Vars and Facts

Vars

Magic variables

Commonly used magic variables include hostvars, groups, group_names, and inventory_hostname. groups is a list of all the groups (and hosts) in the inventory.

• inventory_dir is the pathname of the directory holding Ansible’s inventory host file
• inventory_file is the pathname and the filename pointing to the Ansible’s inventory host file.
• inventory_hostname is the name of the target host for the current play. This is the remote target even when the task uses delegate_to.
• inventory_hostname_short is useful if your host has a long fqdn and you only need the hostname up to the first period. Note this comes from the inventory, not from the target host, useful if gather_facts is disabled.
• ansible_hostname is a discovered fact from the remote host, so not available with gather_facts disabled.

See the ansible docs for more details.

Group and Host Variables

See documentation for playbooks best practices.

inventory/group_vars/all.yaml my_var_name: "some value"

Use {{ hostvars[inventory_hostname]['my_var_name'] }} to reference. Note the group_vars/all structure does not mean there is an [all] hosts group to reference, but the vars in all will get applied to all group (hosts), and can be referenced using the magic variable inventory_hostname. Note the use of single quotes for the my_var_name (which is looking up the string 'my_var_name') vs the [inventory_hostname] syntax to index the inventory_hostname in the hostvars array.

Load variables from a file

On the command line, use -e or --extra-vars. Set additional variables as key=value or YAML/JSON, if filename prepend the filename with @.

ansible-playbook ... --extra-vars '@my-vars.yaml'

Combine vars from a file and additional vars by using --extra-vars twice.

ansible-playbook ... --extra-vars '@my-vars.yaml' --extra-vars 'target_env=uat generate_report=true'

See documentation

Facts

Setup module

Basic example of running the setup module locally.

ansible -m setup all -i localhost, --connection=local

Sample Facts

Quick reference for some of the facts I commonly use.

Fact	Values (not exhaustive list)
ansible_os_family	'RedHat', 'Darwin', Debian'
ansible_distribution	'CentOS', 'MacOSX', 'Ubuntu'
ansible_distribution_major_version	'7'
ansible_distribution_version	'7.4.1804'
ansible_pkg_mgr	'yum', 'apt', 'homebrew'
ansible_system	'Linux', 'Darwin'
ansible_lsb	dict containing id (ansible_distribution), release (ansible_distribution_version) and others. Depends on lsb package being installed.
ansible_hostname
ansible_fqdn
ansible_env
ansible_dns.nameservers	List of name server IPs
ansible_dns.search	List of domains to search
ansible_domain

Access facts per host by just referencing the fact name as a variable. They are also available via {{ ansible_facts['fact_name'] }} or hostvars[inventory_hostname]['fact_name']. Note that ansible_facts is a subset of hostvars[inventory_hostname].

---
- hosts: localhost
  connection: local
  tasks:
    - name: print ansible_facts
      debug:
        var: ansible_facts

    - name: print all host facts
      debug:
        var: hostvars[inventory_hostname]