Is it possible to write Ansible hosts/inventory files in YAML?

Question

In the best practices page, there is an example that uses hosts.yml for hosts files:

In the docs, however, I can only find the INI syntax for writing hosts files.

What is the syntax for the inventory files in YAML?

Answer 1

Yes.

It's been deprecated in version 0.6 in 2012 and reintroduced in a commit first included in version 2.1 in 2016.

The example file on GitHub contains the guidelines and examples:

• Comments begin with the '#' character
• Blank lines are ignored
• Top level entries are assumed to be groups
• Hosts must be specified in a group's hosts: and they must be a key (: terminated)
• groups can have children, hosts and vars keys
• Anything defined under a hosts is assumed to be a var
• You can enter hostnames or ip addresses
• A hostname/ip can be a member of multiple groups

Ex 1: Ungrouped hosts, put in 'ungrouped' group

ungrouped:
  hosts:
      green.example.com:
          ansible_ssh_host: 191.168.100.32
      blue.example.com:
      192.168.100.1:
      192.168.100.10:

Ex 2: A collection of hosts belonging to the 'webservers' group

webservers:
  hosts:
      alpha.example.org:
      beta.example.org:
      192.168.1.100:
      192.168.1.110:

Ex 3: You can create hosts using ranges and add children groups and vars to a group. The child group can define anything you would normally add to a group

testing:
  hosts:
      www[001:006].example.com:
  vars:
      testing1: value1
  children:
      webservers:
          hosts:
              beta.example.org:

Answer 2

Previous answers are correct but here is simple hosts.yaml and INI like side by side in the screenshot and I'm just copying the actual hosts.yaml here too so if you want copy and paste and edit it for yourself

--- 
all: 
  hosts:               
    xmp: 
      ansible_connection: ssh
      ansible_host: "192.1.0.1"
      ansible_port: 7822
      ansible_user: nanoseco

some more info:

https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html