Ansible Magic Variables Reference

Q: What Are Magic Variables?

Ansible automatically defines magic variables (also called special variables) that you can use in any playbook. These provide information about hosts, groups, the play environment, and execution context.

What Are Magic Variables?

Ansible automatically defines magic variables (also called special variables) that you can use in any playbook. These provide information about hosts, groups, the play environment, and execution context.

Host Variables

inventory_hostname

The name of the current host as defined in inventory:

- name: Show current host
  ansible.builtin.debug:
    msg: "Running on {{ inventory_hostname }}"

inventory_hostname_short

The first part of inventory_hostname (before the first dot):

# If inventory_hostname = web1.example.com
- ansible.builtin.debug:
    msg: "Short name: {{ inventory_hostname_short }}"
    # Output: "Short name: web1"

ansible_host

The actual IP/hostname Ansible connects to:

- ansible.builtin.debug:
    msg: "Connecting to {{ ansible_host }}"

ansible_facts

Dictionary of all gathered facts about the current host:

- name: Show OS family
  ansible.builtin.debug:
    msg: "OS: {{ ansible_facts['os_family'] }}"

- name: Show memory
  ansible.builtin.debug:
    msg: "Total RAM: {{ ansible_facts['memtotal_mb'] }} MB"

- name: Show IP address
  ansible.builtin.debug:
    msg: "IP: {{ ansible_facts['default_ipv4']['address'] }}"

Common facts:

ansible_facts['os_family'] — Debian, RedHat, etc.
ansible_facts['distribution'] — Ubuntu, CentOS, etc.
ansible_facts['memtotal_mb'] (also ansible_memtotal_mb)
ansible_facts['processor_vcpus']
ansible_facts['default_ipv4']['address']

Group Variables

groups

Dictionary of all groups and their hosts:

- name: List all web servers
  ansible.builtin.debug:
    msg: "Web servers: {{ groups['webservers'] }}"

- name: List all hosts
  ansible.builtin.debug:
    msg: "All hosts: {{ groups['all'] }}"

group_names

List of groups the current host belongs to:

- name: Show my groups
  ansible.builtin.debug:
    msg: "{{ inventory_hostname }} is in groups: {{ group_names }}"

- name: Run only for webservers
  ansible.builtin.apt:
    name: nginx
    state: present
  when: "'webservers' in group_names"

hostvars

Access variables from any host:

- name: Get DB server IP
  ansible.builtin.debug:
    msg: "DB IP: {{ hostvars['db1']['ansible_host'] }}"

- name: Get another host's fact
  ansible.builtin.debug:
    msg: "DB memory: {{ hostvars['db1']['ansible_memtotal_mb'] }}"

Play and Execution Variables

playbook_dir

The directory where the playbook file lives:

- name: Show playbook location
  ansible.builtin.debug:
    msg: "Playbook is at: {{ playbook_dir }}"

- name: Copy file relative to playbook
  ansible.builtin.copy:
    src: "{{ playbook_dir }}/files/config.yml"
    dest: /opt/app/config.yml

role_path

The directory of the current role:

# Inside a role's tasks/main.yml
- name: Copy template from role
  ansible.builtin.template:
    src: "{{ role_path }}/templates/app.conf.j2"
    dest: /etc/app/app.conf

ansible_play_hosts

List of hosts active in the current play:

- name: Show active hosts
  ansible.builtin.debug:
    msg: "Active hosts: {{ ansible_play_hosts }}"

- name: Count active hosts
  ansible.builtin.debug:
    msg: "Deploying to {{ ansible_play_hosts | length }} hosts"

ansible_play_batch

Hosts in the current batch (when using serial):

- name: Show current batch
  ansible.builtin.debug:
    msg: "Batch: {{ ansible_play_batch }}"

play_hosts (deprecated)

Use ansible_play_hosts instead.

Execution Context Variables

Variable	Description
`ansible_version`	Ansible version info dict
`ansible_check_mode`	`true` if running in check mode (`--check`)
`ansible_diff_mode`	`true` if running with `--diff`
`ansible_verbosity`	Verbosity level (0-4)
`ansible_run_tags`	Tags provided via `--tags`
`ansible_skip_tags`	Tags provided via `--skip-tags`

- name: Skip destructive task in check mode
  ansible.builtin.command: /opt/app/migrate.sh
  when: not ansible_check_mode

- name: Extra detail in verbose mode
  ansible.builtin.debug:
    msg: "Detailed info: {{ hostvars[inventory_hostname] }}"
  when: ansible_verbosity >= 2

Task Result Variables

After register:

- name: Run command
  ansible.builtin.command: whoami
  register: result

- name: Use result
  ansible.builtin.debug:
    msg: |
      stdout: {{ result.stdout }}
      rc: {{ result.rc }}
      changed: {{ result.changed }}

Quick Reference Table

Variable	Type	Description
`inventory_hostname`	string	Current host name from inventory
`inventory_hostname_short`	string	Short hostname (before first dot)
`ansible_host`	string	Connection address
`ansible_facts`	dict	Gathered facts
`groups`	dict	All groups → host lists
`group_names`	list	Groups current host belongs to
`hostvars`	dict	Variables for all hosts
`playbook_dir`	string	Playbook directory path
`role_path`	string	Current role directory
`ansible_play_hosts`	list	Active hosts in play
`ansible_play_batch`	list	Current serial batch
`ansible_check_mode`	bool	Check mode active
`ansible_version`	dict	Ansible version info

Ansible Tutorial for Beginners — Complete getting started guide
How to Install Ansible — Installation on all platforms
Ansible Training — Courses and certifications
Ansible Dry Run — Test playbooks safely
Ansible Facts — Gather system info
Ansible Vault — Encrypt secrets
Ansible Error Handling — Handle failures

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