Terraform Basic.

1. What is Terraform? (In simple words)

Terraform is a tool to create and manage cloud infrastructure using code.

Instead of clicking in AWS console to create:

• EC2

• VPC

• Load Balancer

• S3

• RDS

You write code once, and Terraform creates everything automatically.

This approach is called Infrastructure as Code (IaC).

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2. Why Terraform is used in DevOps

In DevOps, we want:

Problem	Without Terraform	With Terraform
Create servers	Manual clicks	One command
Same setup in Dev & Prod	Different configs	Same code
Rollback infra	Hard	Easy
Infra tracking	No history	Git versioning
Team collaboration	Messy	Clean

Terraform makes infra:

• Repeatable

• Version-controlled

• Automated

• Fast

• Less error-prone

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3. When to use Terraform

Use Terraform when:

• You are working with cloud (AWS, Azure, GCP)

• You want same infra in Dev, QA, Prod

• You are doing CI/CD pipelines

• You want auto infra creation

• You want to avoid manual cloud setup

• You manage Kubernetes, servers, networking, storage

Do NOT use Terraform for:

• Application code deployment (use CI/CD tools)

• Small one-time manual setup (overkill)

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4. Where Terraform is used (Industry use cases)

Terraform is used in:

• Cloud infrastructure (AWS, Azure, GCP)

• Kubernetes cluster setup (EKS, AKS, GKE)

• Networking (VPC, Subnets, Security Groups)

• Load balancers

• Databases

• Auto scaling infra

• Multi-cloud setup

• Disaster recovery infra

• CI/CD pipelines

Used by companies like:
Netflix, Uber, Spotify, Swiggy, Zomato, startups, enterprises

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5. How Terraform works (Flow)

Terraform works in 5 simple steps:

1. Write code

2. Initialize Terraform

3. Preview changes

4. Apply infra

5. Destroy infra when needed

Command flow:

terraform init
terraform plan
terraform apply
terraform destroy

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6. Important Terraform Concepts (DevOps perspective)

a) Provider

Tells Terraform which cloud to use

Example: AWS

provider "aws" {
  region = "ap-south-1"
}

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b) Resource

Actual infra like EC2, S3, VPC

resource "aws_instance" "web" {
  ami           = "ami-0f58b397bc5c1f2e8"
  instance_type = "t2.micro"
}

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c) Variables

To avoid hardcoding values

variable "instance_type" {
  default = "t2.micro"
}

instance_type = var.instance_type

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d) Output

Show values after creation

output "public_ip" {
  value = aws_instance.web.public_ip
}

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e) State file

Terraform keeps infra info in terraform.tfstate

Used for:

• Tracking resources

• Updating infra

• Destroying infra

In industry, this is stored in S3 backend.

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f) Backend (Remote State)

terraform {
  backend "s3" {
    bucket = "my-terraform-state"
    key    = "prod/terraform.tfstate"
    region = "ap-south-1"
  }
}

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g) Modules

Reusable Terraform code

Used in companies to:

• Avoid duplicate code

• Follow standard infra templates

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7. Industry Standard Terraform Setup (Step by Step)

This is how real companies use Terraform:

Step 1: Create Git repo

infra-terraform/
  ├── modules/
  ├── envs/
  │   ├── dev/
  │   ├── qa/
  │   └── prod/

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Step 2: Setup Remote Backend (S3 + DynamoDB)

• S3 for state file

• DynamoDB for state locking

Why?

• Team collaboration

• Avoid state corruption

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Step 3: Create IAM User for Terraform

Permissions:

• EC2

• VPC

• S3

• RDS

• IAM (limited)

Never use root account.

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Step 4: Write Terraform Code

provider "aws" {
  region = "ap-south-1"
}

resource "aws_instance" "app" {
  ami           = "ami-0f58b397bc5c1f2e8"
  instance_type = "t2.micro"
  tags = {
    Name = "dev-app-server"
  }
}

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Step 5: Connect Terraform with CI/CD (GitHub Actions / GitLab CI)

Example flow:

1. Developer pushes Terraform code

2. Pipeline runs:

   • terraform init

   • terraform plan

3. On approval:

   • terraform apply

This is how infra changes go to production safely.

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8. Real Example (Create EC2 in AWS)

provider "aws" {
  region = "ap-south-1"
}

resource "aws_instance" "myserver" {
  ami           = "ami-0f58b397bc5c1f2e8"
  instance_type = "t2.micro"

  tags = {
    Name = "terraform-server"
  }
}

Run:

terraform init
terraform plan
terraform apply

Boom. EC2 created.

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9. Advantages of Terraform

• Works with all clouds

• Infra as Code

• Version control

• Fast infra setup

• Same infra everywhere

• Easy rollback

• Team collaboration

• Automation friendly

• Less manual errors

• Supports CI/CD

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10. Terraform vs Cloud Console (Interview Point)

Feature	Cloud Console	Terraform
Automation	❌	✅
Repeatability	❌	✅
Version control	❌	✅
Team collaboration	❌	✅
Rollback	❌	✅
Multi-cloud	❌	✅

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11. Terraform Interview Questions (Very Important)

You should be ready to answer:

• What is Terraform and IaC?

• What is terraform state file?

• Difference between terraform plan and apply

• What is provider?

• What is module?

• How to manage secrets in Terraform?

• How to use Terraform in CI/CD?

• How to manage multiple environments?

• How to avoid infra deletion by mistake?

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12. How to learn Terraform fast (DevOps roadmap)

Week 1:

• Basics: provider, resource, init, plan, apply

Week 2:

• Variables, outputs, state, backend

Week 3:

• Modules, remote state, CI/CD integration

Week 4:

• Project: Create VPC + EC2 + Load balancer