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:orphan:
.. _implicit_localhost:
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.:
.. code-block:: yaml
- 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:
.. code-block:: yaml
...
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``.
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