If you missed out on our previous session you can catch-up here. This week, we took a dive into Terraform and what makes it special.
A Comprehensive Deep Dive Into Terraform
In today’s cloud-driven world, engineers are moving away from manual provisioning and embracing automation at every layer of infrastructure. At the center of this revolution stands Terraform, one of the most powerful Infrastructure-as-Code (IaC) tools ever created. Terraform enables engineers to design, build, and manage infrastructure using code ensuring environments are consistent, repeatable, scalable, and automated.
This article provides a complete, beginner-friendly yet deep dive into Terraform:
What Terraform is
How the CLI works
Understanding Terraform State
Terraform’s core concepts and language
Real examples
A deeper dive into its architecture and workflow
If you want to step into DevOps, Cloud Engineering, or SRE Terraform is a skill you should master.
1. What Exactly Is Terraform?
Terraform is an open-source IaC tool created by HashiCorp. It lets you define your entire infrastructure using a simple, declarative language called HCL (HashiCorp Configuration Language).
Instead of clicking buttons on AWS, Azure, or GCP dashboards, you write code that describes the infrastructure, then Terraform creates it for you.
Example
Instead of manually creating an AWS EC2 instance through the console, you can write:
resource "aws_instance" "web" {
ami = "ami-12345"
instance_type = "t2.micro"
}
Then run:
terraform apply
Terraform reads the code → talks to AWS → creates the server.
Key Benefits
✔️ Infrastructure consistency
✔️ Faster deployments
✔️ Version-controlled infrastructure
✔️ Automated changes
✔️ Works across multiple clouds
✔️ Predictable workflows
Terraform doesn’t just build infrastructure it models complex architectures in a clean, human-readable way.
2. Terraform CLI (Command-Line Interface)
The Terraform CLI is how engineers interact with Terraform. It’s simple, consistent, and predictable.
Here are the most essential commands:
terraform init
Initializes your project, downloads providers, sets up plugins.
Think of it as: “Preparing the environment.”
terraform plan
Shows what Terraform wants to create, modify, or destroy.
Think of this as a preview or dry run.
terraform apply
Actually builds the infrastructure.
Once you confirm, Terraform makes everything real.
terraform destroy
Tears everything down.
Useful when testing, learning, or cleaning up environments.
terraform fmt
Formats your Terraform code automatically.
terraform validate
Checks your configuration for errors.
These commands form the backbone of Terraform usage every engineer uses them daily.
3. Terraform State (One of the Most Important Concepts)
Terraform manages infrastructure using a state file (terraform.tfstate).
This file is the single source of truth about what Terraform has created.
Why Is State Important?
Terraform compares:
What you want (your code)
What exists (state file)
Then it decides what changes to make.
Example
If your code says:
"Create 1 server,"
and your state file already has that server,
Terraform will do nothing.
If your code says:
"Create 3 servers,"
Terraform checks the state and adds 2 more.
Types of State Storage
Local State – default, saved on your machine
Remote State – stored in S3, GCS, Azure Blob, Terraform Cloud
(recommended for teams)
Real-World Example
In an AWS project, storing state in S3 ensures:
Multiple engineers can collaborate
The state is backed up
Changes are tracked securely
You avoid conflicting infrastructure changes
State files are the backbone of Terraform automation. Without state, Terraform wouldn’t know what to update.
4. Terraform Language & Core Terms
Terraform uses HCL, a clean, easy-to-read declarative language.
Below are the most important building blocks.
4.1 Providers
Providers allow Terraform to talk to cloud platforms.
Examples:
aws
google
azure
digitalocean
docker
A provider acts like a plugin that knows how to create resources in that platform.
provider "aws" {
region = "us-east-1"
}
4.2 Resources
Resources are the actual things Terraform creates:
servers
buckets
networks
containers
firewalls
Example:
resource "aws_s3_bucket" "logs" {
bucket = "my-log-bucket"
}
4.3 Variables
Variables make your Terraform reusable.
variable "region" {
default = "us-east-1"
}
4.4 Outputs
Outputs display results after deployment.
output "public_ip" {
value = aws_instance.web.public_ip
}
4.5 Modules
Modules are reusable Terraform packages.
Example: A module that sets up:
VPC
Subnets
Routing
Security groups
Modules allow you to reuse architecture patterns across projects essential for scaling infrastructure.
5. Deep Dive Into Terraform (How Terraform Actually Works)
Terraform runs in a four-step lifecycle every time you apply changes:
5.1 Initialization
Terraform downloads providers and ensures your workspace is ready.
5.2 Dependency Graph
Terraform automatically builds a graph of resources.
Example:
If you create:
VPC
Subnets
EC2 inside subnet
Terraform knows:
- Create VPC
- Then subnets
- Then EC2 instance
It figures out the order, you don’t tell it.
5.3 Execution Plan
Terraform compares:
your desired infrastructure (your code)
your current infrastructure (state file)
Then shows what it will change.
5.4 Apply
Terraform then:
creates new resources
modifies existing ones
deletes unused ones
All changes are recorded in the state file.
Real-World Example: Terraform in a Company
For instance, if a company wants to deploy:
3 AWS EC2 instances
1 RDS database
1 load balancer
1 S3 bucket
In the old days, this could take hours manually.
With Terraform:
Write the configuration once
Commit it to Git
Run terraform apply
In seconds, everything is deployed.
If the team wants to scale EC2 from 3 → 6:
Change a number in code
Apply again
Terraform automatically adds 3 more servers without breaking anything.
This is why big companies like Uber, Spotify, Coinbase, Airbnb, and Stripe use Terraform heavily.
Terraform revolutionizes how infrastructure is managed. It shifts teams from manual, error-prone tasks to automated, repeatable, scalable workflows.
Learning Terraform opens doors to roles in DevOps, SRE, Platform Engineering, Cloud Architecture, and Automation.
Understanding the CLI, state, providers, resources, modules, and deeper Terraform processes gives every beginner the power to build production-grade infrastructure with confidence.
Terraform is truly the language of modern cloud engineering.
I’m Ikoh Sylva, a passionate cloud computing enthusiast with hands-on experience in AWS. I’m documenting my cloud journey from a beginner’s perspective, aiming to inspire others along the way.
If you find my content helpful, please like and follow my posts, and consider sharing this article with anyone starting their own cloud journey.
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