Exercise 2: Namespaces and Resources

Objective

Learn how to organize and manage resources using namespaces, and understand resource management concepts like resource quotas and labels.

Prerequisites

• Completed Exercise 1: Basic Kubernetes
• Understanding of Pods, Deployments, and Services

Exercise: Organize Resources with Namespaces

Step 1: Create Multiple Namespaces

Namespaces help you organize resources and apply policies. Let's create separate namespaces for different environments.

YAML Version: Create namespaces.yaml:

apiVersion: v1
kind: Namespace
metadata:
  name: development
---
apiVersion: v1
kind: Namespace
metadata:
  name: staging
---
apiVersion: v1
kind: Namespace
metadata:
  name: production

Apply:

kubectl apply -f namespaces.yaml

Verify:

kubectl get namespaces

Step 2: Deploy Applications to Different Namespaces

Let's deploy the same application to different namespaces to see how namespaces provide isolation.

YAML Version: Create deployment-dev.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-app
  namespace: development
  labels:
    app: web-app
    environment: development
spec:
  replicas: 2
  selector:
    matchLabels:
      app: web-app
  template:
    metadata:
      labels:
        app: web-app
        environment: development
    spec:
      containers:
        - name: nginx
          image: nginx:latest
          ports:
            - containerPort: 80

YAML Version: Create deployment-staging.yaml:

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

Apply:

kubectl apply -f deployment-dev.yaml
kubectl apply -f deployment-staging.yaml

Step 3: Use Labels and Selectors

Labels help you organize and select resources. Let's see how they work.

List pods by label:

# All web-app pods
kubectl get pods -l app=web-app --all-namespaces

# Only development pods
kubectl get pods -l environment=development --all-namespaces

# Combined selector
kubectl get pods -l app=web-app,environment=development -n development

Step 4: Resource Queries Across Namespaces

See how namespaces isolate resources:

# Pods in specific namespace
kubectl get pods -n development
kubectl get pods -n staging

# All pods across all namespaces
kubectl get pods --all-namespaces

# Deployments in all namespaces
kubectl get deployments --all-namespaces

Verification

Verify namespace isolation:

# Check deployments in each namespace
kubectl get deployments -n development
kubectl get deployments -n staging

# Verify pods are isolated
kubectl get pods -n development
kubectl get pods -n staging

# Check that services in one namespace can't see pods in another
kubectl get endpoints -n development
kubectl get endpoints -n staging

Understanding What Happened

• Namespaces: Provide logical separation and isolation
• Labels: Key-value pairs for organizing and selecting resources
• Selectors: Used to match resources by labels
• Isolation: Resources in different namespaces are isolated from each other

Cleanup

Remove all resources:

kubectl delete namespace development
kubectl delete namespace staging
kubectl delete namespace production

Next Steps

→ Exercise 3: ConfigMaps and Secrets

Additional Practice

1. Create a namespace with a specific label: kubectl create namespace test --dry-run=client -o yaml | kubectl label --local -f - team=backend -o yaml
2. List all namespaces with a label: kubectl get namespaces -l team=backend
3. Try to access a pod from another namespace (it won't work without proper service configuration)