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DevOps / Ansible Interview questions

Explain the internal working of Ansible's variable precedence resolution?

Internally, Ansible builds up a variable's final value by layering every source that defines it, in a fixed precedence order, so the value that "wins" is whichever source sits highest in that order, regardless of the order files happen to be read from disk.

flowchart TD A[Role defaults - lowest] --> B[Inventory vars] B --> C[Inventory group_vars / host_vars] C --> D[Playbook vars / vars_files] D --> E[Role vars] E --> F[Block / task vars] F --> G[Registered vars and facts] G --> H[Extra vars -e - highest] H --> I[Final resolved value used by the task]

As Ansible processes a playbook, it maintains an internal merged variable namespace per host; each layer above simply overwrites the same key if it's also defined at a lower layer, rather than merging values together (with the notable exception of hash/dictionary merging, which can be configured via hash_behaviour, though the default is still overwrite, not merge). Because -e extra vars sit at the very top, they always win regardless of what's set anywhere else in roles, inventory, or playbooks - this is deliberate, since it gives an operator a reliable way to force a value at runtime without needing to trace through every file that might otherwise define it.

By default, what happens when the same variable is defined at two different precedence layers?
What setting can change how dictionaries interact across precedence layers?

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