📘 Terraform Series – Day 7

Variables & Outputs (Make Your Code Smart 🔥)

In real-world DevOps, writing flexible and reusable code is very important.
Today, we will learn how to use Variables and Outputs in Terraform to make our infrastructure clean, dynamic, and production-ready.

Till now, we were writing Terraform code…
but there was one problem 👇

👉 Everything was hardcoded

And in real DevOps, hardcoding = BIG mistake ❌

So today we fix that 💡

🧩 Step 1: The Real Problem

Imagine this:

instance_type = "t2.micro"

Looks simple… but 👇

❌ Want to upgrade instance? Change everywhere

❌ Want reuse? Not possible

❌ Working in team? Becomes messy

👉 Basically: Not scalable

💡 Step 2: The Smart Solution → Variables

Instead of fixing values in code, we use variables

Think like this:
👉 “Keep values separate, keep code clean”

✔ Why Variables?

• Change once → Apply everywhere

• Clean & readable code

• Reusable infrastructure

• Industry-level practice

📌 In short:
Variables = Flexibility + Clean Code + DevOps Standard

📄 Step 3: Create variables.tf

variable "ec2_instance_type" {
  default = "t2.micro"
  type    = string
}

variable "ec2_root_storage_size" {
  default = 10
  type    = number
}

variable "ec2_ami_id" {
  default = "ami-0cb91c7de36eed2cb"
  type    = string
}

🧠 Simple Understanding:

• variable → variable name

• default → default value

• type → data type

👉 Values are now separated from the main code ✅

🔗 Step 4: Use Variables in ec2.tf

Now the real magic 🔥

# Create Key Pair
resource "aws_key_pair" "my_key" {
  key_name   = "terra-key-aws"
  public_key = file("terra-key-aws.pub")
}


# Default VPC
resource "aws_default_vpc" "default" {}

# Security Group
resource "aws_security_group" "my_groups" {
  name        = "my-group"
  description = "Security group for EC2"
  vpc_id      = aws_default_vpc.default.id

  ingress {
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
    description = "Allow SSH"
  }

  ingress {
    from_port   = 80
    to_port     = 80
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
    description = "Allow HTTP"
  }

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
    description = "Allow all outbound"
  }

  tags = {
    Name = "automate-sg"
  }
}

# EC2 Instance
resource "aws_instance" "my_instance" {
  ami                    = var.ec2_ami_id
  instance_type          = var.ec2_instance_type
  key_name               = aws_key_pair.my_key.key_name
  vpc_security_group_ids = [aws_security_group.my_groups.id]

  root_block_device {
    volume_size = var.ec2_root_storage_size
    volume_type = "gp3"
  }

  tags = {
    Name = "terra-ec2"
  }
}

⚡ Important Line:

var.<variable_name>

👉 Example:

var.ec2_instance_type

🔄 Step 5: Real Power of Variables

Before:

instance_type = "t2.micro"

After:

default = "t3.micro"

✔ Change in one place

✔ Applied everywhere automatically

🔥 That’s the power

📤 Step 6: Now Let’s Talk About Outputs

Deployment is done… but now 👇

👉 How do you get EC2 Public IP?

😓 Problem

❌ You have to manually check AWS Console

💡 Solution → Outputs

Terraform will show it directly 🔥

📄 Step 7: Create outputs.tf

output "ec2_public_ip" {
  value = aws_instance.my_instance.public_ip
}

output "ec2_public_dns" {
  value = aws_instance.my_instance.public_dns
}

🧠 What Happens Now?

When you run:

terraform apply

👉 At the end, Terraform shows:

✔ Public IP

✔ Public DNS

Directly in terminal 🎯

👨‍💻 About the Author

“A complete Terraform series covering everything from fundamentals to advanced real-world infrastructure automation in a DevOps environment.”

📬 Let's Stay Connected

• 📧 Email: gujjarapurv181@gmail.com

• 🐙 GitHub: github.com/ApurvGujjar07

• 💼 LinkedIn: linkedin.com/in/apurv-gujjar