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Generating the Inventory

The script that creates the inventory is located at inventory/dynamic_inventory.py and installed into the ansible-runtime virtualenv as openstack-ansible-inventory.

This section explains how ansible runs the inventory, and how you can run it manually to see its behavior.

Executing the dynamic_inventory.py script manually

When running an Ansible command (such as ansible, ansible-playbook or openstack-ansible) Ansible automatically executes the dynamic_inventory.py script and use its output as inventory.

Run the following command:

# from the root folder of cloned OpenStack-Ansible repository
inventory/dynamic_inventory.py --config /etc/openstack_deploy/

Dynamic inventory script is also installed inside virtualenv as a script. So alternatively you can run following:

source /opt/ansible-runtime/bin/activate
openstack-ansible-inventory --config /etc/openstack_deploy/

This invocation is useful when testing changes to the dynamic inventory script.


The dynamic_inventory.py takes the --config argument for the directory holding configuration from which to create the inventory. If not specified, the default is /etc/openstack_deploy/.

In addition to this argument, the base environment skeleton is provided in the inventory/env.d directory of the OpenStack-Ansible codebase.

Should an env.d directory be found in the directory specified by --config, its contents will be added to the base environment, overriding any previous contents in the event of conflicts.


In all versions prior to Wallaby, this argument was --file.

The following file must be present in the configuration directory:

  • openstack_user_config.yml

Additionally, the configuration or environment could be spread between two additional sub-directories:

  • conf.d

  • env.d (for environment customization)

The dynamic inventory script does the following:

  • Generates the names of each container that runs a service

  • Creates container and IP address mappings

  • Assigns containers to physical hosts

As an example, consider the following excerpt from openstack_user_config.yml:


The identity_hosts dictionary defines an Ansible inventory group named identity_hosts containing the three infra hosts. The configuration file inventory/env.d/keystone.yml defines additional Ansible inventory groups for the containers that are deployed onto the three hosts named with the prefix infra.

Note that any services marked with is_metal: true will run on the allocated physical host and not in a container. For an example of is_metal: true being used refer to inventory/env.d/cinder.yml in the container_skel section.

For more details, see Configuring the inventory.


Once executed, the script will output an openstack_inventory.json file into the directory specified with the --config argument. This is used as the source of truth for repeated runs.


The openstack_inventory.json file is the source of truth for the environment. Deleting this in a production environment means that the UUID portion of container names will be regenerated, which then results in new containers being created. Containers generated under the previous version will no longer be recognized by Ansible, even if reachable via SSH.

The same JSON structure is printed to stdout, which is consumed by Ansible as the inventory for the playbooks.

Checking inventory configuration for errors

Using the --check flag when running dynamic_inventory.py will run the inventory build process and look for known errors, but not write any files to disk.

If any groups defined in the openstack_user_config.yml or conf.d files are not found in the environment, a warning will be raised.

This check does not do YAML syntax validation, though it will fail if there are unparseable errors.

Writing debug logs

The --debug/-d parameter allows writing of a detailed log file for debugging the inventory script’s behavior. The output is written to inventory.log in the current working directory.

The inventory.log file is appended to, not overwritten.

Like --check, this flag is not invoked when running from ansible.

Running with tox

In some cases you might want to generate inventory on operator local machines after altering openstack_user_config.yml or env.d/conf.d files. Given that you already have openstack_deploy directory on such machine, you can create tox.ini file in that directory with following content:

envlist = generate_inventory

skip_install = True
usedevelop = True
allowlist_externals =

basepython = python3
deps = -rhttps://opendev.org/openstack/openstack-ansible/raw/branch/master/requirements.txt
install_command =
    pip install -c https://releases.openstack.org/constraints/upper/master {packages} git+https://opendev.org/openstack/openstack-ansible@master
commands =
    osa-dynamic-inventory --config {toxinidir}

Then you can run a command to generate inventory using tox:

tox -e generate_inventory

As a result you will get your openstack_user_config.json updated. You can use this method also to verify validity of the inventory.