jm1.common

Overview Versions Insights

Ansible Role `jm1.common`

This role defines additional facts, e.g. to identify distributions.

Details

New distribution_id fact: A list that uniquely identifies a distribution release. For example:
- distribution_id: [ 'CentOS', '8' ] for CentOS 8 (Core)
- distribution_id: [ 'Debian', '10' ] for Debian 10 (Buster)
- distribution_id: [ 'Debian', '11' ] for Debian 11 (Bullseye)
- distribution_id: [ 'Debian', 'Unstable' ] for Debian Unstable (Sid)
- distribution_id: [ 'Red Hat Enterprise Linux', '8' ] for Red Hat Enterprise Linux (RHEL) 8
- distribution_id: [ 'Ubuntu', '20.04' ] for Ubuntu 20.04 LTS (Focal Fossa)
New distribution_codename fact: A list that stores the distribution codename. For example:
- distribution_codename: [ 'Debian', 'Buster' ] for Debian 10 (Buster)
- distribution_codename: [ 'Ubuntu', 'Focal' ] for Ubuntu 20.04 LTS (Focal Fossa)
NOTE: Not all distributions provide distinct codenames for each release. For example, ansible_facts['distribution_release'] is set to Core for both CentOS 7 and CentOS 8. Hence distribution_codename is not suitable to distinguish between releases, but distribution_id is an unique identifier!

NOTE: On Debian Testing, Unstable aka Sid and Experimental, the fact distribution_id differs depending on whether lsb_release is available or not. If package lsb-release is not installed, then distribution_id|last is always NA for all distributions in development. If lsb_release is available, then distribution_id|last is Testing for Debian Testing and Unstable for Debian Unstable aka Sid and Debian Experimental.
Variables are assigned using set_fact! Mind Ansible's variable precedence: Variables defined with set_fact override variables from most other places such as host_vars and group_vars.

Tested OS images

Cloud images and Docker images of Debian 10 (Buster) [amd64]
Cloud images and Docker images of Debian 11 (Bullseye) [amd64]
Generic cloud image of CentOS 7 (Core) [amd64]
Generic cloud image of CentOS 8 (Core) [amd64]
Ubuntu cloud image of Ubuntu 18.04 LTS (Bionic Beaver) [amd64]
Ubuntu cloud image of Ubuntu 20.04 LTS (Focal Fossa) [amd64]

Available on Ansible Galaxy as jm1.common.

Frequently Asked Questions

Why is distribution_id defined as ansible_facts['distribution_major_version'] on Debian and CentOS but ansible_facts['distribution_version'] on Ubuntu?
How is distribution_id better than ansible_facts['distribution_major_version'] or ansible_facts['distribution_version']?

The intention of distribution_id is to provide a variable that changes whenever a new distribution release might bring breaking changes which demand for updates to Ansible roles, their tasks or default variables. On Debian and CentOS, the ansible_facts['distribution_major_version'] fact is a proper change identifier. However, Ubuntu might introduce breaking changes biannually in April and October, hence ansible_facts['distribution_version'] fits better.

Role jm1.common picks the variable which qualifies best as a change identifier and then assigns its value to distribution_id.
On Debian Testing, Unstable aka Sid and Experimental sometimes the fact distribution_id|last is NA and the other time it is e.g. Testing. Why?

For Debian branches without a version number, e.g. VERSION_ID is not set in /etc/os-release on Debian Testing, Ansible returns different values for ansible_facts['distribution_major_version'] depending on whether the command lsb_release is available on the host. If so, then ansible_facts['distribution_major_version'] resolves to e.g. unstable on Debian Unstable aka Sid. Else ansible_facts['distribution_major_version'] is always NA.

Requirements

None.

Variables

None.

Dependencies

None.

Example Playbook

- hosts: all
  tasks:
    - import_role:
        name: jm1.common
    - debug:
        var: distribution_id

For instructions on how to run Ansible playbooks have look at Ansible's Getting Started Guide.

Example Role

Facts from role jm1.common might help to develop Ansible roles with OS-specific defaults: First off, create OS-agnostic dictionaries in defaults/main.yml. Then use distribution_id as a dict key to assign values for the host OS from dictionaries to default variables. For example:

defaults/main.yml:

image_uri: |-
    {{
        {
            'CentOS 8': 'https://...',
            'Ubuntu 20.04': 'https://...'
        }[distribution_id|join(' ')]
    }}