AWS S3 Backend Terraform Module

A Terraform module for creating an Amazon S3 bucket and DynamoDB table for storing Terraform state.

Overview

From the Terraform documentation on S3 backends...

Stores the state as a given key in a given bucket on Amazon S3. This backend also supports state locking and consistency checking via DynamoDB, which can be enabled by setting the dynamodb_table field to an existing DynamoDB table name.

Usage

terraform {
  backend "s3" {
    bucket         = "<s3_bucket>"
    key            = "<path/to/key>"
    region         = "us-east-1"
    dynamodb_table = "<dynamodb_table>"
  }
}

Chicken and Egg Problem

Where does one store the Terraform state of the infrastructure for storing Terraform state? Answer: locally. Before using the Amazon S3 bucket and DynamoDB table created by this module to store its own state, you must first store state on the local filesystem. Thereafter, state can be stored using the S3 backend.

Step 1: Initialize Terraform using local backend

$ terraform init
Initializing modules...
...

Initializing the backend...
...

Terraform has been successfully initialized!

Step 2: Apply state

$ terraform apply
...

Apply complete! Resources: 2 added, 0 changed, 0 destroyed.

Step 3: Reconfigure Terraform with S3 backend

terraform {
  backend "s3" {
    bucket         = "<s3_bucket>"
    key            = "<path/to/key>"
    region         = "us-east-1"
    dynamodb_table = "<dynamodb_table>"
  }
}

$ terraform init -reconfigure
Initializing modules...

Initializing the backend...
Do you want to copy existing state to the new backend?
  Pre-existing state was found while migrating the previous "local" backend to the
  newly configured "s3" backend. No existing state was found in the newly
  configured "s3" backend. Do you want to copy this state to the new "s3"
  backend? Enter "yes" to copy and "no" to start with an empty state.

  Enter a value: yes

Terraform Module Documentation

Resources

Name	Type
aws_dynamodb_table.dynamodb_table	resource
aws_s3_bucket.s3_bucket	resource

Inputs

Name	Description	Type	Default	Required
dynamodb_table	Name of the DynamoDB table to store Terraform state lock.	string	n/a	yes
s3_bucket	Name of the Amazon S3 bucket to store Terraform state.	string	n/a	yes

Outputs

Name	Description
dynamodb_table	The name of the DynamoDB table
s3_bucket	The name of the S3 bucket