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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demo

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, Website, Twitter, and Substack to not miss the next episode of the Ansible Pilot.