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community.general/docsite/rst/playbooks_checkmode.rst
Robin Roth 2b28beb1d7 add check_mode option for tasks ()
* add check_mode option for tasks

includes example testcases for the template module

* extend check_mode option

* replace always_run, see also proposal rename_always_run
* rename always_run where used and add deprecation warning
* add some documentation

* have check_mode overwrite always_run

* use unique template name to prevent conflicts

test_check_mode was right before, but failed due to using the same filename as other roles

* still mention always_run in the docs

* set deprecation of always_run to version 2.4

* fix rst style

* expand documentation on per-task check mode
2016-07-22 20:40:14 -04:00

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.. _check_mode_dry:
Check Mode ("Dry Run")
======================
.. versionadded:: 1.1
.. contents:: Topics
When ansible-playbook is executed with ``--check`` it will not make any changes on remote systems. Instead, any module
instrumented to support 'check mode' (which contains most of the primary core modules, but it is not required that all modules do
this) will report what changes they would have made rather than making them. Other modules that do not support check mode will also take no action, but just will not report what changes they might have made.
Check mode is just a simulation, and if you have steps that use conditionals that depend on the results of prior commands,
it may be less useful for you. However it is great for one-node-at-time basic configuration management use cases.
Example::
ansible-playbook foo.yml --check
.. _forcing_to_run_in_check_mode:
Enabling or disabling check mode for tasks
``````````````````````````````````````````
.. versionadded:: 2.2
Sometimes you may want to modify the check mode behavior of individual tasks. This is done via the ``check_mode`` option, which can
be added to tasks.
There are two options:
1. Force a task to **run in check mode**, even when the playbook is called **without** ``--check``. This is called ``check_mode: yes``.
2. Force a task to **run in normal mode** and make changes to the system, even when the playbook is called **with** ``--check``. This is called ``check_mode: no``.
.. note:: Prior to version 2.2 only the the equivalent of ``check_mode: no`` existed. The notation for that was ``always_run: yes``.
Instead of ``yes``/``no`` you can use a Jinja2 expression, just like the ``when`` clause.
Example::
tasks:
- name: this task will make changes to the system even in check mode
command: /something/to/run --even-in-check-mode
check_mode: no
- name: this task will always run under checkmode and not change the system
lineinfile: line="important config" dest=/path/to/myconfig.conf state=present
check_mode: yes
Running single tasks with ``check_mode: yes`` can be useful to write tests for
ansible modules, either to test the module itself or to the the conditions under
which a module would make changes.
With ``register`` (see :doc:`playbooks_conditionals`) you can check the
potential changes.
Information about check mode in variables
`````````````````````````````````````````
.. versionadded:: 2.1
If you want to skip, or ignore errors on some tasks in check mode
you can use a boolean magic variable ``ansible_check_mode``
which will be set to ``True`` during check mode.
Example::
tasks:
- name: this task will be skipped in check mode
git: repo=ssh://git@github.com/mylogin/hello.git dest=/home/mylogin/hello
when: not ansible_check_mode
- name: this task will ignore errors in check mode
git: repo=ssh://git@github.com/mylogin/hello.git dest=/home/mylogin/hello
ignore_errors: "{{ ansible_check_mode }}"
.. _diff_mode:
Showing Differences with ``--diff``
```````````````````````````````````
.. versionadded:: 1.1
The ``--diff`` option to ansible-playbook works great with ``--check`` (detailed above) but can also be used by itself. When this flag is supplied, if any templated files on the remote system are changed, and the ansible-playbook CLI will report back
the textual changes made to the file (or, if used with ``--check``, the changes that would have been made). Since the diff
feature produces a large amount of output, it is best used when checking a single host at a time, like so::
ansible-playbook foo.yml --check --diff --limit foo.example.com