Ansible Inventory Basics

Ansible is a powerful automation tool that uses inventory files to define the hosts on which tasks will be executed. Understanding how to manage these inventories is crucial for effective automation.

In Ansible, an inventory is a file that contains information about the servers you want to manage. This file can be static (a simple text file) or dynamic (generated by scripts).

Key points:

• Static inventory files are typically in INI or YAML format.
• Dynamic inventories are generated on the fly, often from cloud providers or other external sources.

1. INI Format

# Example of an INI inventory file
[webservers]
web1.example.com
web2.example.com

[dbservers]
db1.example.com
db2.example.com
        

2. YAML Format

# Example of a YAML inventory file
all:
  children:
    webservers:
      hosts:
        web1.example.com:
        web2.example.com:
    dbservers:
      hosts:
        db1.example.com:
        db2.example.com:
        

Dynamic inventories are generated by executing a script (like a Python or shell script) that outputs JSON data. This is useful for cloud environments.

Example command to use a dynamic inventory script:

ansible-playbook -i dynamic_inventory.py playbook.yml

Groups allow you to organize hosts into categories for easier management. You can define group variables and create nested groups.

Example of a group definition in YAML:

all:
  children:
    webservers:
      hosts:
        web1.example.com:
        web2.example.com:
      vars:
        http_port: 80
    dbservers:
      hosts:
        db1.example.com:
        db2.example.com:
        

• Use descriptive names for groups and hosts to improve readability.
• Keep your inventory files organized and well-commented.
• Utilize dynamic inventories for cloud environments.
• Regularly review and update your inventory as your infrastructure changes.