# Correct way to use fail module and negative conditionals

**URL:** <https://forum.ansible.com/t/correct-way-to-use-fail-module-and-negative-conditionals/20050>\
**Category:** Ansible Project\
**Created:** [December 20, 2015, 4:18am UTC](https://forum.ansible.com/t/correct-way-to-use-fail-module-and-negative-conditionals/20050 "2015-12-20T04:18:52Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![CyberCyber](https://avatars.discourse-cdn.com/v4/letter/c/a88e4f/32.png) [@CyberCyber](https://forum.ansible.com/u/CyberCyber)\
**Post date:** [December 20, 2015, 4:18am UTC](https://forum.ansible.com/t/correct-way-to-use-fail-module-and-negative-conditionals/20050/1 "2015-12-20T04:18:52Z")

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I am trying to use the fail module at the very beginning of my playbook to check if the target server is a specific distribution and version. This way I can stop the playbook from running early on before any making any chances.

playbook:

`

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<div class="post-metadata">

**Author:** ![CyberCyber](https://avatars.discourse-cdn.com/v4/letter/c/a88e4f/32.png) [@CyberCyber](https://forum.ansible.com/u/CyberCyber)\
**Post date:** [December 23, 2015, 9:44pm UTC](https://forum.ansible.com/t/correct-way-to-use-fail-module-and-negative-conditionals/20050/2 "2015-12-23T21:44:34Z")

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anyone able to help ?

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**Author:** ![Josh\_Smift1](https://avatars.discourse-cdn.com/v4/letter/j/bcef8e/32.png) [@Josh\_Smift1](https://forum.ansible.com/u/Josh_Smift1)\
**Post date:** [December 23, 2015, 9:59pm UTC](https://forum.ansible.com/t/correct-way-to-use-fail-module-and-negative-conditionals/20050/3 "2015-12-23T21:59:49Z")

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> &nbsp;&nbsp;&nbsp;&nbsp;- name: check if target server is CentOS 6 or Ubuntu 14  
> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;fail: msg='unsupported platform detected!'  
> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;when: (ansible\_distribution != "CentOS" and  
> ansible\_distribution\_major\_version != "6") or (ansible\_distribution !=  
> "Ubuntu" and ansible\_distribution\_major\_version != "14")

This logic seems wrong to me. With

&nbsp;&nbsp;&nbsp;"msg": "distro is CentOS and version is 6"

then your when turns into

&nbsp;&nbsp;when: (False and False) or (True and True)

aka

&nbsp;&nbsp;when: False or True

aka True. Right?

I think you want something more like

&nbsp;&nbsp;when: NOT (CentOS 6 or Ubuntu 14)

than like

&nbsp;&nbsp;when: (not CentOS 6) or (not Ubuntu 14)

Because you're always going to be not one of those things -- you need to  
negate the whole or.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-Josh (jbs@care.com)

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<div class="post-metadata">

**Author:** ![CyberCyber](https://avatars.discourse-cdn.com/v4/letter/c/a88e4f/32.png) [@CyberCyber](https://forum.ansible.com/u/CyberCyber)\
**Post date:** [January 6, 2016, 12:53am UTC](https://forum.ansible.com/t/correct-way-to-use-fail-module-and-negative-conditionals/20050/4 "2016-01-06T00:53:52Z")

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Thanks for clarifying that for me Josh.

What I did was create a variable that contains the supported distributions and have my when condition check against it:

`  
vars:  
supported\_distros: “{{ ansible\_distribution }} {{ ansible\_distribution\_major\_version }}”

tasks:

- name: check if server is running a supported distro  
fail: msg=‘Unsupported platform!’  
when: platform not in [“Ubuntu 14”,“CentOS 6”]  
`

That did the tricks!