What is an inventory file in Ansible, and how do you configure and use it

1. What is an Ansible Inventory File in Control node.

An inventory file lists servers and devices(Manage nodes) Ansible manages in Control node. It can be static or dynamic, specifying IPs, domains, and SSH details.

2. Default Inventory File Location

Ansible’s default inventory file is at:

    /etc/ansible/hosts

Users can specify a different location when using custom inventory file with:

    ansible -i custom_inventory.ini all --list-hosts
Note: It is recommended to use custom inventory file for different project
      or for different group of server 

3. Inventory File Formats

• INI (Simple, widely used)

• YAML (Hierarchical, better for large setups)

• JSON (API-friendly, less common)

4. INI Format Example

[web]

192.168.1.10

192.168.1.11

[database]

db1.example.com

db2.example.com

[all:vars]

ansible_user=ubuntu

ansible_ssh_private_key_file=~/.ssh/id_rsa

5. YAML Format Example

all:

  hosts:

    web1:

      ansible_host: 192.168.1.10

  vars:

    ansible_user: ubuntu

6. Host Grouping and Variables

Grouping hosts simplifies automation:

[web_servers]

web1.example.com

[db_servers]

db1.example.com

7. Dynamic Inventory

For cloud infrastructure, use plugins like AWS, Azure:

    ansible-inventory -i aws_ec2.yml --list

8. Running Commands with Inventory

Test connectivity:

ansible -i inventory.ini all -m ping

Execute a quick command:

ansible -i inventory.ini web -m shell -a "uptime"

9. Using Inventory in Playbooks

- name: Install Nginx

  hosts: web

  tasks:

    - name: Install Nginx

      apt:

        name: nginx

        state: present

Run with:

ansible-playbook -i inventory.ini playbook.yml

10. Debugging and Security

View inventory:

ansible-inventory -i inventory.ini --list

Encrypt sensitive data:

ansible-vault encrypt inventory.yml

11. Best Practices

• Structure inventory files properly.

• Separate dev and production environments.

• Use dynamic inventory for cloud-based infrastructure.

12. Conclusion

Ansible’s inventory file is essential for automating server management. Proper structuring, grouping, and variable usage enhance efficiency in IT automation.

Important Link : Ansible Ad-hoc command