Kubernetes 101: Understanding Pods, Services, and Deployments

Kubernetes (K8s) is the industry standard for container orchestration. It automates deploying, scaling, and managing containerized applications across clusters of machines.

Core Concepts

Pods

A Pod is the smallest deployable unit in Kubernetes. It wraps one or more containers that share networking and storage.

yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
    - name: nginx
      image: nginx:1.25-alpine
      ports:
        - containerPort: 80

Deployments

A Deployment manages a set of identical Pods and handles rolling updates and rollbacks.

yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.25-alpine
          ports:
            - containerPort: 80
          resources:
            requests:
              cpu: "100m"
              memory: "128Mi"
            limits:
              cpu: "250m"
              memory: "256Mi"

Services

A Service provides stable networking for a set of Pods. Types include:

ClusterIP (default) — internal cluster access only
NodePort — exposes on each node's IP at a static port
LoadBalancer — provisions an external load balancer (cloud)

yaml

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  type: LoadBalancer
  selector:
    app: nginx
  ports:
    - port: 80
      targetPort: 80

Key kubectl Commands

bash

# Apply a manifest
kubectl apply -f deployment.yaml

# Get resources
kubectl get pods
kubectl get deployments
kubectl get services

# Describe a resource for details
kubectl describe pod nginx-pod

# View logs
kubectl logs -f deployment/nginx-deployment

# Scale a deployment
kubectl scale deployment nginx-deployment --replicas=5

# Delete resources
kubectl delete -f deployment.yaml

Namespaces

Namespaces isolate resources within a cluster. Use them to separate environments:

bash

kubectl create namespace staging
kubectl apply -f deployment.yaml -n staging
kubectl get pods -n staging

ConfigMaps and Secrets

Store configuration outside your containers:

yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  DATABASE_HOST: "postgres.default.svc.cluster.local"
  LOG_LEVEL: "info"

Health Checks

Always define liveness and readiness probes:

yaml

livenessProbe:
  httpGet:
    path: /healthz
    port: 8080
  initialDelaySeconds: 10
  periodSeconds: 15
readinessProbe:
  httpGet:
    path: /ready
    port: 8080
  initialDelaySeconds: 5
  periodSeconds: 10

Next Steps

Once comfortable with these primitives, explore Ingress controllers for HTTP routing, Helm for packaging, and Horizontal Pod Autoscaler for dynamic scaling.

Kubernetes 101: Understanding Pods, Services, and Deployments

Kubernetes 101: Understanding Pods, Services, and Deployments

Core Concepts

Pods

Deployments

Services

Key kubectl Commands

Namespaces

ConfigMaps and Secrets

Health Checks

Next Steps

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