TFLAB29-moved Blocks: Refactoring Without Destroy or Recreate

moved Blocks: Refactoring Without Destroy/Recreate

🔧 Terraform Core ⭐ Intermediate moved from / to Refactoring

Scenario

You renamed a resource from aws_s3_bucket.data to aws_s3_bucket.app_data. Without a moved block, Terraform would destroy the old bucket and create a new one. The moved block tells Terraform "same resource, new name" — no destruction.

Your Objectives
  • Create a resource, apply it.
  • Rename the resource in code and add a moved block.
  • Run plan — observe "moved" instead of "destroy + create".
  • Understand moved blocks for module refactoring too.

Additional Context

moved blocks (Terraform 1.1+) are the declarative alternative to terraform state mv. They live in your code, are visible in version control, and work in CI/CD without manual CLI steps.

Step 1: Original config

terraform {
  required_version = ">= 1.5.0"
  required_providers {
    aws = { source = "hashicorp/aws", version = "~> 5.0" }
  }
}
provider "aws" { region = "us-east-1" }
data "aws_caller_identity" "current" {}

resource "aws_s3_bucket" "data" {
  bucket = "moved-demo-${data.aws_caller_identity.current.account_id}"
  tags   = { ManagedBy = "terraform" }
}

Step 2: Rename + moved block

# Renamed resource: "data" → "app_data"
resource "aws_s3_bucket" "app_data" {
  bucket = "moved-demo-${data.aws_caller_identity.current.account_id}"
  tags   = { ManagedBy = "terraform" }
}

# Tell Terraform: same resource, new name
moved {
  from = aws_s3_bucket.data
  to   = aws_s3_bucket.app_data
}

# For module moves:
# moved {
#   from = module.old_name
#   to   = module.new_name
# }

Workflow Commands

terraform init && terraform apply   # create the bucket

# Rename in code, add moved block, then:
terraform plan
# aws_s3_bucket.app_data has moved from aws_s3_bucket.data
# Plan: 0 to add, 0 to change, 0 to destroy.

terraform apply   # applies the move in state
terraform destroy
✓ Move Plan Output
# aws_s3_bucket.app_data has moved from aws_s3_bucket.data
Plan: 0 to add, 0 to change, 0 to destroy.

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