3.3. Planning, Applying, and Destroying
💡 First Principle: These three commands are the reconciliation loop made executable — plan computes the diff, apply enacts it, destroy drives the diff toward "nothing" — so their behavior is entirely predictable once you think in terms of desired vs. current state.
Why care: This is the heart of the exam's heaviest objective. Questions probe the read-only nature of plan, the role of saved plan files, the approval behavior of apply, and what destroy does (and how to scope it).
The mental model: plan is the contractor's written estimate; apply is authorizing the work; destroy is demolition. The estimate changes nothing; authorization is the moment of commitment; demolition is the reverse operation.
⚠️ Common Misconception: Learners think a plan, once generated, is a static promise that apply will follow exactly. It is — but only if you save it. A bare terraform apply generates a fresh plan at apply time and could differ from an earlier plan if reality changed in between. Saved plan files are how you guarantee apply does exactly what you reviewed.
