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Inventories

Inventories

Inventories instruct Ansible on how to interact with your infrastructure, describing things like the path to a Python interpreter on the remote host, the SSH user Ansible should connect as and which SSH key to use, variables for your playbooks and roles, as well as custom/arbitrary variable declaration for things like software versions (if a play/role installs a specific version of a piece of software), secrets/tokens, & more.

Variables are declared in a directory alongside the inventory file, group_vars/all.yml. You can add other .yml files for variables, and Ansible will “join” them all when running plays.

Note

There are multiple ways to create your inventory. Ansible supports inventory files described in ini and yaml.

I have used both, but more recently prefer yaml for describing my inventory. This guide assumes you will also use yaml inventories, but if you choose to use ini instead, you can translate the configurations by referencing the Ansible documentation.

Example inventories

Example: simple inventory 

---
## A group for all machines in this inventory.
#  You can call these hosts in groups within this inventory after declaring here
all:
  ## Describe your hosts
  host1:
    ## Set the host IP/FQDN Ansible will use to connect
    ansible_host: "192.168.1.xxx"
  host2:
    ansible_host: "192.168.1.xxx"
    ## Override the remote machine's user Ansible will run as
    ansible_user: "username"
  host3:
    ansible_host: "192.168.1.xxx"
    ## Override the example_var_int value for just this host
    example_var_int: 42

  ## Vars that apply to all hosts.
  #  Can be overridden at the host definition or group level
  vars:
    ## Set variables Ansible will pass to plays/roles when this inventory is used
    #  Call in a playbook/role with {{ example_var }} or {{ example_var_int }}
    example_var: "I'm an example string"
    example_var_int: 100
  
## Group hosts declared in 'all' for controlling execution
#  with ansible-playbook -i inventory.yml --limit <group-name>
debian:
  ## You can just use the hostname from 'all'. Any vars declared at this level
  #  will override values set in 'all' definition
  host1:
  host3:
    example_var: "My value is now this string, and example_var_int will be 42 because it was overridden in the 'all' group"

## If you use a service like DigitalOcean, you can create a group for those hosts
digitalOcean:
  host2:
    ## You can add variables you haven't declared yet
    example_bool: true
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