC2 inventory script is called again with the ``--host HOST`` option. This looks up the HOST in the index cache to get the instance ID, and then makes an API call to AWS to get information about that specific instance. It then makes information about that instance available as variables to your playbooks. Each variable is prefixed by ``ec2_``. Here are some of the variables available:
- ec2_architecture
- ec2_description
- ec2_dns_name
- ec2_id
- ec2_image_id
- ec2_instance_type
- ec2_ip_address
- ec2_kernel
- ec2_key_name
- ec2_launch_time
- ec2_monitored
- ec2_ownerId
- ec2_placement
- ec2_platform
- ec2_previous_state
- ec2_private_dns_name
- ec2_private_ip_address
- ec2_public_dns_name
- ec2_ramdisk
- ec2_region
- ec2_root_device_name
- ec2_root_device_type
- ec2_security_group_ids
- ec2_security_group_names
- ec2_spot_instance_request_id
- ec2_state
- ec2_state_code
- ec2_state_reason
- ec2_status
- ec2_subnet_id
- ec2_tag_Name
- ec2_tenancy
- ec2_virtualization_type
- ec2_vpc_id
Both ``ec2_security_group_ids`` and ``ec2_security_group_names`` are comma-separated lists of all security groups. Each EC2 tag is a variable in the format ``ec2_tag_KEY``.
Though not detailed here in as much depth as the EC2 module, there's also a OpenStack Nova external inventory source in the plugins directory. See the inline comments in the module source for how to use it.
Language constructs like "with_fileglob" and "with_items" are implemented via lookup plugins. Just like other plugin types, you can write your own.
Vars Plugins
------------
Playbook constructs like 'host_vars' and 'group_vars' work via 'vars' plugins. They inject additional variable
data into ansible runs that did not come from an inventory, playbook, or command line. Note that variables
can also be returned from inventory, so in most cases, you won't need to write or understand vars_plugins.
Filter Plugins
--------------
If you want more Jinja2 filters available in a Jinja2 template (filters like to_yaml and to_json are provided by default), they can be extended by writing a filter plugin.
