In this section, we will guide you through writing your first Ansible playbook. Playbooks are the heart of Ansible's configuration management and automation capabilities. They allow you to define a series of tasks to be executed on your managed nodes.

A playbook is a YAML file that contains a list of plays. Each play defines a set of tasks to be executed on a group of hosts. Playbooks are designed to be human-readable and can be version-controlled, making them a powerful tool for managing infrastructure as code.

A basic playbook consists of the following components:

1. Hosts: The group of hosts on which the play will run.
2. Tasks: A list of actions to be performed on the hosts.
3. Variables: Values that can be used within tasks to make them more dynamic.

Here is a simple example of a playbook:

• ---: Indicates the start of a YAML document.
• - name: Ensure Apache is installed and running: The name of the play. This is a description of what the play does.
• hosts: webservers: Specifies the group of hosts on which the play will run. This group should be defined in your inventory file.
• become: yes: Indicates that the tasks should be run with elevated privileges (sudo).
• tasks: A list of tasks to be executed on the hosts.
  • - name: Install Apache: The name of the task.
  • apt: The Ansible module used to manage packages on Debian-based systems.
    • name: apache2: The name of the package to be installed.
    • state: present: Ensures that the package is installed.
  • - name: Start Apache service: The name of the task.
  • service: The Ansible module used to manage services.
    • name: apache2: The name of the service to be managed.
    • state: started: Ensures that the service is running.
    • enabled: yes: Ensures that the service is enabled to start at boot.

Let's write a playbook to install and start the Nginx web server on a group of hosts.

1. Create a New Playbook File

   Create a new file named nginx_setup.yml:

   touch nginx_setup.yml
   

2. Define the Play

   Open the file in your favorite text editor and define the play:

   ---
   - name: Ensure Nginx is installed and running
     hosts: webservers
     become: yes
   
     tasks:
       - name: Install Nginx
         apt:
           name: nginx
           state: present
   
       - name: Start Nginx service
         service:
           name: nginx
           state: started
           enabled: yes
   

3. Save and Close the File

   Save the file and close the text editor.

4. Run the Playbook

   Execute the playbook using the ansible-playbook command:

   ansible-playbook -i inventory nginx_setup.yml
   

   Replace inventory with the path to your inventory file.

Exercise: Write a playbook to install and start the MySQL server on a group of hosts.

1. Create a new file named mysql_setup.yml.
2. Define a play to install and start the MySQL server.
3. Save and close the file.
4. Run the playbook using the ansible-playbook command.

Solution:

Run the playbook:

• YAML Syntax Errors: Ensure proper indentation and syntax. YAML is indentation-sensitive.
• Inventory File: Make sure the group names in the playbook match those in your inventory file.
• Module Parameters: Verify that the parameters for each module are correct and supported.

In this section, you learned how to write a basic Ansible playbook to automate the installation and management of services on your hosts. Playbooks are a powerful way to define and manage your infrastructure as code. In the next section, we will delve deeper into the structure of playbooks and explore more advanced features.