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# Implicit ‘localhost’

When you try to reference a `localhost` and you don’t have it defined in inventory, Ansible will create an implicit one for you.:

    - hosts: all
      tasks:
        - name: check that i have log file for all hosts on my local machine
          stat: path=/var/log/hosts/{{inventory_hostname}}.log
          delegate_to: localhost

In a case like this (or `local_action`) when Ansible needs to contact a ‘localhost’ but you did not supply one, we create one for you. This host is defined with specific connection variables equivalent to this in an inventory:

    ...

    hosts:
      localhost:
       vars:
         ansible_connection: local
         ansible_python_interpreter: "{{ansible_playbook_python}}"

This ensures that the proper connection and Python are used to execute your tasks locally. You can override the built-in implicit version by creating a `localhost` host entry in your inventory. At that point, all implicit behaviors are ignored; the `localhost` in inventory is treated just like any other host. Group and host vars will apply, including connection vars, which includes the `ansible_python_interpreter` setting. This will also affect `delegate_to: localhost` and `local_action`, the latter being an alias to the former.

Note

- This host is not targetable via any group, however it will use vars from `host_vars` and from the ‘all’ group.

- Implicit localhost does not appear in the `hostvars` magic variable unless demanded, such as by `"{{ hostvars['localhost'] }}"`.

- The `inventory_file` and `inventory_dir` magic variables are not available for the implicit localhost as they are dependent on each inventory host.

- This implicit host also gets triggered by using `127.0.0.1` or `::1` as they are the IPv4 and IPv6 representations of ‘localhost’.

- Even though there are many ways to create it, there will only ever be ONE implicit localhost, using the name first used to create it.

- Having `connection: local` does NOT trigger an implicit localhost, you are just changing the connection for the `inventory_hostname`.