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Ansible Variable Precedence
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ansible-variable-precedence.md

Ansible Variable Precedence

Here is the order of precedence from least to greatest (the last listed variables override all other variables):

  1. command line values (for example, -u my_user, these are not variables)
  2. role defaults (defined in role/defaults/main.yml) [1]
  3. inventory file or script group vars [2]
  4. inventory group_vars/all [3]
  5. playbook group_vars/all [3]
  6. inventory group_vars/* [3]
  7. playbook group_vars/* [3]
  8. inventory file or script host vars [2]
  9. inventory host_vars/* [3]
  10. playbook host_vars/* [3]
  11. host facts / cached set_facts [4]
  12. play vars
  13. play vars_prompt
  14. play vars_files
  15. role vars (defined in role/vars/main.yml)
  16. block vars (only for tasks in block)
  17. task vars (only for the task)
  18. include_vars
  19. set_facts / registered vars
  20. role (and include_role) params
  21. include params
  22. extra vars (for example, -e "user=my_user")(always win precedence)

In general, Ansible gives precedence to variables that were defined more recently, more actively, and with more explicit scope. Variables in the defaults folder inside a role are easily overridden. Anything in the vars directory of the role overrides previous versions of that variable in the namespace. Host and/or inventory variables override role defaults, but explicit includes such as the vars directory or an include_vars task override inventory variables.

Ansible merges different variables set in inventory so that more specific settings override more generic settings. For example, ansible_ssh_user specified as a group_var is overridden by ansible_user specified as a host_var.

[1] Variables defined in inventory file or provided by dynamic inventory.

[2] Includes vars added by ‘vars plugins’ as well as host_vars and group_vars which are added by the default vars plugin shipped with Ansible.

[3] When created with set_facts’s cacheable option, variables have the high precedence in the play, but are the same as a host facts precedence when they come from the cache.

[4] Within any section, redefining a var overrides the previous instance. If multiple groups have the same variable, the last one loaded wins. If you define a variable twice in a play’s vars: section, the second one wins.

Source

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