Terraform
Terraform: How to Get Environment Variables
Learn how to securely access and utilize environment variables within your Terraform configurations for dynamic and configurable infrastructure deployments.
Learn how to securely access and utilize environment variables within your Terraform configurations for dynamic and configurable infrastructure deployments.
This guide explains how to effectively use environment variables in your Terraform projects to create flexible and configurable infrastructure deployments. You'll learn how to define and access environment variables within your Terraform configurations, follow best practices for naming and handling sensitive information, and explore alternative methods for passing variables to Terraform. Additionally, we'll touch upon prioritizing variable definitions from different sources and introduce tools for managing environments in more complex scenarios.
Define environment variables: Start by defining the environment variables you want to use in your Terraform configuration. You can do this directly in your terminal or through a script. For example, to set an environment variable named TF_VAR_DATABASE_NAME, you would use:
export TF_VAR_DATABASE_NAME="my-database"Access variables in Terraform: In your Terraform configuration files (e.g., main.tf), you can access these environment variables using the var data source. For instance, to retrieve the value of TF_VAR_DATABASE_NAME, you would use:
resource "aws_rds_cluster" "example" {
# ... other configurations ...
database_name = data.terraform_remote_state.vpc.outputs.database_name
}Variable naming convention: It's a common practice to prefix your environment variables with TF_VAR_ to clearly indicate that they are intended for Terraform. This helps avoid conflicts with other environment variables.
Sensitive information: Avoid storing sensitive data like passwords or API keys directly in environment variables. Instead, consider using secure storage mechanisms like HashiCorp Vault or AWS Secrets Manager and fetch these secrets within your Terraform code.
Alternative to environment variables: While environment variables offer a straightforward way to pass values to Terraform, you can also utilize other methods like:
-var flag..tfvars files and load them during Terraform execution.Prioritize explicit definitions: If a variable is defined both as an environment variable and within a variable file or as a command-line argument, Terraform will prioritize the most explicit definition. The order of precedence is:
.tfvars filesLeverage tools for managing environments: For more complex scenarios with multiple environments (e.g., development, staging, production), consider using tools like Terragrunt or Terraform Cloud to streamline environment management and variable handling.
This code demonstrates using environment variables in Terraform to configure an AWS EC2 instance. It defines environment variables for AWS region and instance type, then uses them in a Terraform configuration file to provision an EC2 instance with those settings. The code includes setting up the provider, defining the instance with variables, and fetching the latest Ubuntu AMI. Finally, it shows how to run the Terraform code. The example emphasizes using environment variables for simple configurations and suggests secure storage options for sensitive information and advanced tools for complex scenarios.
This example demonstrates how to use environment variables to configure an AWS EC2 instance.
1. Define Environment Variables:
export TF_VAR_AWS_REGION="us-west-2"
export TF_VAR_INSTANCE_TYPE="t2.micro"2. Terraform Configuration (main.tf):
terraform {
required_providers {
aws = {
source = "hashicorp/aws"
version = "~> 4.0"
}
}
}
provider "aws" {
region = var.aws_region
}
resource "aws_instance" "example" {
ami = data.aws_ami.ubuntu.id
instance_type = var.instance_type
tags = {
Name = "Example EC2 Instance"
}
}
data "aws_ami" "ubuntu" {
most_recent = true
filter {
name = "name"
values = ["ubuntu/images/hvm-ssd/ubuntu-focal-20.04-amd64-server-*"]
}
filter {
name = "virtualization-type"
values = ["hvm"]
}
owners = ["099720109477"] # Canonical
}
variable "aws_region" {
type = string
}
variable "instance_type" {
type = string
}Explanation:
TF_VAR_AWS_REGION and TF_VAR_INSTANCE_TYPE.var.aws_region and var.instance_type.aws_instance resource uses these variables to define the region and instance type.3. Running Terraform:
terraform init
terraform applyTerraform will use the values from the environment variables to provision the EC2 instance.
Note: This is a basic example. For sensitive information, consider using secure storage mechanisms like HashiCorp Vault or AWS Secrets Manager. For complex scenarios, explore tools like Terragrunt or Terraform Cloud for enhanced environment management.
terraform console and the var.<variable_name> syntax to inspect the values of your environment variables within a Terraform context. This helps in troubleshooting issues related to variable values..env files: Consider using a .env file (e.g., with the dotenv library) to manage environment variables, especially during development. This keeps your terminal cleaner and makes it easier to share environment configurations.validation block within your variable definitions to enforce constraints on the values that can be assigned to environment variables. This helps prevent unexpected input and ensures data integrity.These notes provide a more comprehensive understanding of using environment variables in Terraform, covering security, debugging, best practices, and alternative approaches.
This article provides a guide on effectively using environment variables within your Terraform projects.
Key takeaways:
export command. Prefix them with TF_VAR_ for clarity.var data source..tfvars)..tfvars files > environment variables).By following the principles and examples outlined in this article, you can leverage environment variables to make your Terraform configurations more adaptable and maintainable. Remember to prioritize security, especially when dealing with sensitive data, and explore advanced tools like Terragrunt or Terraform Cloud for managing complex, multi-environment deployments. By incorporating these practices, you can streamline your infrastructure provisioning process and create more robust and scalable infrastructure deployments.
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