Inventory Patterns in Ansible

1. Introduction

Ansible uses an inventory to manage machines and environments. Understanding inventory patterns helps in efficiently managing resources and applying configurations to the correct hosts.

2. Types of Inventory

There are two primary types of inventory in Ansible:

• Static Inventory
• Dynamic Inventory

2.1 Static Inventory

Static inventory is defined in a simple text file (usually in INI or YAML format) listing the hosts and their properties.

[webservers]
192.168.1.1
192.168.1.2
192.168.1.3

2.2 Dynamic Inventory

Dynamic inventory is generated by scripts or external sources such as cloud providers or configuration management databases (CMDB).

3. Inventory Sources

Inventory can be sourced from several locations:

• INI Files
• YAML Files
• Scripts
• Cloud Providers

4. Inventory Patterns

Inventory patterns allow users to define groups and hierarchies within their inventory, making it easier to organize hosts based on their roles and environments.

4.1 Grouping

Grouping allows you to categorize hosts. You can define groups in your static inventory as follows:

[databases]
db1.example.com
db2.example.com

[webservers]
web1.example.com
web2.example.com

4.2 Nested Groups

Nested groups can be defined to create a hierarchy:

[all:children]
databases
webservers

[all:vars]
ansible_user=admin

4.3 Pattern Matching

Ansible allows pattern matching to select hosts. For example, using ansible-playbook with patterns:

ansible-playbook playbook.yml -i inventory.ini webservers

5. Best Practices

To effectively manage Ansible inventories, follow these best practices:

• Use descriptive names for groups and hosts.
• Organize inventory files into environment-specific directories.
• Utilize dynamic inventories when dealing with cloud resources.
• Regularly review and update inventory files to reflect changes in the infrastructure.

6. FAQ