Variables

Precedence

1. command line values (for example, -u my_user, these are not variables)
2. role defaults (as defined in Role directory structure) 1
3. inventory file or script group vars 2
4. inventory group_vars/all 3
5. playbook group_vars/all 3
6. inventory group_vars/* 3
7. playbook group_vars/* 3
8. inventory file or script host vars 2
9. inventory host_vars/* 3
10. playbook host_vars/* 3
11. host facts / cached set_facts 4
12. play vars
13. play vars_prompt
14. play vars_files
15. role vars (as defined in Role directory structure)
16. block vars (only for tasks in block)
17. task vars (only for the task)
18. include_vars
19. set_facts / registered vars
20. role (and include_role) params
21. include params
22. extra vars (for example, -e "user=my_user")(always win precedence)

group_vars

group_vars is a special folder to store variable for an Ansible Group.

You can specify: group_vars/group_name/some_name_file.yml. Ansible will then go and parse all the files from group_vars/group_name/*.(yml|json)

Example

Given the inventory file

app:
  hosts:
    app1: 
      ansible_host: 192.168.60.4
    app2: 
      ansible_host: 192.168.60.5

db:
  hosts:
    app3:
      ansible_host: 192.168.60.6

server:
  children:
    db:
    app:
  vars:
    ansible_user: vagrant
    ansible_ssh_private_key_file: ~/.vagrant.d/insecure_private_key

In here, the groups are app and db and server

We want to create variables for db

Create group_vars/db. Note again that ansible will parse all the *.yml files in here*.

Create proxy.yml

proxy_setting:
  http_proxy: localhost
  https_proxy: localhost

Create regions.yml

---
regions:
  available:
    - us-west
    - au-east
  active: au-east

Now we can use this variable in our yml file like {{ proxy_setting }} or {{ regions.available.active }}

Create a playbook variable-test.yml

- name: test the variables
  hosts: db
  tasks:
  - name: print variables out
    debug:
      msg: "regions: {{regions}} proxy: {{proxy_setting}}"

Run with:

ansible-playbook -i staging.yml variable-test.yml

ok: [app3] => {
    "msg": "regions: {'available': ['us-west', 'au-east'], 'active': 'au-east'} proxy: {'http_proxy': 'localhost', 'https_proxy': 'localhost'}"
}

Note

We can also declare our variable as json format. For example: group_vars/all/others.json

{
    "available_commands": ["help", "top", "ps"],
    "available_users": {
        "austin": {
            "is_admin": false
        },
        "david": {
            "is_admin": true
        }
    }
}

We can then parse this variable in anywhere, for example tasks:

- name: print json variables
  debug:
  msg: "available_commands: {{available_commands}} available_users: {{available_users}}"

will print out:

ok: [app3] => {
    "msg": "available_commands: ['help', 'top', 'ps'] available_users: {'austin': {'is_admin': False}, 'david': {'is_admin': True}}"
}

Or we can use it in another variable files (e.g group_vars/db/user.yml):

admin_user: "{{available_users["david"]}}"