From Terraform to K8s: A Practical End-to-End DevOps CI/CD Roadmap (IaC & GitOps)

From Terraform to Kubernetes: A Master Guide to the Complete Roadmap for Building Modern Infrastructure

If you're a developer or junior DevOps engineer just getting started in the cloud, you've probably run into these two keywords countless times: "build infrastructure with Terraform" and "deploy applications with Kubernetes." These two technologies are important enough to be called the twin pillars of modern infrastructure.

But here's the problem. When you learn them in isolation, it's easy to feel stuck—like you've collected a pile of fancy Lego bricks and then freeze in front of the question, "How do I actually connect these into a castle?"

This article is not a simple list of technologies. It is a master guide that lays out, at a glance, the overall principles and flow for building and operating modern enterprise-grade infrastructure from start to finish—from provisioning cloud resources, to deploying applications, to automating the entire process with a CI/CD pipeline.

🧱 Laying the Infrastructure Foundation: The Role of IaC (Infrastructure as Code) and Terraform

Imagine we're constructing a building. Before we can build, we need to prepare the ground, lay electrical and plumbing lines, and erect the building's skeleton (the frame). That "groundwork" and "framing" is what building infrastructure is, and managing that process as code is IaC.

Terraform is the leading IaC tool. Its core ideas are state management and a declarative approach.

• Declarative approach: You declare only the desired end state—"I need a VPC with this structure"—and Terraform compares that to the current state, calculates the diff, and applies only the necessary changes (the Plan).
• State file: Terraform records "the actual current shape of the infrastructure I created" in the terraform.tfstate file. That state file is how you can tell, among hundreds of resources, which already exist and which are missing.

💡 Practical tip: When you use Terraform, you configure a Provider so it can access resources from a cloud vendor (AWS, Azure, etc.). Think of the Provider as a "cloud API interpreter."

🚀 The Standard for Application Deployment: Container Orchestration and Kubernetes

Once the infrastructure is ready, you need to run real services on top of it. That's where containers come in. A container packages the application together with every dependency it needs to run, which fundamentally eliminates the "it works on my laptop but not on the server" problem.

A container by itself, though, is just a single container. Real services are made of dozens or hundreds of containers, and you need a management system that can start them reliably, restart them automatically on failure, and scale them when traffic spikes. That is container orchestration, and the standard is Kubernetes (K8s).

Kubernetes does the following:

1. Auto-scaling: Automatically adjusts the number of Pods based on traffic.
2. Self-healing: If a container dies, it immediately replaces it with a new one.
3. Service discovery: Manages network addresses so containers can find each other.

What's the Difference Between IaC and K8s? (Role Separation)

These two technologies solve problems at different layers. Understanding that difference clearly is the most important thing.

🔗 Combining the Two Technologies: A GitOps-Based CI/CD Pipeline Strategy

Beyond understanding each technology on its own, the automated workflow that connects them is the real DevOps skill. The key concept here is GitOps.

GitOps means declaring the entire desired state of applications and infrastructure as code in a Git repository (the Source of Truth), then having the cluster continuously sync itself to that Git state.

Overall architecture flow (Conceptual Flow):

graph TD
    A[개발자 코드 커밋] --> B{Git Repository};
    B --> C[CI Pipeline (Jenkins/GitHub Actions)];
    C --> D{Artifact 생성 (Docker Image)};
    D --> E[IaC 실행 (Terraform Plan/Apply)];
    E --> F[클라우드 리소스 준비 (VPC, EKS Cluster)];
    F --> G[K8s Manifest 업데이트 (Helm Chart/YAML)];
    G --> H[CD Pipeline (ArgoCD/Flux)];
    H --> I[K8s Cluster에 배포 및 동기화];

Example of a real workflow:

1. Prepare infrastructure (Terraform): First, deploy the EKS cluster itself with Terraform.
   Bash복사

   # 1. 필요한 리소스 정의 및 계획 수립
   terraform init
   terraform plan -out=tfplan
   
   # 2. 계획에 따라 실제 클라우드 리소스 생성/수정
   terraform apply tfplan

2. Deploy applications (K8s/GitOps): Once the cluster is ready, commit the application's deployment definition (Deployment YAML) to Git. A tool like ArgoCD detects that commit and performs operations similar to kubectl apply so the cluster's actual state matches Git.

📚 Key Concepts Recap and Learning Roadmap

Here are a few core terms from this guide.

✅ Five key terms

1. Idempotency: Performing the same operation multiple times always produces the same result. IaC follows this principle, so running the same code repeatedly does not tangle your infrastructure.
2. Declarative: You specify only what you want, not how. (e.g., "I need 3 web servers" $\rightarrow$ K8s keeps 3 running)
3. Provider: The plugin Terraform uses to talk to a specific cloud (AWS, GCP, etc.).
4. GitOps: An operating model that treats Git as the single source of truth for infrastructure and applications, and automatically syncs the system from Git changes.
5. State File: A snapshot of the infrastructure Terraform currently manages. If this file is corrupted, infrastructure management can break badly.

✍️ Practitioner advice: In the early learning stage, many people get stuck on the sequence "create K8s with Terraform, then deploy apps with K8s." In practice the most stable order is first spin up a cloud-managed K8s cluster (EKS/AKS) with Terraform $\rightarrow$ then install a GitOps tool (ArgoCD) on top of it to manage K8s. The infrastructure and the orchestration tooling itself should also be managed as code.

🗺️ Completing Your DevOps Roadmap

The end goal of this guide is not "mastering individual tools," but building an automated end-to-end flow. Reset your learning goals in this order:

1. Level 1 (Foundation): Practice deploying the minimum cloud resources (VPC, Subnet) as code with Terraform.
2. Level 2 (Execution): Understand K8s basics (Pod, Deployment, Service) and successfully do a manual deploy with kubectl.
3. Level 3 (Connection): Deploy the K8s cluster itself with Terraform, install a GitOps tool (ArgoCD, etc.), and build a full pipeline so applications deploy from Git commits alone.

Follow this roadmap and you will build the skills of a system designer, not just a user.

References: Official docs

The primary sources for the behavior, configuration, and errors covered in this article are the official docs below. Check them for version-specific options and exact behavior.

• Terraform official documentation

Frequently Asked Questions (FAQ)

Q. Which should I go deep on first, Terraform or Kubernetes? A. If your understanding of cloud environments is still thin, start by establishing the foundation (VPC, IAM) with Terraform. K8s is an application layer that runs on top of that foundation.

Q. If I use GitOps, do I no longer need CI/CD tools (Jenkins, etc.)? A. It does not fully replace them. The cleanest split is: CI tools handle build and artifact creation (Docker Image); GitOps tools (ArgoCD, etc.) handle deploy and sync.

Q. Is it a good idea to manage IaC and K8s manifests in the same place? A. Yes—strongly recommended. Putting all infrastructure definitions and application definitions in one Git repository (monorepo) is the GitOps philosophy, and it is the most efficient from a manageability standpoint.