Ansible easily supports all of these options via an external inventory system. The contrib/inventory directory contains some of these already -- including options for EC2/Eucalyptus, Rackspace Cloud, and OpenStack, examples of some of which will be detailed below.
:ref:`ansible_tower` also provides a database to store inventory results that is both web and REST Accessible. Tower syncs with all Ansible dynamic inventory sources you might be using, and also includes a graphical inventory editor. By having a database record of all of your hosts, it's easy to correlate past event history and see which ones have had failures on their last playbook runs.
It is expected that many Ansible users with a reasonable amount of physical hardware may also be `Cobbler <https://cobbler.github.io>`_ users. (note: Cobbler was originally written by Michael DeHaan and is now led by James Cammarata, who also works for Ansible, Inc).
To tie Ansible's inventory to Cobbler (optional), copy `this script <https://raw.github.com/ansible/ansible/devel/contrib/inventory/cobbler.py>`_ to ``/etc/ansible`` and ``chmod +x`` the file. cobblerd will now need
Also a ``cobbler.ini`` file should be added to ``/etc/ansible`` so Ansible knows where the Cobbler server is and some cache improvements can be used. For example::
First test the script by running ``/etc/ansible/cobbler.py`` directly. You should see some JSON data output, but it may not have anything in it just yet.
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 contact 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"
If you use Amazon Web Services EC2, maintaining an inventory file might not be the best approach, because hosts may come and go over time, be managed by external applications, or you might even be using AWS autoscaling. For this reason, you can use the `EC2 external inventory <https://raw.github.com/ansible/ansible/devel/contrib/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 <https://raw.githubusercontent.com/ansible/ansible/devel/contrib/inventory/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::
If you use Boto profiles to manage multiple AWS accounts, you can pass ``--profile PROFILE`` name to the ``ec2.py`` script. An example profile might be::
Since each region requires its own API call, if you are only using a small set of regions, you can edit the ``ec2.ini`` file and comment out the regions you are not using.
There are other config options in ``ec2.ini``, including cache control and destination variables. By default, the ``ec2.ini`` file is configured for **all Amazon cloud services**, but you can comment out any features that aren't applicable. For example, if you don't have ``RDS`` or ``elasticache``, you can set them to ``False`` ::
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) -- and this is not the most efficient way to manage EC2.
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:
Instances belong to one or more security groups. A group is created for each security group, with all characters except alphanumerics, converted to underscores (_). Each group is prefixed by ``security_group_``. Currently, dashes (-) are also converted to underscores (_). You can change using the replace_dash_in_groups setting in ec2.ini (this has changed across several versions so check the ec2.ini for details).
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``.
To see the complete list of variables available for an instance, run the script by itself::
If you use an OpenStack based cloud, instead of manually maintaining your own inventory file, you can use the openstack_inventory.py dynamic inventory to pull information about your compute instances directly from OpenStack.
You can download the latest version of the OpenStack inventory script `here <https://raw.githubusercontent.com/ansible/ansible/devel/contrib/inventory/openstack_inventory.py>`_.
You can use the inventory script explicitly (by passing the `-i openstack_inventory.py` argument to Ansible) or implicitly (by placing the script at `/etc/ansible/hosts`).
An OpenStack RC file contains the environment variables required by the client tools to establish a connection with the cloud provider, such as the authentication URL, user name, password and region name. For more information on how to download, create or source an OpenStack RC file, please refer to `Set environment variables using the OpenStack RC file <http://docs.openstack.org/user-guide/common/cli_set_environment_variables_using_openstack_rc.html>`_.
The OpenStack command line clients are required to run the `nova list` command. For more information on how to install them, please refer to `Install the OpenStack command-line clients <http://docs.openstack.org/user-guide/common/cli_install_openstack_command_line_clients.html>`_.
Once you confirm the dynamic inventory script is working as expected, you can tell Ansible to use the `openstack_inventory.py` script as an inventory file, as illustrated below::
Note that the OpenStack dynamic inventory script will cache results to avoid repeated API calls. To explicitly clear the cache, you can run the openstack_inventory.py (or hosts) script with the ``--refresh`` parameter::
In an inventory directory, executable files will be treated as dynamic inventory sources and most other files as static sources. Files which end with any of the following will be ignored::
You can replace this list with your own selection by configuring an ``inventory_ignore_extensions`` list in ansible.cfg, or setting the :envvar:`ANSIBLE_INVENTORY_IGNORE` environment variable. The value in either case should be a comma-separated list of patterns, as shown above.
Any ``group_vars`` and ``host_vars`` subdirectories in an inventory directory will be interpreted as expected, making inventory directories a powerful way to organize different sets of configurations.
