Vars plugins inject additional variable data into Ansible runs that did not come from an inventory source, playbook, or command line. Playbook constructs like ‘host_vars’ and ‘group_vars’ work using vars plugins. For more details about variables in Ansible, see Using Variables.
Vars plugins were partially implemented in Ansible 2.0 and rewritten to be fully implemented starting with Ansible 2.4.
The host_group_vars plugin shipped with Ansible enables reading variables from Assigning a variable to one machine: host variables and Assigning a variable to many machines: group variables.
You can activate a custom vars plugin by either dropping it into a
vars_plugins directory adjacent to your play, inside a role, or by putting it in one of the directory sources configured in ansible.cfg.
Most vars plugins are disabled by default. To enable a vars plugin, set
vars_plugins_enabled in the
defaults section of ansible.cfg or set the
ANSIBLE_VARS_ENABLED environment variable to the list of vars plugins you want to execute. By default, the host_group_vars plugin shipped with Ansible is enabled.
Starting in Ansible 2.10, you can use vars plugins in collections. All vars plugins in collections must be explicitly enabled and must use the fully qualified collection name in the format
vars_plugins_enabled = host_group_vars,namespace.collection_name.vars_plugin_name
By default, vars plugins are used on demand automatically after they are enabled.
Starting in Ansible 2.10, vars plugins can be made to run at specific times. ansible-inventory does not use these settings, and always loads vars plugins.
The global setting
RUN_VARS_PLUGINS can be set in
run_vars_plugins in the
defaults section or by the
ANSIBLE_RUN_VARS_PLUGINS environment variable. The default option,
demand, runs any enabled vars plugins relative to inventory sources whenever variables are demanded by tasks. You can use the option
start to run any enabled vars plugins relative to inventory sources after importing that inventory source instead.
You can also control vars plugin execution on a per-plugin basis for vars plugins that support the
stage option. To run the host_group_vars plugin after importing inventory you can add the following to ansible.cfg:
stage = inventory
You can use
ansible-doc -t vars -l to see the list of available vars plugins. Use
ansible-doc -t vars <plugin name> to see plugin-specific documentation and examples.