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51 lines
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ReStructuredText
51 lines
2 KiB
ReStructuredText
Check Mode ("Dry Run")
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======================
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.. versionadded:: 1.1
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When ansible-playbook is executed with --check it will not make any changes on remote systems. Instead, any module
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instrumented to support 'check mode' (which contains the primary core modules, but it is not required that all modules do
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this) will report what changes they would have made. Other modules that do not support check mode will also take no
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action, but just will not report what changes they might have made.
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Check mode is just a simulation, and if you have steps that use conditionals that depend on the results of prior commands,
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it may be less useful for you. However it is great for one-node-at-time basic configuration management use cases.
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Example::
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ansible-playbook foo.yml --check
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Running a task in check mode
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````````````````````````````
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.. versionadded:: 1.3
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Sometimes you may want to have a task to be executed even in check
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mode. To achieve this, use the `always_run` clause on the task. Its
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value is a Jinja2 expression, just like the `when` clause. In simple
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cases a boolean YAML value would be sufficient as a value.
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Example::
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tasks:
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- name: this task is run even in check mode
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command: /something/to/run --even-in-check-mode
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always_run: yes
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As a reminder, a task with a `when` clause evaluated to false, will
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still be skipped even if it has a `always_run` clause evaluated to
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true.
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Showing Differences with --diff
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```````````````````````````````
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.. versionadded:: 1.1
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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
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the textual changes made to the file (or, if used with --check, the changes that would have been made). Since the diff
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feature produces a large amount of output, it is best used when checking a single host at a time, like so::
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ansible-playbook foo.yml --check --diff --limit foo.example.com
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