Terraform: "Backend initialization required, please run terraform init"

Terraform: "Backend initialization required, please run terraform init"

What you are seeing

Error: Backend initialization required, please run "terraform init"

Reason: Unset backend "s3"
...

The .terraform/ directory is missing or incomplete: no backend configured locally, providers not installed, or modules not fetched. Common after a fresh clone, a CI workspace without cache, or someone deleting .terraform.

First response

1. Run terraform init. That is the fix in the common case.
2. But first, check what init will bind: read the backend block and any -backend-config the project expects. Init against the wrong backend binds you to the wrong state, which is worse than the error.
3. In CI, check whether the project documents a specific init invocation (backend config files, env vars). Repos that need init -backend-config=backends/prod.hcl will fail or misbehave with bare init.

Rules for agents

1. .terraform/ is disposable; the state file is not. Deleting .terraform and re-running init is safe. Touching the state file is not.
2. If init now asks to migrate state (-migrate-state), stop. The backend config differs from what was initialized before. Back up state first (terraform state pull > backup.json) and understand the change before answering yes.
3. Never commit .terraform/ to git. It is local installation cache. The lock file is committed; the installation directory is not.
4. If init fails on provider installation (network, registry), that is a separate problem from backend init. Fix them in order: backend first, then providers.

terraform init initializes backends, installs providers and modules; backend config changes require -reconfigure or -migrate-state. Verified against live init docs 2026-09-26. Verified against live docs 2026-09-26.