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Lab 3.1 - Creating and Managing Pods

Objectives​

By the end of this lab, you will be able to:

  • Create Pods with YAML
  • Manage the Pod lifecycle
  • Use labels and selectors
  • Inspect Pods

Prerequisites​

  • Functioning Kubernetes cluster
  • kubectl installed and configured

Exercise 1: Create a Simple Pod​

Step 1: Create the YAML file​

Create pod-simple.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
    env: dev
spec:
  containers:
  - name: nginx
    image: nginx:1.20
    ports:
    - containerPort: 80

Step 2: Create the Pod​

kubectl apply -f pod-simple.yaml

Step 3: Verify​

# View the Pod
kubectl get pods

# Details
kubectl describe pod nginx-pod

# Logs
kubectl logs nginx-pod

Exercise 2: Pod with Environment Variables​

Create pod-env.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: env-pod
spec:
  containers:
  - name: busybox
    image: busybox
    command: ['sh', '-c', 'echo $MESSAGE && sleep 3600']
    env:
    - name: MESSAGE
      value: "Hello from Kubernetes!"

Apply and check the logs.

Exercise 3: Multi-Container Pod​

Create pod-multi.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: multi-pod
spec:
  containers:
  - name: nginx
    image: nginx:1.20
  - name: busybox
    image: busybox
    command: ['sh', '-c', 'while true; do echo $(date); sleep 5; done']

Test the communication between containers.

Exercise 4: Labels and Selectors​

Step 1: Create multiple Pods with labels​

kubectl run pod1 --image=nginx:1.20 --labels=app=web,env=prod
kubectl run pod2 --image=nginx:1.20 --labels=app=web,env=prod
kubectl run pod3 --image=nginx:1.20 --labels=app=api,env=dev

Step 2: Filter with labels​

# Pods with app=web
kubectl get pods -l app=web

# Pods with app=web AND env=prod
kubectl get pods -l app=web,env=prod

# Pods without env=dev
kubectl get pods -l 'env!=dev'

Exercise 5: Lifecycle​

Step 1: Observe the phases​

# Create a Pod
kubectl run test-pod --image=nginx:1.20

# Observe the phases
kubectl get pod test-pod -w

# View events
kubectl describe pod test-pod

Step 2: Test the restart​

Create a Pod that crashes:

apiVersion: v1
kind: Pod
metadata:
  name: crash-pod
spec:
  restartPolicy: Always
  containers:
  - name: busybox
    image: busybox
    command: ['sh', '-c', 'exit 1']

Observe the automatic restart.

Cleanup​

# Delete all created Pods
kubectl delete pod nginx-pod env-pod multi-pod pod1 pod2 pod3 test-pod crash-pod

Reflection Questions​

  1. What is the difference between a single-container and multi-container Pod?
  2. How do containers in a Pod communicate?
  3. Why use labels?
  4. What happens if a container crashes?

Next Steps​

Lab 3.2: Deploying with ReplicaSets
Chapter 3.5: ReplicaSets

Lab created: December 2024