ansible/dynamic-inventory.md

Dynamic Inventory

Use dynamic inventory to fetch host information at runtime:

Example Usage

- name: Fetch hosts from external source
  ansible.builtin.get_url:
    url: "https://api.example.com/hosts"
    dest: "hosts.json"
  register: inventory_data

- name: Display inventory hosts
  debug:
    var: inventory_data.content

# Example dynamic inventory script (hosts.py):
# import json
# print(json.dumps({"hosts": ["web1", "web2"], "groups": {"webservers": ["web1", "web2"]}}))

Common Inventory Sources

1. EC2 Inventory:

   • Uses AWS API to list instances
   • Parameters: aws_access_key_id, aws_secret_access_key, region
   • Example:

     ansible-inventory --list --inventory=ec2.py
     

2. OpenStack Inventory:

   • Connects to OpenStack neutron API
   • Parameters: auth_url, project_name, username, password
   • Example:

     ansible-inventory --list --inventory=openstack.py
     

3. Custom Scripts:

   • Write Python scripts to generate inventory
   • Must output JSON in this format:

     {
       "hosts": ["host1", "host2"],
       "groups": {
         "webservers": ["host1", "host2"]
       }
     }
     

Best Practices

• Use ansible-inventory --list to verify inventory structure
• Test dynamic inventory with --check flag
• Store credentials securely using Ansible Vault
• Combine with --limit to target specific hosts/groups

Troubleshooting

Use --debug flag to see inventory resolution process:

ansible-playbook site.yml --limit="webservers" --debug