Ansible Fundamentals: Automating Infrastructure Configuration

# Using pip (recommended)# On Ubuntu/Debian# On Ubuntu/Debian# On RHEL/CentOS/Fedora# On RHEL/CentOS/Fedora# On RHEL/CentOS/Fedora# On macOS with Homebrew# On macOS with Homebrew# Verify installation# Verify installationlation
ansible --version

# ansible.cfg - Basic configuration
[defaults]
inventory = ./inventory
remote_user = ansible
host_key_checking = False
retry_files_enabled = False
stdout_callback = yaml

[privilege_escalation]
become = True
become_method = sudo
become_user = root
become_ask_pass = False

# inventory/hosts.ini# Ungrouped hosts# Web servers group# Database servers group# Database servers group# Database servers group# Database servers group# Group with variables# Group with variables# Group with variables# Group with variables# Parent group containing child groups# Parent group containing child groups# Host with connection variables# Host with connection variables# Host with connection variableses
[loadbalancers]
lb1.example.com ansible_user=admin ansible_ssh_private_key_file=~/.ssh/lb_key

# inventory/hosts.yml
all:
  children:
    webservers:
      hosts:
        web1.example.com:
        web2.example.com:
      vars:
        http_port: 80
        max_clients: 200
    dbservers:
      hosts:
        db1.example.com:
          ansible_port: 2222
        db2.example.com:
    production:
      children:
        webservers:
        dbservers:

# aws_ec2.yml - AWS dynamic inventory
plugin: amazon.aws.aws_ec2
regions:
  - eu-west-1
  - eu-west-2
keyed_groups:
  - key: tags.Environment
    prefix: env
  - key: instance_type
    prefix: type
filters:
  instance-state-name: running
compose:
  ansible_host: public_ip_address

# Ping all hosts to verify connectivity# Run a command on all web servers# Using shell module for pipes and redirects# Using shell module for pipes and redirects# Copy a file to all hosts# Copy a file to all hosts# Copy a file to all hosts# Copy a file to all hosts# Install a package on all database servers# Install a package on all database servers# Restart a service# Restart a service# Restart a service# Restart a service# Restart a service# Restart a service# Gather facts about hosts# Gather facts about hosts# Gather facts about hosts# Gather facts about hosts# Filter specific facts# Filter specific facts# Run with elevated privileges# Run with elevated privileges# Limit to specific hosts# Limit to specific hosts# Limit to specific hosts# Limit to specific hosts# Run with specific user# Run with specific user# Run with specific userth specific user
ansible all -m ping -u deploy

# site.yml - Main playbookbook
- name: Configure web servers
  hosts: webservers
  become: yes
  vars:
    http_port: 80
    document_root: /var/www/html

  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present
        update_cache: yes

    - name: Start Nginx service
      service:
        name: nginx
        state: started
        enabled: yes

    - name: Copy website content
      copy:
        src: files/index.html
        dest: "{{ document_root }}/index.html"
        owner: www-data
        group: www-data
        mode: '0644'

- name: Configure database servers
  hosts: dbservers
  become: yes
  
  tasks:
    - name: Install PostgreSQL
      apt:
        name:
          - postgresql
          - postgresql-contrib
        state: present

# Run a playbook# Run with specific inventory# Check mode (dry run)# Check mode (dry run)# Check mode (dry run)# Check mode (dry run)# Verbose output# Verbose output# Verbose output# Verbose output# Limit to specific hosts# Limit to specific hosts# Limit to specific hosts# More detail# Limit to specific hosts# Limit to specific hosts# Limit to specific hosts# Start at specific task# Start at specific task# Start at specific task# List all tasks# List all tasks# List all tasks# List all tasks# List all tasks# List all hosts# List all hosts# List all hostst all hosts
ansible-playbook site.yml --list-hosts

tasks:
  # Simple task
  - name: Ensure Apache is installed
    apt:
      name: apache2
      state: present

  # Task with multiple arguments
  - name: Create application user
    user:
      name: appuser
      shell: /bin/bash
      groups: www-data
      append: yes
      create_home: yes

  # Task with register to capture output
  - name: Get server uptime
    command: uptime
    register: uptime_result

  - name: Display uptime
    debug:
      msg: "Uptime: {{ uptime_result.stdout }}"

  # Task with ignore_errors
  - name: Check if optional service exists
    command: systemctl status optional-service
    register: service_check
    ignore_errors: yes

---
- name: Configure Nginx
  hosts: webservers
  become: yes

  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present

    - name: Copy Nginx configuration
      template:
        src: templates/nginx.conf.j2
        dest: /etc/nginx/nginx.conf
      notify: Restart Nginx

    - name: Copy virtual host configuration
      template:
        src: templates/vhost.conf.j2
        dest: /etc/nginx/sites-available/mysite.conf
      notify:
        - Validate Nginx config
        - Restart Nginx

  handlers:
    - name: Validate Nginx config
      command: nginx -t

    - name: Restart Nginx
      service:
        name: nginx
        state: restarted

# Variables in playbookbook
- name: Deploy application
  hosts: webservers
  vars:
    app_name: myapp
    app_port: 8080
    app_env: production
    
    # Complex variables
    database:
      host: db.example.com
      port: 5432
      name: myapp_db
    
    # List variable
    packages:
      - nginx
      - python3
      - git

  tasks:
    - name: Install packages
      apt:
        name: "{{ packages }}"
        state: present

    - name: Display database host
      debug:
        msg: "Database is at {{ database.host }}:{{ database.port }}"

# group_vars/webservers.yml# host_vars/web1.example.com.yml# host_vars/web1.example.com.yml# host_vars/web1.example.com.yml# Include variables in playbook# Include variables in playbook# Include variables in playbook playbook
- name: Configure servers
  hosts: webservers
  vars_files:
    - vars/common.yml
    - "vars/{{ ansible_os_family }}.yml"

# Using facts in tasks# Conditional based on facts# Conditional based on facts# Conditional based on facts# Conditional based on facts# Conditional based on facts# Conditional based on facts# Conditional based on facts# Conditional based on facts# Conditional based on facts# Custom facts (place in /etc/ansible/facts.d/*.fact)# Custom facts (place in /etc/ansible/facts.d/*.fact)# Custom facts (place in /etc/ansible/facts.d/*.fact)# Custom facts (place in /etc/ansible/facts.d/*.fact)# Custom facts (place in /etc/ansible/facts.d/*.fact)# Custom facts (place in /etc/ansible/facts.d/*.fact)# /etc/ansible/facts.d/app.fact# Access custom facts# Access custom facts# Access custom facts facts
- debug:
    msg: "App version: {{ ansible_local.app.application.version }}"

tasks:
  # Simple condition
  - name: Install Apache on Debian
    apt:
      name: apache2
      state: present
    when: ansible_os_family == "Debian"

  # Multiple conditions (AND)
  - name: Restart service if config changed and in production
    service:
      name: myapp
      state: restarted
    when:
      - config_changed | bool
      - env == "production"

  # OR condition
  - name: Install on Debian or Ubuntu
    apt:
      name: nginx
      state: present
    when: ansible_distribution == "Debian" or ansible_distribution == "Ubuntu"

  # Condition based on registered variable
  - name: Check if file exists
    stat:
      path: /etc/myapp/config.yml
    register: config_file

  - name: Create config if missing
    template:
      src: config.yml.j2
      dest: /etc/myapp/config.yml
    when: not config_file.stat.exists

  # Condition with failed_when
  - name: Run command that might fail
    command: /opt/myapp/check.sh
    register: check_result
    failed_when: "'CRITICAL' in check_result.stdout"

tasks:
  # Simple loop
  - name: Install multiple packages
    apt:
      name: "{{ item }}"
      state: present
    loop:
      - nginx
      - python3
      - git
      - curl

  # Loop with dictionaries
  - name: Create multiple users
    user:
      name: "{{ item.name }}"
      groups: "{{ item.groups }}"
      shell: "{{ item.shell | default('/bin/bash') }}"
    loop:
      - { name: 'alice', groups: 'admin' }
      - { name: 'bob', groups: 'developers' }
      - { name: 'charlie', groups: 'developers,docker' }

  # Loop with index
  - name: Create numbered files
    file:
      path: "/tmp/file_{{ index }}.txt"
      state: touch
    loop:
      - one
      - two
      - three
    loop_control:
      index_var: index

  # Loop with dict2items
  - name: Set sysctl values
    sysctl:
      name: "{{ item.key }}"
      value: "{{ item.value }}"
      state: present
    loop: "{{ sysctl_settings | dict2items }}"
    vars:
      sysctl_settings:
        net.ipv4.ip_forward: 1
        vm.swappiness: 10

  # Nested loops with subelements
  - name: Add SSH keys for users
    authorized_key:
      user: "{{ item.0.name }}"
      key: "{{ item.1 }}"
    loop: "{{ users | subelements('ssh_keys') }}"
    vars:
      users:
        - name: alice
          ssh_keys:
            - "ssh-rsa AAAA... alice@laptop"
            - "ssh-rsa AAAA... alice@desktop"