Roles

Roles let you automatically load related vars, files, tasks, handlers, and other Ansible artifacts based on a known file structure. After you group your content in roles, you can easily reuse them and share them with other users.

• Role directory structure
• Storing and finding roles

• Using roles

  • Using roles at the play level
  • Including roles: dynamic reuse
  • Importing roles: static reuse

• Role argument validation

  • Specification format
  • Sample specification

• Running a role multiple times in one playbook

  • Passing different parameters
  • Using allow_duplicates: true

• Using role dependencies

  • Running role dependencies multiple times in one playbook
• Embedding modules and plugins in roles
• Sharing roles: Ansible Galaxy

Role directory structure

An Ansible role has a defined directory structure with eight main standard directories. You must include at least one of these directories in each role. You can omit any directories the role does not use. For example:

# playbooks
site.yml
webservers.yml
fooservers.yml
roles/
    common/
        tasks/
        handlers/
        library/
        files/
        templates/
        vars/
        defaults/
        meta/
    webservers/
        tasks/
        defaults/
        meta/

By default Ansible will look in each directory within a role for a main.yml file for relevant content (also main.yaml and main):

• tasks/main.yml - the main list of tasks that the role executes.
• handlers/main.yml - handlers, which may be used within or outside this role.
• library/my_module.py - modules, which may be used within this role (see Embedding modules and plugins in roles for more information).
• defaults/main.yml - default variables for the role (see Using Variables for more information). These variables have the lowest priority of any variables available, and can be easily overridden by any other variable, including inventory variables.
• vars/main.yml - other variables for the role (see Using Variables for more information).
• files/main.yml - files that the role deploys.
• templates/main.yml - templates that the role deploys.
• meta/main.yml - metadata for the role, including role dependencies.

You can add other YAML files in some directories. For example, you can place platform-specific tasks in separate files and refer to them in the tasks/main.yml file:

# roles/example/tasks/main.yml
- name: Install the correct web server for RHEL
  import_tasks: redhat.yml
  when: ansible_facts['os_family']|lower == 'redhat'

- name: Install the correct web server for Debian
  import_tasks: debian.yml
  when: ansible_facts['os_family']|lower == 'debian'

# roles/example/tasks/redhat.yml
- name: Install web server
  ansible.builtin.yum:
    name: "httpd"
    state: present

# roles/example/tasks/debian.yml
- name: Install web server
  ansible.builtin.apt:
    name: "apache2"
    state: present

Roles may also include modules and other plugin types in a directory called library. For more information, please refer to Embedding modules and plugins in roles below.

Storing and finding roles

By default, Ansible looks for roles in two locations:

• in a directory called roles/, relative to the playbook file
• in /etc/ansible/roles

If you store your roles in a different location, set the roles_path configuration option so Ansible can find your roles. Checking shared roles into a single location makes them easier to use in multiple playbooks. See Configuring Ansible for details about managing settings in ansible.cfg.

Alternatively, you can call a role with a fully qualified path:

---
- hosts: webservers
  roles:
    - role: '/path/to/my/roles/common'

Using roles

You can use roles in three ways:

• at the play level with the roles option: This is the classic way of using roles in a play.
• at the tasks level with include_role: You can reuse roles dynamically anywhere in the tasks section of a play using include_role.
• at the tasks level with import_role: You can reuse roles statically anywhere in the tasks section of a play using import_role.

Using roles at the play level

The classic (original) way to use roles is with the roles option for a given play:

---
- hosts: webservers
  roles:
    - common
    - webservers

When you use the roles option at the play level, for each role ‘x’:

• If roles/x/tasks/main.yml exists, Ansible adds the tasks in that file to the play.
• If roles/x/handlers/main.yml exists, Ansible adds the handlers in that file to the play.
• If roles/x/vars/main.yml exists, Ansible adds the variables in that file to the play.
• If roles/x/defaults/main.yml exists, Ansible adds the variables in that file to the play.
• If roles/x/meta/main.yml exists, Ansible adds any role dependencies in that file to the list of roles.
• Any copy, script, template or include tasks (in the role) can reference files in roles/x/{files,templates,tasks}/ (dir depends on task) without having to path them relatively or absolutely.

When you use the roles option at the play level, Ansible treats the roles as static imports and processes them during playbook parsing. Ansible executes your playbook in this order:

• Any pre_tasks defined in the play.
• Any handlers triggered by pre_tasks.
• Each role listed in roles:, in the order listed. Any role dependencies defined in the role’s meta/main.yml run first, subject to tag filtering and conditionals. See Using role dependencies for more details.
• Any tasks defined in the play.
• Any handlers triggered by the roles or tasks.
• Any post_tasks defined in the play.
• Any handlers triggered by post_tasks.

You can pass other keywords to the roles option:

---
- hosts: webservers
  roles:
    - common
    - role: foo_app_instance
      vars:
        dir: '/opt/a'
        app_port: 5000
      tags: typeA
    - role: foo_app_instance
      vars:
        dir: '/opt/b'
        app_port: 5001
      tags: typeB

When you add a tag to the role option, Ansible applies the tag to ALL tasks within the role.

When using vars: within the roles: section of a playbook, the variables are added to the play variables, making them available to all tasks within the play before and after the role. This behavior can be changed by DEFAULT_PRIVATE_ROLE_VARS.

Including roles: dynamic reuse

You can reuse roles dynamically anywhere in the tasks section of a play using include_role. While roles added in a roles section run before any other tasks in a playbook, included roles run in the order they are defined. If there are other tasks before an include_role task, the other tasks will run first.

To include a role:

---
- hosts: webservers
  tasks:
    - name: Print a message
      ansible.builtin.debug:
        msg: "this task runs before the example role"

    - name: Include the example role
      include_role:
        name: example

    - name: Print a message
      ansible.builtin.debug:
        msg: "this task runs after the example role"

You can pass other keywords, including variables and tags, when including roles:

---
- hosts: webservers
  tasks:
    - name: Include the foo_app_instance role
      include_role:
        name: foo_app_instance
      vars:
        dir: '/opt/a'
        app_port: 5000
      tags: typeA
  ...

When you add a tag to an include_role task, Ansible applies the tag only to the include itself. This means you can pass --tags to run only selected tasks from the role, if those tasks themselves have the same tag as the include statement. See Selectively running tagged tasks in re-usable files for details.

You can conditionally include a role:

---
- hosts: webservers
  tasks:
    - name: Include the some_role role
      include_role:
        name: some_role
      when: "ansible_facts['os_family'] == 'RedHat'"

Importing roles: static reuse

You can reuse roles statically anywhere in the tasks section of a play using import_role. The behavior is the same as using the roles keyword. For example:

---
- hosts: webservers
  tasks:
    - name: Print a message
      ansible.builtin.debug:
        msg: "before we run our role"

    - name: Import the example role
      import_role:
        name: example

    - name: Print a message
      ansible.builtin.debug:
        msg: "after we ran our role"

You can pass other keywords, including variables and tags, when importing roles:

---
- hosts: webservers
  tasks:
    - name: Import the foo_app_instance role
      import_role:
        name: foo_app_instance
      vars:
        dir: '/opt/a'
        app_port: 5000
  ...

When you add a tag to an import_role statement, Ansible applies the tag to all tasks within the role. See Tag inheritance: adding tags to multiple tasks for details.

Role argument validation

Beginning with version 2.11, you may choose to enable role argument validation based on an argument specification. This specification is defined in the meta/argument_specs.yml file (or with the .yaml file extension). When this argument specification is defined, a new task is inserted at the beginning of role execution that will validate the parameters supplied for the role against the specification. If the parameters fail validation, the role will fail execution.

Specification format

The role argument specification must be defined in a top-level argument_specs block within the role meta/argument_specs.yml file. All fields are lower-case.

entry-point-name

• The name of the role entry point.
• This should be main in the case of an unspecified entry point.
• This will be the base name of the tasks file to execute, with no .yml or .yaml file extension.

short_description

• A short, one-line description of the entry point.
• The short_description is displayed by ansible-doc -t role -l.

description

• A longer description that may contain multiple lines.

author

• Name of the entry point authors.
• Use a multi-line list if there is more than one author.

options

• Options are often called “parameters” or “arguments”. This section defines those options.
• For each role option (argument), you may include:

option-name

• The name of the option/argument.

description

• Detailed explanation of what this option does. It should be written in full sentences.

type

• The data type of the option. Default is str.
• If an option is of type list, elements should be specified.

required

• Only needed if true.
• If missing, the option is not required.

default

• If required is false/missing, default may be specified (assumed ‘null’ if missing).
• Ensure that the default value in the docs matches the default value in the code. The actual default for the role variable will always come from defaults/main.yml.
• The default field must not be listed as part of the description, unless it requires additional information or conditions.
• 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.

elements

• Specifies the data type for list elements when type is list.

options

• If this option takes a dict or list of dicts, you can define the structure here.

Sample specification

# roles/myapp/meta/argument_specs.yml
---
argument_specs:
  # roles/myapp/tasks/main.yml entry point
  main:
    short_description: The main entry point for the myapp role.
    options:
      myapp_int:
        type: "int"
        required: false
        default: 42
        description: "The integer value, defaulting to 42."

      myapp_str:
        type: "str"
        required: true
        description: "The string value"

  # roles/maypp/tasks/alternate.yml entry point
  alternate:
    short_description: The alternate entry point for the myapp role.
    options:
      myapp_int:
        type: "int"
        required: false
        default: 1024
        description: "The integer value, defaulting to 1024."

Running a role multiple times in one playbook

Ansible only executes each role once, even if you define it multiple times, unless the parameters defined on the role are different for each definition. For example, Ansible only runs the role foo once in a play like this:

---
- hosts: webservers
  roles:
    - foo
    - bar
    - foo

You have two options to force Ansible to run a role more than once.

Passing different parameters

If you pass different parameters in each role definition, Ansible runs the role more than once. Providing different variable values is not the same as passing different role parameters. You must use the roles keyword for this behavior, since import_role and include_role do not accept role parameters.

This playbook runs the foo role twice:

---
- hosts: webservers
  roles:
    - { role: foo, message: "first" }
    - { role: foo, message: "second" }

This syntax also runs the foo role twice;

---
- hosts: webservers
  roles:
    - role: foo
      message: "first"
    - role: foo
      message: "second"

In these examples, Ansible runs foo twice because each role definition has different parameters.

Using allow_duplicates: true

Add allow_duplicates: true to the meta/main.yml file for the role:

# playbook.yml
---
- hosts: webservers
  roles:
    - foo
    - foo

# roles/foo/meta/main.yml
---
allow_duplicates: true

In this example, Ansible runs foo twice because we have explicitly enabled it to do so.

Using role dependencies

Role dependencies let you automatically pull in other roles when using a role. Ansible does not execute role dependencies when you include or import a role. You must use the roles keyword if you want Ansible to execute role dependencies.

Role dependencies are prerequisites, not true dependencies. The roles do not have a parent/child relationship. Ansible loads all listed roles, runs the roles listed under dependencies first, then runs the role that lists them. The play object is the parent of all roles, including roles called by a dependencies list.

Role dependencies are stored in the meta/main.yml file within the role directory. This file should contain a list of roles and parameters to insert before the specified role. For example:

# roles/myapp/meta/main.yml
---
dependencies:
  - role: common
    vars:
      some_parameter: 3
  - role: apache
    vars:
      apache_port: 80
  - role: postgres
    vars:
      dbname: blarg
      other_parameter: 12

Ansible always executes roles listed in dependencies before the role that lists them. Ansible executes this pattern recursively when you use the roles keyword. For example, if you list role foo under roles:, role foo lists role bar under dependencies in its meta/main.yml file, and role bar lists role baz under dependencies in its meta/main.yml, Ansible executes baz, then bar, then foo.

Running role dependencies multiple times in one playbook

Ansible treats duplicate role dependencies like duplicate roles listed under roles:: Ansible only executes role dependencies once, even if defined multiple times, unless the parameters, tags, or when clause defined on the role are different for each definition. If two roles in a playbook both list a third role as a dependency, Ansible only runs that role dependency once, unless you pass different parameters, tags, when clause, or use allow_duplicates: true in the role you want to run multiple times. See Galaxy role dependencies for more details.

For example, a role named car depends on a role named wheel as follows:

---
dependencies:
  - role: wheel
    n: 1
  - role: wheel
    n: 2
  - role: wheel
    n: 3
  - role: wheel
    n: 4

And the wheel role depends on two roles: tire and brake. The meta/main.yml for wheel would then contain the following:

---
dependencies:
  - role: tire
  - role: brake

And the meta/main.yml for tire and brake would contain the following:

---
allow_duplicates: true

The resulting order of execution would be as follows:

tire(n=1)
brake(n=1)
wheel(n=1)
tire(n=2)
brake(n=2)
wheel(n=2)
...
car

To use allow_duplicates: true with role dependencies, you must specify it for the role listed under dependencies, not for the role that lists it. In the example above, allow_duplicates: true appears in the meta/main.yml of the tire and brake roles. The wheel role does not require allow_duplicates: true, because each instance defined by car uses different parameter values.

Embedding modules and plugins in roles

If you write a custom module (see Should you develop a module?) or a plugin (see Developing plugins), you might wish to distribute it as part of a role. For example, if you write a module that helps configure your company’s internal software, and you want other people in your organization to use this module, but you do not want to tell everyone how to configure their Ansible library path, you can include the module in your internal_config role.

To add a module or a plugin to a role: Alongside the ‘tasks’ and ‘handlers’ structure of a role, add a directory named ‘library’ and then include the module directly inside the ‘library’ directory.

Assuming you had this:

roles/
    my_custom_modules/
        library/
            module1
            module2

The module will be usable in the role itself, as well as any roles that are called after this role, as follows:

---
- hosts: webservers
  roles:
    - my_custom_modules
    - some_other_role_using_my_custom_modules
    - yet_another_role_using_my_custom_modules

If necessary, you can also embed a module in a role to modify a module in Ansible’s core distribution. For example, you can use the development version of a particular module before it is released in production releases by copying the module and embedding the copy in a role. Use this approach with caution, as API signatures may change in core components, and this workaround is not guaranteed to work.

The same mechanism can be used to embed and distribute plugins in a role, using the same schema. For example, for a filter plugin:

roles/
    my_custom_filter/
        filter_plugins
            filter1
            filter2

These filters can then be used in a Jinja template in any role called after ‘my_custom_filter’.

Sharing roles: Ansible Galaxy

Ansible Galaxy is a free site for finding, downloading, rating, and reviewing all kinds of community-developed Ansible roles and can be a great way to get a jumpstart on your automation projects.

The client ansible-galaxy is included in Ansible. The Galaxy client allows you to download roles from Ansible Galaxy, and also provides an excellent default framework for creating your own roles.

Read the Ansible Galaxy documentation page for more information