13. Basic Inventory Configuration in Ansible

In the previous article, we explored how to use loops and conditional statements when writing Ansible Playbooks. In this article, we’ll dive deeper into Ansible Inventory files—specifically, how to configure basic static Inventory. Mastering Inventory configuration is essential for effectively managing and executing Ansible Playbooks.

What Is an Inventory?

In Ansible, an Inventory is a list used to define and organize your target hosts and their groupings. Ansible uses the Inventory to determine which hosts should execute a given task. You can use either a static Inventory file (typically in INI or YAML format) or a dynamic Inventory script.

Basic Static Inventory Configuration

A static Inventory is usually stored in a plain-text file, configurable using either simple INI or YAML syntax. Below, we demonstrate basic Inventory configuration through practical examples.

Example 1: INI-Format Inventory

Suppose you have three servers with IP addresses 192.168.1.10, 192.168.1.11, and 192.168.1.12. You can create a file named inventory.ini with the following content:

[web_servers]
web1 ansible_host=192.168.1.10
web2 ansible_host=192.168.1.11

[db_servers]
db1 ansible_host=192.168.1.12

In this example, we define two groups: web_servers and db_servers. The ansible_host keyword specifies the IP address of each host.

Example 2: YAML-Format Inventory

The same configuration can be expressed in YAML format by creating a file named inventory.yml:

all:
  children:
    web_servers:
      hosts:
        web1:
          ansible_host: 192.168.1.10
        web2:
          ansible_host: 192.168.1.11
    db_servers:
      hosts:
        db1:
          ansible_host: 192.168.1.12

YAML’s hierarchical structure makes group–host relationships more explicit and easier to read.

Executing Ansible Commands Using an Inventory

Once your Inventory is configured, you can use the ansible command-line tool to run ad-hoc tasks. For instance, to ping all hosts in the web_servers group, run:

ansible web_servers -i inventory.ini -m ping

This command targets all hosts in the web_servers group and executes the ping module on each.

Assigning Variables to Hosts

In real-world scenarios, you often need to assign specific variables to individual hosts. You can declare such variables directly within your Inventory file. For example, to assign an environment variable env to web1, update inventory.ini as follows:

[web_servers]
web1 ansible_host=192.168.1.10 env=production
web2 ansible_host=192.168.1.11 env=staging

Within a Playbook, you can reference these values using {{ ansible_host }} or {{ env }}.

Conclusion

In this section, we covered how to configure basic static Inventory files, how to group hosts, and how to assign host-specific variables. These foundational concepts prepare you for writing robust Ansible Playbooks—and serve as a stepping stone toward leveraging dynamic Inventory in more advanced deployments.

In the next tutorial, we’ll explore dynamic Inventory—enhancing Ansible’s flexibility and scalability. Stay tuned for the rest of this series!