Playbooks Introduction

---
# Every playbook starts with --- (YAML document marker)

# A playbook is a list — the first item is the first play
- name: Configure web servers          # play name: shown in output
  hosts: webservers                    # target: all hosts in the webservers group
  become: true                         # all tasks in this play run as root via sudo
  gather_facts: true                   # collect host info before running tasks

  vars:
    nginx_port: 80                     # play-scoped variable — available to all tasks
    server_name: "example.com"

  tasks:
    # Task 1 — install the package
    - name: Install Nginx web server
      ansible.builtin.package:
        name: nginx
        state: present                 # install if missing; skip if already installed

    # Task 2 — write the config file from a template
    - name: Deploy Nginx configuration
      ansible.builtin.template:
        src: nginx.conf.j2             # Jinja2 template on the control node
        dest: /etc/nginx/nginx.conf
        owner: root
        group: root
        mode: "0644"
      notify: Restart Nginx            # trigger the handler if this task changes

    # Task 3 — ensure the service is running and enabled on boot
    - name: Ensure Nginx is started and enabled
      ansible.builtin.service:
        name: nginx
        state: started
        enabled: true

  # Handlers run once at the end of the play, only if notified
  handlers:
    - name: Restart Nginx
      ansible.builtin.service:
        name: nginx
        state: restarted

# Basic run — uses ansible.cfg for inventory and connection settings
ansible-playbook site.yml

# Specify inventory explicitly
ansible-playbook -i inventory/production/hosts.ini site.yml

# Dry run — show what WOULD change without making any changes
ansible-playbook site.yml --check

# Dry run with diff — also shows the exact content changes for files
ansible-playbook site.yml --check --diff

# Limit to a single host or group (override the hosts: in the play)
ansible-playbook site.yml --limit web01.example.com
ansible-playbook site.yml --limit webservers

# Increase verbosity for debugging (-v, -vv, -vvv)
ansible-playbook site.yml -v

# Pass extra variables at runtime
ansible-playbook site.yml -e "nginx_port=8080 server_name=staging.example.com"

---
# Play 1 — configure web servers first
- name: Configure web servers
  hosts: webservers
  become: true
  tasks:
    - name: Install Nginx
      ansible.builtin.package:
        name: nginx
        state: present

# Play 2 — configure databases after web servers are done
- name: Configure database servers
  hosts: databases
  become: true
  tasks:
    - name: Install PostgreSQL
      ansible.builtin.package:
        name: postgresql
        state: present

# Play 3 — run a smoke test against localhost after everything else
- name: Run post-deployment health checks
  hosts: localhost              # run on the control node, not a managed node
  gather_facts: false           # no need to collect facts for a local play
  tasks:
    - name: Verify web servers are responding
      ansible.builtin.uri:
        url: "http://{{ item }}"
        status_code: 200
      loop: "{{ groups['webservers'] }}"