4. Intermediate on Terraform Basics on AWS Training

4.1. Versions

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Finish the Data Sources exercise and copy the directory:

mkdir -p $LAB_ROOT/intermediate/
cp -r $LAB_ROOT/basics/data_sources $LAB_ROOT/intermediate/versions
cd $LAB_ROOT/intermediate/versions

Step 4.1.1: Create versions.tf

Create a new file named versions.tf and add the following content:

terraform {
 required_version = "= 1.11.2"

 required_providers {
 random = {
 source = "hashicorp/random"
 version = "= 3.7.1"
 }
 local = {
 source = "hashicorp/local"
 version = "= 2.5.2"
 }
 }
}

Pin the required_version to the Terraform version you are using localy!

Explanation

With multiple engineers working on the same infrastructure code base, it is inevitable to have different versions of the Terraform CLI installed.

4.2. Count / Loops

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Create a new directory for this exercise:

mkdir -p $LAB_ROOT/intermediate/count_loops
cd $LAB_ROOT/intermediate/count_loops

Optional: Create empty files:

touch {main,elvis,multiple,outputs}.tf

Step 4.2.1: Conditional resource

By adding the identifier count to a resource, you can either make the resource conditional or create multiple instances.

Create a new file named elvis.tf in your working directory and paste the following:

locals {
 create_password = false
}

resource "random_password" "optional_password" {
 count = local.create_password ? 1 : 0
 length = 16
}

output "optional_password" {
 sensitive = true
 value = local.create_password ? random_password.optional_password.0.result : null
}

Explanation

The count identifier is (ab)used to create 0 instances of random_password. In case multiple instances exist, the resource turns into an array and has to be referenced using the .0 index.

4.3. Backend State

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Create a new directory for this exercise:

mkdir -p $LAB_ROOT/intermediate/backend_state
cd $LAB_ROOT/intermediate/backend_state

Optional: Create empty files:

touch main.tf

Step 4.3.1: Define a backend

Create a new file named main.tf and add the following content:

terraform {
 backend "local" {
 path = "foobar.tfstate"
 }
}

resource "random_password" "super_secret" {
 length = 16
}

Run the commands

terraform init
terraform apply

After the apply run:

ls -al

Now you should see a local file named foobar.tfstate containing the Terraform state.

Step 4.3.2: List all managed resources

Terraform has builtin commands to interact with the state.

4.4. Config Files

Mon, 01 Jan 0001 00:00:00 +0000

Preparation

Create a new directory for this exercise:

mkdir -p $LAB_ROOT/intermediate/multi_env
cd $LAB_ROOT/intermediate/multi_env

Optional: Create empty files:

touch {main,variables,outputs}.tf

Step 4.4.1: Define variable and output

Create a new file named variables.tf and add the following content:

variable "environment" {}

Create a new file named outputs.tf and add the following content:

output "current_env" {
 value = var.environment
}

Create a new file named main.tf and add the following content:

terraform {
 backend "local" {}
}

Explanation

The backend of type local is declared but missing the path argument; this is a so-called “partial configuration”. The missing argument will be added via a config file.