Bootstrapping Terraform

This solves a 🐓 and 🥚 problem in new AWS accounts (or for AWS accounts that have never used Terraform): How do you Terraform the remote state bucket? It takes the approach of keeping a local statefile in the repo that only manages these resources:

AWS Account Alias for the AWS account
S3 bucket for remote state file (using the TrussWorks s3-private-bucket module)
S3 bucket for storing state bucket access logs (using the TrussWorks logs module)
DynamoDB table for state locking and consistency checking

If the AWS account you are using already has a Terraform state bucket and locking table, this may not be the right tool for you.

Terraform Versions

Terraform 0.13. Pin module version to latest. Submit pull-requests to master branch.

Terraform 0.12. Pin module version to latest. Submit pull-requests to terraform012 branch.

Usage for bootstrapping

module "bootstrap" {
  source = "trussworks/bootstrap/aws"

  region        = "us-west-2"
  account_alias = "<ORG>-<NAME>"
}

Requirements

Name	Version
terraform	~> 0.13.0
aws	~> 3.0

Providers

Name	Version
aws	~> 3.0

Inputs

Name	Description	Type	Default	Required
account_alias	The desired AWS account alias.	`string`	n/a	yes
bucket_purpose	Name to identify the bucket's purpose	`string`	`"tf-state"`	no
log_name	Log name (for backwards compatibility this can be modified to logs)	`string`	`"log"`	no
log_retention	Log retention of access logs of state bucket.	`number`	`90`	no
region	AWS region.	`string`	n/a	yes

Outputs

Name	Description
dynamodb_table	The name of the dynamo db table
logging_bucket	The logging_bucket name
state_bucket	The state_bucket name

Bootstrapping

Create a new directory where your Terraform config will live. For example, it could live in a directory like terraform/account-alias/bootstrap.

If your aws commands run via aws-vault and you are using root credentials, you'll need to set the --no-session flag so the IAM operations can run without being MFA'd. If you're using the Truss aws-vault-wrapper you can set the AWS_VAULT_NO_SESSION environment variable. If you don't do this you'll receive an InvalidClientTokenId error.

If you are running your aws commands via aws-vault and are using a role assumption, you will want to run this script without AWS_VAULT_NO_SESSION. The role assumption between different profiles requires session behavior. Additionally, this script will attempt to run aws s3 ls before checking for bucket existence so that you can create a session token that may require an MFA handshake.

Set up your bootstrap/main.tf file to look like the example above. Don't forget to include a providers.tf file that looks like this:

provider "aws" {
  version = "~> 2.70.0"
  region  = local.region
}

Then run this like any other terraform module:

terraform init && terraform plan
# Review output of plan
terraform apply

The account alias will be configured (if not set), the resources will be created, and a state file will be generated. Commit the state file and the terraform code. Push those changes to your repo.

Subsequent changes

The bootstrap script should only be used for the initial setup. If you need to make any changes to the Terraform code (e.g. adding capacity to DynamoDB), follow your typical development processes for the code changes. Remember to commit the statefile after you apply the changes!

Using the backend

After provisioning the S3 bucket and the DynamoDB table, you need to tell Terraform that it exists and to use it. You do so by defining a backend. You can create a file called terraform.tf in your directory's root.

terraform {
  required_version = "~> 0.12"

  backend "s3" {
    bucket         = "bucket-name"
    key            = "path-to/terraform.tfstate"
    dynamodb_table = "terraform-state-lock"
    region         = "region"
    encrypt        = "true"
  }
}

bucket exists in the generated $tfvars_file from the bootstrap script's execution. Region also exists in that file or you passed it in the initial execution of the bootstrap script. The key is the path to the terraform.tfstate from the execution of the bootstrap script.

Upgrade Path

Pre-module releast to v0.1.1

To update from the pre-module release code that cloned this repo to the module release you'll need to do a few things:

Remove files that are no longer needed:

rm -f README.md bootstrap terraform.tfvars variables.tf versions.tf

Modify the main.tf to look like this:

locals {
  region = "us-west-2"
}

module "bootstrap" {
  source  = "trussworks/bootstrap/aws"
  version = "~> 0.1.1"

  account_alias = "<ORG>-<NAME>"
  region        = local.region
}

Modify the providers.tf to look like this:

provider "aws" {
  version = "~> 2.70.0"
  region  = local.region
}

Re-initialize the module and then get the terraform plan:

terraform init
terraform plan

Import the AWS account alias and then move the terraform state to the new namespaces.

terraform import module.bootstrap.aws_iam_account_alias.alias trussworks-cgilmer
terraform state mv aws_dynamodb_table.terraform_state_lock module.bootstrap.aws_dynamodb_table.terraform_state_lock
terraform state mv module.terraform_state_bucket.aws_s3_bucket.private_bucket module.bootstrap.module.terraform_state_bucket.aws_s3_bucket.private_bucket
terraform state mv module.terraform_state_bucket.aws_s3_bucket_analytics_configuration.private_analytics_config[0] module.bootstrap.module.terraform_state_bucket.aws_s3_bucket_analytics_configuration.private_analytics_config[0]
terraform state mv module.terraform_state_bucket.aws_s3_bucket_public_access_block.public_access_block module.bootstrap.module.terraform_state_bucket.aws_s3_bucket_public_access_block.public_access_block
terraform state mv module.terraform_state_bucket_logs.aws_s3_bucket.aws_logs module.bootstrap.module.terraform_state_bucket_logs.aws_s3_bucket.aws_logs
terraform state mv module.terraform_state_bucket_logs.aws_s3_bucket_public_access_block.public_access_block[0] module.bootstrap.module.terraform_state_bucket_logs.aws_s3_bucket_public_access_block.public_access_block[0]

Verify the changes result in no modification to the terraform plan:

terraform plan

Output should look like this if you are successful:

No changes. Infrastructure is up-to-date.

This means that Terraform did not detect any differences between your
configuration and real physical resources that exist. As a result, no
actions need to be performed.

Finally, commit your code and create a PR.

git checkout -b update_bootstrap_for_<ORG>_<NAME>
git commit -am"Update the bootstrap stack to use the bootstrap terraform module"

moosh3/terraform-aws-bootstrap