1.1 新版功能.
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
2.2 新版功能.
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:
--check. This is called check_mode: yes.--check. This is called check_mode: no.注解
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 Conditionals) you can check the
potential changes.
2.1 新版功能.
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¶1.1 新版功能.
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