1.. _intro_dynamic_inventory: 2.. _dynamic_inventory: 3 4****************************** 5Working with dynamic inventory 6****************************** 7 8.. contents:: 9 :local: 10 11If 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. 12 13Ansible integrates all of these options through a dynamic external inventory system. Ansible supports two ways to connect with external inventory: :ref:`inventory_plugins` and `inventory scripts`. 14 15Inventory 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. 16 17You can still use inventory scripts if you choose. When we implemented inventory plugins, we ensured backwards compatibility through the script inventory plugin. The examples below illustrate how to use inventory scripts. 18 19If you prefer 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. 20 21.. _cobbler_example: 22 23Inventory script example: Cobbler 24================================= 25 26Ansible 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. 27 28While primarily used to kickoff OS installations and manage DHCP and DNS, Cobbler has a generic 29layer that can represent data for multiple configuration management systems (even at the same time) and serve as a 'lightweight CMDB'. 30 31To tie your Ansible inventory to Cobbler, copy `this script <https://raw.githubusercontent.com/ansible-community/contrib-scripts/main/inventory/cobbler.py>`_ to ``/usr/local/etc/ansible`` and ``chmod +x`` the file. Run ``cobblerd`` any time you use Ansible and use the ``-i`` command line option (for example, ``-i /usr/local/etc/ansible/cobbler.py``) to communicate with Cobbler using Cobbler's XMLRPC API. 32 33Add a ``cobbler.ini`` file in ``/usr/local/etc/ansible`` so Ansible knows where the Cobbler server is and some cache improvements can be used. For example: 34 35.. code-block:: text 36 37 [cobbler] 38 39 # Set Cobbler's hostname or IP address 40 host = http://127.0.0.1/cobbler_api 41 42 # API calls to Cobbler can be slow. For this reason, we cache the results of an API 43 # call. Set this to the path you want cache files to be written to. Two files 44 # will be written to this directory: 45 # - ansible-cobbler.cache 46 # - ansible-cobbler.index 47 48 cache_path = /tmp 49 50 # The number of seconds a cache file is considered valid. After this many 51 # seconds, a new API call will be made, and the cache file will be updated. 52 53 cache_max_age = 900 54 55 56First test the script by running ``/usr/local/etc/ansible/cobbler.py`` directly. You should see some JSON data output, but it may not have anything in it just yet. 57 58Let's explore what this does. In Cobbler, assume a scenario somewhat like the following: 59 60.. code-block:: bash 61 62 cobbler profile add --name=webserver --distro=CentOS6-x86_64 63 cobbler profile edit --name=webserver --mgmt-classes="webserver" --ksmeta="a=2 b=3" 64 cobbler system edit --name=foo --dns-name="foo.example.com" --mgmt-classes="atlanta" --ksmeta="c=4" 65 cobbler system edit --name=bar --dns-name="bar.example.com" --mgmt-classes="atlanta" --ksmeta="c=5" 66 67In the example above, the system 'foo.example.com' is addressable by ansible directly, but is 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 tried "ansible foo", it would not find the system... but "ansible 'foo*'" would do, because the system DNS name starts with 'foo'. 68 69The 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: 70 71.. code-block:: text 72 73 # file: /srv/motd.j2 74 Welcome, I am templated with a value of a={{ a }}, b={{ b }}, and c={{ c }} 75 76Which could be executed just like this: 77 78.. code-block:: bash 79 80 ansible webserver -m setup 81 ansible webserver -m template -a "src=/tmp/motd.j2 dest=/etc/motd" 82 83.. note:: 84 The name 'webserver' came from Cobbler, as did the variables for 85 the config file. You can still pass in your own variables like 86 normal in Ansible, but variables from the external inventory script 87 will override any that have the same name. 88 89So, with the template above (``motd.j2``), this results in the following data being written to ``/etc/motd`` for system 'foo': 90 91.. code-block:: text 92 93 Welcome, I am templated with a value of a=2, b=3, and c=4 94 95And on system 'bar' (bar.example.com): 96 97.. code-block:: text 98 99 Welcome, I am templated with a value of a=2, b=3, and c=5 100 101And technically, though there is no major good reason to do it, this also works: 102 103.. code-block:: bash 104 105 ansible webserver -m ansible.builtin.shell -a "echo {{ a }}" 106 107So, in other words, you can use those variables in arguments/actions as well. 108 109.. _openstack_example: 110 111Inventory script example: OpenStack 112=================================== 113 114If 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. 115 116You 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>`_. 117 118You can use the inventory script explicitly (by passing the `-i openstack_inventory.py` argument to Ansible) or implicitly (by placing the script at `/usr/local/etc/ansible/hosts`). 119 120Explicit use of OpenStack inventory script 121------------------------------------------ 122 123Download the latest version of the OpenStack dynamic inventory script and make it executable:: 124 125 wget https://raw.githubusercontent.com/openstack/ansible-collections-openstack/master/scripts/inventory/openstack_inventory.py 126 chmod +x openstack_inventory.py 127 128.. note:: 129 Do not name it `openstack.py`. This name will conflict with imports from openstacksdk. 130 131Source an OpenStack RC file: 132 133.. code-block:: bash 134 135 source openstack.rc 136 137.. note:: 138 139 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>`_. 140 141You can confirm the file has been successfully sourced by running a simple command, such as `nova list` and ensuring it returns no errors. 142 143.. note:: 144 145 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>`_. 146 147You can test the OpenStack dynamic inventory script manually to confirm it is working as expected:: 148 149 ./openstack_inventory.py --list 150 151After a few moments you should see some JSON output with information about your compute instances. 152 153Once 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: 154 155.. code-block:: bash 156 157 ansible -i openstack_inventory.py all -m ansible.builtin.ping 158 159Implicit use of OpenStack inventory script 160------------------------------------------ 161 162Download the latest version of the OpenStack dynamic inventory script, make it executable and copy it to `/usr/local/etc/ansible/hosts`: 163 164.. code-block:: bash 165 166 wget https://raw.githubusercontent.com/openstack/ansible-collections-openstack/master/scripts/inventory/openstack_inventory.py 167 chmod +x openstack_inventory.py 168 sudo cp openstack_inventory.py /usr/local/etc/ansible/hosts 169 170Download the sample configuration file, modify it to suit your needs and copy it to `/usr/local/etc/ansible/openstack.yml`: 171 172.. code-block:: bash 173 174 wget https://raw.githubusercontent.com/openstack/ansible-collections-openstack/master/scripts/inventory/openstack.yml 175 vi openstack.yml 176 sudo cp openstack.yml /usr/local/etc/ansible/ 177 178You can test the OpenStack dynamic inventory script manually to confirm it is working as expected: 179 180.. code-block:: bash 181 182 /usr/local/etc/ansible/hosts --list 183 184After a few moments you should see some JSON output with information about your compute instances. 185 186Refreshing the cache 187-------------------- 188 189Note 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: 190 191.. code-block:: bash 192 193 ./openstack_inventory.py --refresh --list 194 195.. _other_inventory_scripts: 196 197Other inventory scripts 198======================= 199 200In Ansible 2.10 and later, inventory scripts moved to their associated collections. Many are now in the `community.general scripts/inventory directory <https://github.com/ansible-collections/community.general/tree/main/scripts/inventory>`_. We recommend you use :ref:`inventory_plugins` instead. 201 202.. _using_multiple_sources: 203 204Using inventory directories and multiple inventory sources 205========================================================== 206 207If the location given to ``-i`` in Ansible is a directory (or as so configured in ``ansible.cfg``), Ansible can use multiple inventory sources 208at the same time. When doing so, it is possible to mix both dynamic and statically managed inventory sources in the same ansible run. Instant 209hybrid cloud! 210 211In an inventory directory, executable files are treated as dynamic inventory sources and most other files as static sources. Files which end with any of the following are ignored: 212 213.. code-block:: text 214 215 ~, .orig, .bak, .ini, .cfg, .retry, .pyc, .pyo 216 217You 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 must be a comma-separated list of patterns, as shown above. 218 219Any ``group_vars`` and ``host_vars`` subdirectories in an inventory directory are interpreted as expected, making inventory directories a powerful way to organize different sets of configurations. See :ref:`using_multiple_inventory_sources` for more information. 220 221.. _static_groups_of_dynamic: 222 223Static groups of dynamic groups 224=============================== 225 226When defining groups of groups in the static inventory file, the child groups 227must also be defined in the static inventory file, otherwise ansible returns an 228error. If you want to define a static group of dynamic child groups, define 229the dynamic groups as empty in the static inventory file. For example: 230 231.. code-block:: text 232 233 [tag_Name_staging_foo] 234 235 [tag_Name_staging_bar] 236 237 [staging:children] 238 tag_Name_staging_foo 239 tag_Name_staging_bar 240 241 242.. seealso:: 243 244 :ref:`intro_inventory` 245 All about static inventory files 246 `Mailing List <https://groups.google.com/group/ansible-project>`_ 247 Questions? Help? Ideas? Stop by the list on Google Groups 248 `irc.libera.chat <https://libera.chat/>`_ 249 #ansible IRC chat channel 250