Inventory: Hosts and Groups

Tell Ansible what exists

The inventory lists the hosts Ansible manages and organises them in groups so you can target them together (web, db, prod). A group can contain other groups with :children, and :vars attaches variables to a group. Inventories can be INI or YAML files, or dynamic scripts/plugins that read from a cloud provider. Use ansible-inventory --graph to see how Ansible understands yours.

An INI inventory

ansible_connection=local is only for this demo. For real servers use their hostnames or IPs and SSH.

[web]
web1 ansible_connection=local
web2 ansible_connection=local

[db]
db1 ansible_connection=local

[prod:children]
web
db

[web:vars]
http_port=8080

How Ansible sees it

I ran ansible-inventory -i inventory.ini --graph on the file above. web and db nest inside prod.

ansible-inventory -i inventory.ini --graph

Output:

@all:
  |--@ungrouped:
  |--@prod:
  |  |--@web:
  |  |  |--web1
  |  |  |--web2
  |  |--@db:
  |  |  |--db1

Quick check: What does `[prod:children]` do in an INI inventory?

• Encrypts the group
• Deletes the prod group
• Creates a new host called children
• Makes the listed groups members of prod