What is an Ansible inventory?

An inventory is the list of managed hosts Ansible operates on, organized into groups. It can hold connection details and variables per host or group. Playbooks target groups or hosts from the inventory using the hosts directive.

INI or YAML — which inventory format should I use?

INI is concise and great for simple static inventories. YAML is more expressive for nested groups and complex variable structures. Both are equivalent in capability; this builder generates either from the same data.

What are group variables and children?

Group variables apply to every host in a group, so you set common values like ansible_user once. Children let a group contain other groups, building a hierarchy — for example a production group whose children are webservers and databases.

What is ansible_host used for?

ansible_host overrides the address Ansible connects to, letting the inventory name be a friendly alias while the actual connection uses an IP or different hostname. Other connection vars include ansible_user, ansible_port, and ansible_ssh_private_key_file.

How do I use the generated inventory?

Save it to a file such as inventory.ini or inventory.yml and pass it with ansible-playbook -i inventory.ini site.yml. You can also set it as the default inventory in ansible.cfg so the flag is not needed.

What is the Ansible Inventory File Builder?

Build an Ansible inventory in INI or YAML format with host groups, per-host connection variables, group variables, and children group relationships — ready for ansible-playbook -i. It runs free in your browser on Gera Tools, with nothing uploaded.

Ansible Inventory File Builder

Name: Ansible Inventory File Builder
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Build a correct Ansible inventory, INI or YAML

The inventory tells Ansible which hosts to manage and how to reach them. Getting the group, variable, and children syntax right by hand is fiddly — especially across the INI and YAML formats. This builder lets you model groups, hosts, variables, and hierarchy once and emit either format cleanly.

How it works

In INI format, hosts are listed under a [group] header, group variables go in a [group:vars] section, and nested groups are declared in [group:children]. Per-host variables follow the host name on the same line as key=value pairs. This is the layout Ansible’s ini inventory plugin parses.

In YAML format, everything nests under the implicit all group: all → children → <group> → hosts/vars/children. Each host becomes a mapping whose values are its connection variables. The builder quotes any YAML scalar that could be misread as a number or boolean, so a value like ansible_port: "2222" stays a string when intended.

Side-by-side format comparison

The same three-host setup looks very different in each format, but Ansible parses both identically:

INI

[webservers]
web1 ansible_host=10.0.0.1 ansible_user=ubuntu

[databases]
db1 ansible_host=10.0.0.10 ansible_user=postgres

[production:children]
webservers
databases

[production:vars]
ansible_python_interpreter=/usr/bin/python3

YAML

all:
  children:
    production:
      vars:
        ansible_python_interpreter: /usr/bin/python3
      children:
        webservers:
          hosts:
            web1:
              ansible_host: 10.0.0.1
              ansible_user: ubuntu
        databases:
          hosts:
            db1:
              ansible_host: 10.0.0.10
              ansible_user: postgres

Practical guidance

ansible_host aliases. Name inventory hosts after their role (db-primary) while the real connection goes to an IP. This survives IP changes without touching playbooks.
Group vars vs host vars. Set values shared across a group (like ansible_user) as group vars; override per-host only when one machine genuinely differs. This keeps the inventory readable and prevents per-host sprawl.
Hierarchy for flexible targeting. A production:children group lets hosts: production in a playbook target all sub-groups at once, while individual groups (webservers, databases) remain independently targetable.
Validate before using. Run ansible-inventory -i inventory.yml --list to see the fully-resolved host and variable tree. This catches children loops, missing group references, and YAML quoting mistakes before a playbook run.
Dynamic inventories. For cloud environments, consider pairing this static file with a dynamic plugin (AWS EC2, Azure RM, GCP) so hosts appear automatically as they are provisioned.