Multi-container Pods concept in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of Multi-container Pods

What is the main reason to use multiple containers inside a single Kubernetes Pod?

A To run tightly coupled containers that share resources and need to communicate closely

B To run completely independent applications that do not share any resources

C To increase the number of Pods running on a node without resource sharing

D To separate containers by namespaces for security isolation

💡 Hint

Think about containers that need to work together closely and share storage or network.

Multi-container Pods are designed to run containers that are tightly coupled and share the same network and storage. They communicate via localhost and share volumes.

💻 Command Output

intermediate

Output of Pod with Multiple Containers

Given this Pod YAML with two containers, what will be the output of kubectl get pods mypod -o jsonpath='{.spec.containers[*].name}'?

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  - name: app
    image: busybox
    command: ['sh', '-c', 'echo Hello from app']
  - name: sidecar
    image: busybox
    command: ['sh', '-c', 'echo Hello from sidecar']

A mypod app sidecar

B app sidecar

C app

D sidecar

💡 Hint

The command lists container names inside the Pod spec.

The jsonpath expression extracts all container names from the Pod spec, so it lists both 'app' and 'sidecar'.

❓ Configuration

advanced

Sharing Storage Between Containers in a Pod

Which volume configuration allows two containers in the same Pod to share files?

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: shared-pod
spec:
  containers:
  - name: container1
    image: busybox
    volumeMounts:
    - name: shared-data
      mountPath: /data
  - name: container2
    image: busybox
    volumeMounts:
    - name: shared-data
      mountPath: /data
  volumes:

A

  - name: shared-data
    emptyDir: {}

B

  - name: shared-data
    hostPath:
      path: /tmp/shared

C

  - name: shared-data
    configMap:
      name: shared-config

D

  - name: shared-data
    persistentVolumeClaim:
      claimName: pvc1

💡 Hint

Look for a volume type that creates a temporary directory shared in Pod lifetime.

emptyDir creates a temporary directory shared between containers in the same Pod, perfect for sharing files.

❓ Troubleshoot

advanced

Why Containers in a Pod Cannot Communicate

You have a Pod with two containers, but one container cannot reach the other on localhost. What is the most likely cause?

A Containers are in the same Pod but use different ports

B Containers are in the same Pod but use different volume mounts

C Containers are in the same Pod but have different images

D Containers are in different Pods, so they do not share the network namespace

💡 Hint

Remember that containers in the same Pod share network, but different Pods do not.

Containers in the same Pod share the network namespace and can communicate via localhost. If they are in different Pods, they cannot use localhost to communicate.

🔀 Workflow

expert

Order of Steps to Deploy a Multi-container Pod

Arrange the steps in the correct order to deploy a multi-container Pod and verify both containers are running.

A 2,1,3,4

B 1,3,2,4

C 1,2,3,4

D 1,2,4,3

💡 Hint

Think about writing config first, then applying it, then checking status, then logs.

You first write the YAML, then apply it to create the Pod, check if Pod is running, then check logs of each container.