Data source vs resource difference in Terraform - Hands-On Comparison

Understanding Data Source vs Resource in Terraform

📖 Scenario: You are setting up cloud infrastructure using Terraform. You need to understand the difference between data sources and resources in Terraform to manage your infrastructure effectively.

🎯 Goal: Build a simple Terraform configuration that uses a data block to read existing information and a resource block to create new infrastructure.

📋 What You'll Learn

Create a data source block to fetch existing AWS AMI information

Create a resource block to launch an AWS EC2 instance using the fetched AMI

Use exact block names and attributes as specified

Follow Terraform best practices for configuration

💡 Why This Matters

🌍 Real World

Terraform data sources let you read existing cloud information, like AMIs, without creating them. Resources let you create and manage cloud infrastructure, like EC2 instances.

💼 Career

Understanding data sources vs resources is essential for cloud engineers and DevOps professionals to write efficient and reusable Terraform configurations.

1

Create a data source to fetch the latest Amazon Linux 2 AMI

Write a Terraform data block named aws_ami with the name amazon_linux that fetches the latest Amazon Linux 2 AMI using the filter name = "amzn2-ami-hvm-*-x86_64-gp2" and owners set to ["amazon"].

Terraform

# Your code here

Need a hint?

Use a data block with type aws_ami and name amazon_linux. Set most_recent to true. Use a filter block with name and values. Set owners to ["amazon"].

2

Create a resource to launch an EC2 instance using the fetched AMI

Add a Terraform resource block named aws_instance with the name example. Use the AMI ID from the data source data.aws_ami.amazon_linux.id and set the instance type to t2.micro.

Terraform

data "aws_ami" "amazon_linux" {
  most_recent = true
  filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
  }
  owners = ["amazon"]
}

# Your code here

Need a hint?

Use a resource block with type aws_instance and name example. Set ami to data.aws_ami.amazon_linux.id and instance_type to t2.micro.

3

Add a tag to the EC2 instance resource

Inside the aws_instance.example resource block, add a tags attribute with a map containing Name = "ExampleInstance".

Terraform

data "aws_ami" "amazon_linux" {
  most_recent = true
  filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
  }
  owners = ["amazon"]
}

resource "aws_instance" "example" {
  ami           = data.aws_ami.amazon_linux.id
  instance_type = "t2.micro"
  # Your code here
}

Need a hint?

Add a tags block inside the resource with Name = "ExampleInstance".

4

Add provider configuration for AWS

At the top of the file, add a provider block for aws with the region set to us-east-1.

Terraform

# Your code here

data "aws_ami" "amazon_linux" {
  most_recent = true
  filter {
    name   = "name"
    values = ["amzn2-ami-hvm-*-x86_64-gp2"]
  }
  owners = ["amazon"]
}

resource "aws_instance" "example" {
  ami           = data.aws_ami.amazon_linux.id
  instance_type = "t2.micro"
  tags = {
    Name = "ExampleInstance"
  }
}

Need a hint?

Add a provider block for aws with region = "us-east-1" at the top of the file.