Dynamic Inventory in Ansible allows you to manage and configure your infrastructure dynamically, without the need to manually update static inventory files. This is particularly useful in environments where the infrastructure is constantly changing, such as cloud environments.

1. Static vs. Dynamic Inventory:

   • Static Inventory: A predefined list of hosts and groups in a file.
   • Dynamic Inventory: Inventory is generated dynamically by querying external sources like cloud providers, databases, or other APIs.

2. Inventory Scripts: Custom scripts that generate inventory data dynamically.

3. Inventory Plugins: Built-in or custom plugins that can be used to fetch inventory data from various sources.

• Scalability: Automatically adapt to changes in your infrastructure.
• Flexibility: Integrate with various cloud providers and services.
• Automation: Reduce manual intervention and errors.

1. Create an Inventory Script:

   • Write a script that outputs JSON data in the format expected by Ansible.

   # dynamic_inventory.py
   import json
   
   inventory = {
       "all": {
           "hosts": ["host1.example.com", "host2.example.com"],
           "vars": {
               "ansible_user": "admin"
           }
       },
       "_meta": {
           "hostvars": {
               "host1.example.com": {
                   "ansible_host": "192.168.1.1"
               },
               "host2.example.com": {
                   "ansible_host": "192.168.1.2"
               }
           }
       }
   }
   
   print(json.dumps(inventory))
   

2. Make the Script Executable:

   chmod +x dynamic_inventory.py
   

3. Use the Script in Ansible:

   • Specify the script as the inventory source when running Ansible commands.

   ansible -i dynamic_inventory.py all -m ping
   

1. Enable the Plugin:

   • Ensure the required plugin is enabled in your ansible.cfg file.

   [defaults]
   inventory = ./inventory/aws_ec2.yml
   

2. Configure the Plugin:

   • Create a configuration file for the plugin.

   # inventory/aws_ec2.yml
   plugin: aws_ec2
   regions:
     - us-east-1
   filters:
     instance-state-name: running
   keyed_groups:
     - key: tags.Name
       prefix: tag
   

3. Run Ansible Commands:

   • Use the configuration file as the inventory source.

   ansible -i inventory/aws_ec2.yml all -m ping
   

1. Install Boto3:

   • Ensure you have the boto3 library installed.

   pip install boto3
   

2. Create AWS EC2 Inventory Configuration:

   # inventory/aws_ec2.yml
   plugin: aws_ec2
   regions:
     - us-west-2
   filters:
     instance-state-name: running
   keyed_groups:
     - key: tags.Name
       prefix: tag
   

3. Run Ansible Command:

   ansible -i inventory/aws_ec2.yml all -m ping
   

1. Write a Python script that generates a dynamic inventory for a set of hosts.
2. Make the script executable.
3. Use the script as the inventory source in an Ansible command.

1. Choose a cloud provider plugin (e.g., AWS EC2).
2. Create a configuration file for the plugin.
3. Run an Ansible command using the plugin configuration.

• JSON Format: Ensure your inventory script outputs valid JSON.
• Permissions: Make sure your script is executable.
• Dependencies: Install necessary libraries (e.g., boto3 for AWS).
• Configuration: Double-check your plugin configuration for typos or incorrect settings.

Dynamic Inventory in Ansible provides a powerful way to manage and scale your infrastructure dynamically. By using inventory scripts or plugins, you can automate the process of keeping your inventory up-to-date, reducing manual effort and potential errors. This module has covered the basics of setting up and using dynamic inventory, providing you with the tools to integrate it into your Ansible workflows.