📜 Writing Kubernetes YAML Manifests - A Beginner-Friendly Guide 🚀

Welcome to Day 22 of your Kubernetes journey! 🌟 Today, we’ll explore Kubernetes YAML Manifests, which are used to define and deploy applications inside a Kubernetes cluster.

Think of Kubernetes YAML files as blueprints 🏗️ that tell Kubernetes what to build and how to manage it—just like an architect’s design for a building. Let’s break it down step by step in a simple and structured way! 📑

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🛠️ What is a Kubernetes YAML Manifest?

A Kubernetes Manifest is a configuration file written in YAML (Yet Another Markup Language) that defines the desired state of a Kubernetes object. Instead of manually creating resources using commands, you write a YAML file and apply it to Kubernetes.

🔥 Why Use YAML in Kubernetes?

✅ Human-Readable – Easy to understand for both humans & machines 🧑‍💻
✅ Declarative – You describe what you want, and Kubernetes figures out how to do it 🚀
✅ Reusable & Portable – Easily share configurations with teams 🌎
✅ Version Controlled – Store YAML files in Git for collaboration & tracking 📜

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📄 Basic Structure of a Kubernetes YAML File

A Kubernetes YAML file typically follows this structure:

apiVersion: v1  # API version for the resource
kind: Pod       # Type of resource (Pod, Deployment, Service, etc.)
metadata:
  name: my-pod  # Name of the resource
spec:
  containers:
    - name: my-container
      image: nginx  # Docker image
      ports:
        - containerPort: 80

📌 Explanation:

• apiVersion: Specifies the API version for the Kubernetes object

• kind: Defines what type of resource this file creates (Pod, Deployment, Service, etc.)

• metadata: Contains resource details like its name & labels

• spec: The actual specification of the resource (like what container to run)

📌 Analogy:
Think of this as an online food order 🍕:

• apiVersion = The version of the food delivery system 📦

• kind = The type of order (pizza, burger, sushi) 🍣

• metadata = Customer details (name, address, phone) 📞

• spec = Order details (which food, how much, what toppings) 🍄

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🔹 Common Kubernetes Resources & Their YAML Manifests

1️⃣ Pod Manifest – The Smallest Deployable Unit

A Pod is the basic unit in Kubernetes—it contains one or more containers that run your application.

apiVersion: v1
kind: Pod
metadata:
  name: web-pod
spec:
  containers:
    - name: web-container
      image: nginx
      ports:
        - containerPort: 80

📌 Analogy:
A Pod is like a food truck 🚛—it has everything needed inside (kitchen, ingredients, staff) and can be placed at any location (node) to serve customers (users).

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2️⃣ Deployment Manifest – Managing Multiple Pods

A Deployment ensures that a specific number of identical Pods are running at all times. If a Pod crashes, Kubernetes will restart it automatically.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-deployment
spec:
  replicas: 3  # Runs 3 replicas of the Pod
  selector:
    matchLabels:
      app: web-app
  template:
    metadata:
      labels:
        app: web-app
    spec:
      containers:
        - name: web-container
          image: nginx
          ports:
            - containerPort: 80

📌 Analogy:
A Deployment is like a restaurant chain 🍽️—if one branch (Pod) shuts down, another is ready to take over!

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3️⃣ Service Manifest – Exposing Pods to the Network

A Service provides a stable network endpoint for accessing a set of Pods. Without it, Pods would be unreachable from the outside world! 🌍

apiVersion: v1
kind: Service
metadata:
  name: web-service
spec:
  selector:
    app: web-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: ClusterIP  # Internal service within the cluster

📌 Analogy:
A Service is like a waiter 🧑‍🍳 in a restaurant—it ensures that customers (users) get the right food (requests go to the correct Pod).

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🚀 Additional Kubernetes Resources You Should Know

🗄 ConfigMap – Managing Configuration Separately

Instead of hardcoding configuration inside Pods, store it in a ConfigMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  database_url: "mysql://db-service:3306"

📌 Analogy:
A ConfigMap is like a menu card 📜 in a restaurant—you can change it anytime without modifying the kitchen setup (Pods).

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🔑 Secret – Storing Sensitive Information Securely

Secrets are like ConfigMaps but used for storing passwords, API keys, etc.

apiVersion: v1
kind: Secret
metadata:
  name: db-secret
type: Opaque
data:
  password: cGFzc3dvcmQ=  # Base64-encoded value

📌 Analogy:
A Secret is like a restaurant’s special recipe 🍲—only authorized chefs (services) should have access to it!

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✅ Best Practices for Writing Kubernetes YAML Manifests

📌 Follow these tips to avoid common pitfalls:

✔️ Use meaningful names for resources 📛
✔️ Keep YAML well-indented to avoid syntax errors 📏
✔️ Use labels & selectors for efficient resource management 🏷️
✔️ Avoid hardcoding values—use ConfigMaps & Secrets 🔑
✔️ Use Helm Charts 🎩 for complex applications
✔️ Store YAML files in Git for version control and rollback 🔄

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🎯 Summary – Key Takeaways

🔹 YAML Manifests define the desired state of Kubernetes objects
🔹 Pods are the smallest deployable units (like food trucks 🚛)
🔹 Deployments manage multiple Pods (like restaurant chains 🍽️)
🔹 Services expose Pods (like waiters serving food 🍜)
🔹 ConfigMaps & Secrets help separate configuration from code

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🏁 Next Steps: Try It Yourself!

💡 Hands-On Practice:
1️⃣ Create a Pod YAML and deploy it
2️⃣ Convert it into a Deployment for better scalability
3️⃣ Expose it using a Service

🚀 Experiment, break things, and learn!

Got questions? Drop them in the comments below! 🗨️💬