Passing Variables to Ansible Playbook: A Quick Guide

How to pass or override an Ansible Playbook variable from the command line in plaintext, JSON, or YAML. It is very useful to combine some script, automation, or shell variables. For example, the fruit variable is defined as “banana” and changed to “apple” or “raspberry”.

Introduction

In today’s episode of Ansible Pilot, we’ll delve into the practical aspect of passing variables to Ansible Playbooks via the command line. This can be a powerful and flexible way to customize your playbook execution based on dynamic inputs. I’m Luca Berton, and let’s jump right into the world of Ansible extra variables.

Understanding Ansible Extra Variables

Ansible extra variables provide a means to pass values to your playbook from the command line. This flexibility is particularly valuable when you need to integrate Ansible into existing automation scripts or workflows. Extra variables can be specified in various formats, and today, we’ll explore a few options.

Command Line Syntax

The command line parameter for passing extra variables is --extra-vars, followed by the variable-value pair. Here are some examples:

--extra-vars "fruit=apple"
--extra-vars '{"fruit":"apple"}'
--extra-vars "@file.json"
--extra-vars "@file.yml"

Real-Life Example

Let’s illustrate this concept with a real-life example. Consider the following Ansible Playbook:

example.yml

---
- name: Extra variable demo
  hosts: all
  vars:
    fruit: "banana"
  task:
    - name: Print message
      ansible.builtin.debug:
        msg: "fruit is {{ fruit }}"

In this playbook, we have a variable named fruit with a default value of "banana." The playbook then prints a message using the value of this variable.

Executing Without Extra Variables

If we run the playbook without any extra variables, it uses the default value:

$ ansible-playbook -i inventory --extra-vars="fruit=apple" example.yml
PLAY [Extra variable demo] ************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [Print message] *****************************************************************************
ok: [demo.example.com] => {
    "msg": "fruit is apple"
}
PLAY RECAP ****************************************************************************************
demo.example.com           : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Executing With a Plain Extra Variable

Now, let’s provide a plain extra variable:

$ ansible-playbook -i inventory --extra-vars="fruit=apple" example.yml
PLAY [Extra variable demo] ************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [Print message] *****************************************************************************
ok: [demo.example.com] => {
    "msg": "fruit is apple"
}
PLAY RECAP ****************************************************************************************
demo.example.com           : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Executing With a JSON Extra Variable

Lastly, let’s use a JSON-formatted extra variable:

$ ansible-playbook -i inventory --extra-vars='{"fruit":"raspberry"}' example.yml
PLAY [Extra variable demo] ************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [Print message] *****************************************************************************
ok: [demo.example.com] => {
    "msg": "fruit is raspberry"
}
PLAY RECAP ****************************************************************************************
demo.example.com           : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Conclusion

In summary, passing extra variables to an Ansible Playbook through the command line is a straightforward process. Whether you choose a plain variable, a JSON-formatted one, or even reference a file, Ansible provides the flexibility to cater to your specific needs. This capability opens up endless possibilities for dynamic playbook executions, making your automation workflows even more powerful.