Creating Kubernetes Deployments

Full Deployment Example

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 3
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
        - name: nginx
          image: nginx:1.27
          ports:
            - containerPort: 80

Key Fields to Notice

replicas

How many pod instances you want.

selector.matchLabels

This tells the Deployment which pods belong to it.

template

This is the pod blueprint used for each replica.

Apply the Deployment

kubectl apply -f deployment.yaml

Inspect the Deployment

kubectl get deployment
kubectl rollout status deployment/web
kubectl get rs
kubectl get pods -l app=web

Scale the Deployment

kubectl scale deployment web --replicas=5

Kubernetes then updates the ReplicaSet and creates more pods.

Why Label Selectors Matter

The selector must match the labels on the pod template. If they do not match, the Deployment cannot manage the pods correctly.

Mental Model

A Deployment is not the pod itself. It is the recipe and control logic for keeping the right number of matching pods alive.