Ansible Conditionals based on facts variables re use

• detect target operating systems and versions using facts,
• apply environment-specific configuration using variables,
• reuse common tasks while running environment-specific steps only where appropriate.

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Facts: What they are and how to use them

• Ansible user guide — conditionals: https://docs.ansible.com/ansible/latest/user_guide/playbooks_conditionals.html
• Facts & the setup module: https://docs.ansible.com/ansible/latest/collections/ansible/builtin/setup_module.html

• ansible <host-pattern> -m setup Or by adding a debug task to a play:

- name: Show gathered facts
  debug:
    var: ansible_facts

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Scenario 1 — Install Nginx only on Ubuntu 18.04

- name: Install Nginx on Ubuntu 18.04
  apt:
    name: nginx=1.18.0
    state: present
  when:
    - ansible_facts['distribution'] == 'Ubuntu'
    - ansible_facts['distribution_major_version'] == '18'

• For targeting all Debian-family distributions you could use ansible_facts['os_family'] == 'Debian'.
• Always validate the exact fact keys by inspecting gathered facts on your hosts.

• apt module: https://docs.ansible.com/ansible/latest/collections/ansible/builtin/apt_module.html

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Scenario 2 — Use a variable to apply environment-specific configuration

- name: Deploy environment-specific config
  template:
    src: "{{ app_env }}_config.j2"
    dest: /etc/myapp/config.conf
  vars:
    # optionally override per-task (prefer inventory/group_vars for real deployments)
    # app_env: production

• inventory (host_vars or group_vars)
• dedicated variable files
• at the play level:

vars:
  app_env: production

• template module: https://docs.ansible.com/ansible/latest/collections/ansible/builtin/template_module.html

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Scenario 3 — Reuse common tasks, but start services only in production

- name: Deploy myapp across mixed servers
  hosts: all
  become: yes
  vars:
    app_env: production    # in real deployments, set this per-inventory/host_vars
  tasks:
    - name: Install required packages (Debian-family)
      apt:
        name:
          - package1
          - package2
        state: present
      when: ansible_facts['os_family'] == 'Debian'

    - name: Create necessary directories and set permissions
      file:
        path: /opt/myapp
        state: directory
        owner: myapp
        group: myapp
        mode: '0755'

    - name: Deploy environment-specific config
      template:
        src: "{{ app_env }}_config.j2"
        dest: /etc/myapp/config.conf
      notify: Restart myapp

    - name: Start web application service (only in production)
      service:
        name: myapp
        state: started
      when: app_env == 'production'

  handlers:
    - name: Restart myapp
      service:
        name: myapp
        state: restarted

• Replace the apt task with yum or win_chocolatey on non-Debian systems when needed.
• Use notify + handlers to centralize service restarts after configuration changes.

• https://docs.ansible.com/ansible/latest/collections/ansible/builtin/service_module.html

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Best practices and tips

• Keep environment and role variables out of inline tasks. Prefer inventory (host_vars / group_vars) or dedicated variable files to make playbooks reusable and easy to manage.
• Use consistent variable names across repositories (e.g., app_env or environment) to avoid confusion.
• Inspect facts frequently with the setup module or debug to determine which fact names and values are available on your target hosts.
• Use multiple when conditions as lists for readability: when:
  • condition1
  • condition2
• Prefer checking os_family for portability across similar distributions, and use distribution + distribution_major_version for precise control.

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Summary

• Ansible documentation: https://docs.ansible.com/ansible/latest/index.html
• Playbooks and conditionals: https://docs.ansible.com/ansible/latest/user_guide/playbooks_conditionals.html