Ansible troubleshooting - VARIABLE IS NOT DEFINED! ansible_hostname

Root cause analysis when the variable is not misspelled or not defined using the ansible_hostname internal variable and gather_facts boolean.

March 9, 2022

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#ansible #troubleshooting #variable #undefined #error #fatal #ansible-fact #gather_facts

Today we’re going to talk about Ansible troubleshooting, specifically about VARIABLE IS NOT DEFINED! Message. Most of the time the root cause is a misspelled variable or a variable really not defined. This use case is special about the ansible_hostname internal variable. I’m Luca Berton and welcome to today’s episode of Ansible Pilot.

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The best way of talking about Ansible troubleshooting is to jump in a live demo to show you practically the VARIABLE IS NOT DEFINED! and how to solve it!

error code

---
- name: hostname demo
  hosts: all
  gather_facts: false
  tasks:
    - name: print hostname
      ansible.builtin.debug:
        var: ansible_hostname

error execution

ansible-pilot $ ansible-playbook -i virtualmachines/demo/inventory troubleshooting/variablenotdefined_error.yml
PLAY [hostname demo] ******************************************************************************
TASK [print hostname] *****************************************************************************
ok: [demo.example.com] => {
"ansible_hostname": "VARIABLE IS NOT DEFINED!"
}
PLAY RECAP ****************************************************************************************
demo.example.com           : ok=1    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
ansible-pilot $

fix code

---
- name: hostname demo
  hosts: all
  gather_facts: true
  tasks:
    - name: print hostname
      ansible.builtin.debug:
        var: ansible_hostname

fix execution

ansible-pilot $ ansible-playbook -i virtualmachines/demo/inventory troubleshooting/variablenotdefined_fix.yml
PLAY [hostname demo] ******************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [print hostname] *****************************************************************************
ok: [demo.example.com] => {
    "ansible_hostname": "demo"
}
PLAY RECAP ****************************************************************************************
demo.example.com           : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
ansible-pilot $

code with ❤️ in GitHub

Recap

Now you know better how to troubleshoot the Ansible VARIABLE IS NOT DEFINED! message. Subscribe to the YouTube channel, Medium, and Website, X (formerly Twitter) to not miss the next episode of the Ansible Pilot.