Pods and Deployments

A pod is one or more containers sharing a network and storage. Bare pods are not replaced if they die, so you almost always use a Deployment.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 3
  selector:
    matchLabels: { app: web }
  template:
    metadata:
      labels: { app: web }
    spec:
      containers:
        - name: web
          image: nginx:1.20
          ports: [{ containerPort: 80 }]

kubectl apply -f web.yaml
kubectl get pods -l app=web
kubectl set image deployment/web web=nginx:1.21
kubectl rollout status deployment/web
kubectl rollout undo deployment/web

The Deployment creates a ReplicaSet, which keeps three pods running. A rolling update replaces pods gradually, and rollout undo returns to the previous ReplicaSet. Generate YAML quickly with kubectl create deployment web --image=nginx:1.20 --dry-run=client -o yaml.