This assumes you have installed Ansible Tower and are familiar with the ansible-playbook command and facts. Variables can be created using vars or set_facts. In this example, set_facts is used to create a variable named "foo" with a value of "Hello World".

---
- hosts: all
  tasks:
    - set_facts: foo="Hello World"

debug can be used to print the variable, which will produce output like this.

TASK [debug]
ok: [server1.example.com] => {
    "msg": "Hello World"
}

Or, variables can be created on the command line and passed into the playbook, like this.

ansible-playbook playbook.yml -i inventory.yml --extra-vars "foo=Hello bar=World"

In this scenario, you would not define the variable in your playbook.yml file, but you would use the variable in your playbook.yml file.

---
- hosts: all
  tasks:
    - set_facts: var1="{{foo}}
    - set_facts: var1="{{bar}}

Global variables

By default, variables are isolated to only be accessible within a hosts. Here is now to create a variable that can be used in multiple hosts.

- hosts: all
  tasks:
    - set_fact: foo="Hello World"

- hosts: all
  tasks:
    -debug: msg="{{foo}}"

- hosts: web
  tasks:
    - debug: msg="{{foo}}"

Or, you can start like this, if you know the variable only needs to be used in certain hosts.

- hosts: web:db