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1 — Resources and state

Folder: 01-basics/1-create-local-file/

A resource is something Terraform owns for its whole lifecycle. It creates it, notices when it drifts, and destroys it on terraform destroy. That ownership is recorded in the state file — Terraform's ledger mapping config addresses to real things.

The code

resource "local_file" "pet" {
  filename        = "/tmp/hello.txt"
  content         = "Hello! Let the terraform learning commence...."
  file_permission = "0700"
}

Run it

terraform init && terraform apply
cat /tmp/hello.txt
terraform state list     # local_file.pet — Terraform now has a record of it
terraform destroy        # the file is gone

The two experiments that matter

These two look similar and behave completely differently. Run both.

Delete the file, keep the state:

terraform apply
rm /tmp/hello.txt
terraform plan     # Terraform detects the drift and offers to recreate it

Terraform compares state against reality during the refresh step, sees the file is gone, and plans to recreate it. This is drift detection doing its job, not magic.

Delete the state, keep the file:

terraform apply
rm terraform.tfstate
terraform plan     # Terraform has no memory of the file and plans to create it fresh

Terraform has no idea the file exists. It will not go looking for it — there is no reconciliation pass that scans the world for things that might be yours. It plans a create, and on apply it silently clobbers the existing file.

That silent clobber is provider-specific and worth remembering. A cloud API usually protects you here: google_service_account rejects a duplicate account_id with an "already exists" error rather than overwriting. local_file has no such protection. Don't assume every provider fails safe — see State surgery.

Key takeaway

State is the only thing connecting your config to reality. Lose it and Terraform doesn't search for orphans, it just tries to create again. Adoption of an existing resource is always explicit — see terraform import.

Theory: §4 Resources and state · Quiz: Resources, state & drift · Next: Variables