Documentation

Module format and documentation

If you want to contribute your module to Ansible, you must write your module in Python and follow the standard format described below. (Unless you’re writing a Windows module, in which case the Windows guidelines apply.) In addition to following this format, you should review our submission checklist, programming tips, and strategy for maintaining Python 2 and Python 3 compatibility, as well as information about testing before you open a pull request.

Every Ansible module written in Python must begin with seven standard sections in a particular order, followed by the code. The sections in order are:

Note

Why don’t the imports go first?

Keen Python programmers may notice that contrary to PEP 8’s advice we don’t put imports at the top of the file. This is because the ANSIBLE_METADATA through RETURN sections are not used by the module code itself; they are essentially extra docstrings for the file. The imports are placed after these special variables for the same reason as PEP 8 puts the imports after the introductory comments and docstrings. This keeps the active parts of the code together and the pieces which are purely informational apart. The decision to exclude E402 is based on readability (which is what PEP 8 is about). Documentation strings in a module are much more similar to module level docstrings, than code, and are never utilized by the module itself. Placing the imports below this documentation and closer to the code, consolidates and groups all related code in a congruent manner to improve readability, debugging and understanding.

Warning

Copy old modules with care!

Some older modules in Ansible Core have imports at the bottom of the file, Copyright notices with the full GPL prefix, and/or ANSIBLE_METADATA fields in the wrong order. These are legacy files that need updating - do not copy them into new modules. Over time we’re updating and correcting older modules. Please follow the guidelines on this page!

Python shebang

Every Ansible module must begin with #!/usr/bin/python - this “shebang” allows ansible_python_interpreter to work.

ANSIBLE_METADATA block

After the shebang, the copyright, and the license, your module file should contain an ANSIBLE_METADATA section. This section provides information about the module for use by other tools. For new modules, the following block can be simply added into your module:

ANSIBLE_METADATA = {'metadata_version': '1.1',
                    'status': ['preview'],
                    'supported_by': 'community'}

Warning

  • metadata_version is the version of the ANSIBLE_METADATA schema, not the version of the module.
  • Promoting a module’s status or supported_by status should only be done by members of the Ansible Core Team.

Ansible metadata fields

metadata_version:
 

An “X.Y” formatted string. X and Y are integers which define the metadata format version. Modules shipped with Ansible are tied to an Ansible release, so we will only ship with a single version of the metadata. We’ll increment Y if we add fields or legal values to an existing field. We’ll increment X if we remove fields or values or change the type or meaning of a field. Current metadata_version is “1.1”

supported_by:

Who supports the module. Default value is community. For information on what the support level values entail, please see Modules Support. Values are:

  • core
  • network
  • certified
  • community
  • curated (deprecated value - modules in this category should be core or certified instead)
status:

List of strings describing how stable the module is likely to be. See also The lifecycle of an Ansible module. The default value is a single element list [“preview”]. The following strings are valid statuses and have the following meanings:

stableinterface:
 The module’s parameters are stable. Every effort will be made not to remove parameters or change their meaning. Not a rating of the module’s code quality.
preview:The module is in tech preview. It may be unstable, the parameters may change, or it may require libraries or web services that are themselves subject to incompatible changes.
deprecated:The module is deprecated and will be removed in a future release.
removed:The module is not present in the release. A stub is kept so that documentation can be built. The documentation helps users port from the removed module to new modules.

DOCUMENTATION block

After the shebang, the copyright line, the license, and the ANSIBLE_METADATA section comes the DOCUMENTATION block. Ansible’s online module documentation is generated from the DOCUMENTATION blocks in each module’s source code. The DOCUMENTATION block must be valid YAML. You may find it easier to start writing your DOCUMENTATION string in an editor with YAML syntax highlighting before you include it in your Python file. You can start by copying our example documentation string into your module file and modifying it. If you run into syntax issues in your YAML, you can validate it on the YAML Lint website.

Module documentation should briefly and accurately define what each module and option does, and how it works with others in the underlying system. Documentation should be written for broad audience–readable both by experts and non-experts.
  • Descriptions should always start with a capital letter and end with a full stop. Consistency always helps.
  • Verify that arguments in doc and module spec dict are identical.
  • For password / secret arguments no_log=True should be set.
  • If an optional parameter is sometimes required, reflect this fact in the documentation, e.g. “Required when C(state=present).”
  • If your module allows check_mode, reflect this fact in the documentation.

Each documentation field is described below. Before committing your module documentation, please test it at the command line and as HTML:

  • As long as your module file is available locally, you can use ansible-doc -t module my_module_name to view your module documentation at the command line. Any parsing errors will be obvious - you can view details by adding -vvv to the command.
  • You should also test the HTML output of your module documentation.

Documentation fields

All fields in the DOCUMENTATION block are lower-case. All fields are required unless specified otherwise:

module:
  • The name of the module.
  • Must be the same as the filename, without the .py extension.
short_description:
 
  • A short description which is displayed on the All modules page and ansible-doc -l.
  • The short_description is displayed by ansible-doc -l without any category grouping, so it needs enough detail to explain the module’s purpose without the context of the directory structure in which it lives.
  • Unlike description:, short_description should not have a trailing period/full stop.
description:
  • A detailed description (generally two or more sentences).
  • Must be written in full sentences, i.e. with capital letters and periods/full stops.
  • Shouldn’t mention the module name.
version_added:
  • The version of Ansible when the module was added.
  • This is a string, and not a float, i.e. version_added: "2.1"
author:
  • Name of the module author in the form First Last (@GitHubID).
  • Use a multi-line list if there is more than one author.
deprecated:
options:
  • If the module has no options (for example, it’s a _facts module), all you need is one line: options: {}.
  • If your module has options (in other words, accepts arguments), each option should be documented thoroughly. For each module argument/option, include:
option-name:
  • Declarative operation (not CRUD), to focus on the final state, for example online:, rather than is_online:.
  • The name of the option should be consistent with the rest of the module, as well as other modules in the same category.
description:
  • Detailed explanation of what this option does. It should be written in full sentences.
  • Should not list the possible values (that’s what choices: is for, though it should explain what the values do if they aren’t obvious).
  • If an optional parameter is sometimes required this need to be reflected in the documentation, e.g. “Required when I(state=present).”
  • Mutually exclusive options must be documented as the final sentence on each of the options.
required:
  • Only needed if true.
  • If missing, we assume the option is not required.
default:
  • If required is false/missing, default may be specified (assumed ‘null’ if missing).
  • Ensure that the default parameter in the docs matches the default parameter in the code.
  • The default option must not be listed as part of the description.
  • If the option is a boolean value, you can use any of the boolean values recognized by Ansible: (such as true/false or yes/no). Choose the one that reads better in the context of the option.
choices:
  • List of option values.
  • Should be absent if empty.
type:
  • Specifies the data type that option accepts, must match the argspec.
  • If an argument is type='bool', this field should be set to type: bool and no choices should be specified.
aliases:
  • List of optional name aliases.
  • Generally not needed.
version_added:
  • Only needed if this option was extended after initial Ansible release, i.e. this is greater than the top level version_added field.
  • This is a string, and not a float, i.e. version_added: "2.3".
suboptions:
requirements:
  • List of requirements (if applicable).
  • Include minimum versions.
notes:
  • Details of any important information that doesn’t fit in one of the above sections.
  • For example, whether check_mode is or is not supported, or links to external documentation.

Linking within module documentation

You can link from your module documentation to other module docs, other resources on docs.ansible.com, and resources elsewhere on the internet. The correct formats for these links are:

  • L() for Links with a heading. For example: See L(IOS Platform Options guide, ../network/user_guide/platform_ios.html).
  • U() for URLs. For example: See U(https://www.ansible.com/products/tower) for an overview.
  • I() for option names. For example: Required if I(state=present).
  • C() for files and option values. For example: If not set the environment variable C(ACME_PASSWORD) will be used.
  • M() for module names. For example: See also M(win_copy) or M(win_template).

Note

To refer a collection of modules, use C(..), e.g. Refer to the C(win_*) modules.

Documentation fragments

If you’re writing multiple related modules, they may share common documentation, such as authentication details or file mode settings. Rather than duplicate that information in each module’s DOCUMENTATION block, you can save it once as a fragment and use it in each module’s documentation. Shared documentation fragments are contained in a ModuleDocFragment class in lib/ansible/utils/module_docs_fragments/. To include a documentation fragment, add extends_documentation_fragment: FRAGMENT_NAME in your module’s documentation.

For example, all AWS modules should include:

extends_documentation_fragment:
    - aws
    - ec2

You can find more examples by searching for extends_documentation_fragment under the Ansible source tree.

EXAMPLES block

After the shebang, the copyright line, the license, the ANSIBLE_METADATA section, and the DOCUMENTATION block comes the EXAMPLES block. Here you show users how your module works with real-world examples in multi-line plain-text YAML format. The best examples are ready for the user to copy and paste into a playbook. Review and update your examples with every change to your module.

Per playbook best practices, each example should include a name: line:

EXAMPLES = '''
- name: Ensure foo is installed
  modulename:
    name: foo
    state: present
'''

If your module returns facts that are often needed, an example of how to use them can be helpful.

RETURN block

After the shebang, the copyright line, the license, the ANSIBLE_METADATA section, DOCUMENTATION and EXAMPLES blocks comes the RETURN block. This section documents the information the module returns for use by other modules.

If your module doesn’t return anything (apart from the standard returns), this section of your module should read: RETURN = ''' # ''' Otherwise, for each value returned, provide the following fields. All fields are required unless specified otherwise.

return name:

Name of the returned field.

description:Detailed description of what this value represents.
returned:When this value is returned, such as always, or on success.
type:Data type.
sample:One or more examples.
version_added:Only needed if this return was extended after initial Ansible release, i.e. this is greater than the top level version_added field. This is a string, and not a float, i.e. version_added: "2.3".
contains:Optional. To describe nested return values, set type: complex and repeat the elements above for each sub-field.

Here are two example RETURN sections, one with three simple fields and one with a complex nested field:

RETURN = '''
dest:
    description: destination file/path
    returned: success
    type: string
    sample: /path/to/file.txt
src:
    description: source file used for the copy on the target machine
    returned: changed
    type: string
    sample: /home/httpd/.ansible/tmp/ansible-tmp-1423796390.97-147729857856000/source
md5sum:
    description: md5 checksum of the file after running copy
    returned: when supported
    type: string
    sample: 2a5aeecc61dc98c4d780b14b330e3282
'''

RETURN = '''
packages:
    description: Information about package requirements
    returned: On success
    type: complex
    contains:
        missing:
            description: Packages that are missing from the system
            returned: success
            type: list
            sample:
                - libmysqlclient-dev
                - libxml2-dev
        badversion:
            description: Packages that are installed but at bad versions.
            returned: success
            type: list
            sample:
                - package: libxml2-dev
                  version: 2.9.4+dfsg1-2
                  constraint: ">= 3.0"
'''

Python imports

After the shebang, the copyright line, the license, and the sections for ANSIBLE_METADATA, DOCUMENTATION, EXAMPLES, and RETURN, you can finally add the python imports. All modules must use Python imports in the form:

from module_utils.basic import AnsibleModule

The use of “wildcard” imports such as from module_utils.basic import * is no longer allowed.