If your Ansible inventory fluctuates over time, with hosts spinning up and shutting down in response to business demands, the static inventory solutions described in :ref:`inventory` will not serve your needs. You may need to track hosts from multiple sources: cloud providers, LDAP, `Cobbler <https://cobbler.github.io>`_, and/or enterprise CMDB systems.
Ansible integrates all of these options via a dynamic external inventory system. Ansible supports two ways to connect with external inventory: :ref:`inventory_plugins` and `inventory scripts`.
Inventory plugins take advantage of the most recent updates to the Ansible core code. We recommend plugins over scripts for dynamic inventory. You can :ref:`write your own plugin <developing_inventory>` to connect to additional dynamic inventory sources.
You can still use inventory scripts if you choose. When we implemented inventory plugins, we ensured backwards compatibility via the script inventory plugin. The examples below illustrate how to use inventory scripts.
If you would like a GUI for handling dynamic inventory, the :ref:`ansible_tower` inventory database syncs with all your dynamic inventory sources, provides web and REST access to the results, and offers a graphical inventory editor. With a database record of all of your hosts, you can correlate past event history and see which hosts have had failures on their last playbook runs.
Ansible integrates seamlessly with `Cobbler <https://cobbler.github.io>`_, a Linux installation server originally written by Michael DeHaan and now led by James Cammarata, who works for Ansible.
To tie your Ansible inventory to Cobbler, copy `this script <https://raw.githubusercontent.com/ansible-collections/community.general/main/scripts/inventory/cobbler.py>`_ to ``/etc/ansible`` and ``chmod +x`` the file. Run ``cobblerd`` any time you use Ansible and use the ``-i`` command line option (e.g. ``-i /etc/ansible/cobbler.py``) to communicate with Cobbler using Cobbler's XMLRPC API.
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' are addressable by ansible directly, but are also addressable when using the group names 'webserver' or 'atlanta'. Since Ansible uses SSH, it contacts 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 provides more than 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:
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/openstack/ansible-collections-openstack/master/scripts/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 <https://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 <https://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:
You can find all included inventory scripts in the `contrib/inventory directory <https://github.com/ansible/ansible/tree/stable-2.9/contrib/inventory>`_. General usage is similar across all inventory scripts. You can also :ref:`write your own inventory script <developing_inventory>`.
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. See :ref:`using_multiple_inventory_sources` for more information.
