Kubernetes basics review in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Kubernetes Pod Status Check

What is the output of the command kubectl get pods immediately after creating a Pod with an invalid image name?

Microservices

kubectl run invalid-pod --image=nonexistentimage12345 --restart=Never
kubectl get pods

A

NAME          READY   STATUS             RESTARTS   AGE
invalid-pod   0/1     ImagePullBackOff   0          10s

B

NAME          READY   STATUS    RESTARTS   AGE
invalid-pod   1/1     Running   0          10s

C Error from server (NotFound): pods "invalid-pod" not found

D

NAME          READY   STATUS    RESTARTS   AGE
invalid-pod   0/1     Completed 0          10s

💡 Hint

Think about what happens when Kubernetes cannot pull the container image.

When Kubernetes tries to start a Pod with a non-existent image, it fails to pull the image and the Pod status becomes 'ImagePullBackOff'.

🧠 Conceptual

intermediate

Kubernetes Service Types

Which Kubernetes Service type exposes the service on a cluster-internal IP only, making it reachable only within the cluster?

A ExternalName

B LoadBalancer

C NodePort

D ClusterIP

💡 Hint

Think about which service type does not expose ports outside the cluster.

ClusterIP service type exposes the service on an internal IP accessible only within the cluster.

❓ Troubleshoot

advanced

Debugging Kubernetes Deployment Rollout Failure

You deployed a new version of your app using a Deployment, but the rollout is stuck and pods are not becoming ready. Which kubectl command helps you see detailed rollout status and errors?

A kubectl describe deployment <deployment-name>

B kubectl rollout status deployment/<deployment-name>

C kubectl logs deployment/<deployment-name>

D kubectl get pods --watch

💡 Hint

Look for a command that specifically tracks rollout progress.

The command 'kubectl rollout status' shows the progress and any issues during a deployment rollout.

🔀 Workflow

advanced

Kubernetes ConfigMap Usage

You want to update a ConfigMap used by a running Pod without restarting the Pod. Which approach allows the Pod to see the updated ConfigMap data automatically?

A Mount the ConfigMap as a volume inside the Pod

B Pass ConfigMap data as environment variables to the Pod

C Use kubectl exec to manually update files inside the Pod

D Delete and recreate the Pod after updating the ConfigMap

💡 Hint

Think about how Kubernetes handles ConfigMap volumes and environment variables.

ConfigMaps mounted as volumes are updated automatically inside the Pod, while environment variables require Pod restart.

✅ Best Practice

expert

Kubernetes Resource Limits and Requests

What is the main reason to set both resource requests and limits for containers in a Kubernetes Pod?

A To guarantee the container gets exactly the requested resources at all times

B To ensure the container never uses more CPU or memory than requested

C To allow Kubernetes scheduler to place Pods efficiently and prevent resource overuse

D To automatically restart the Pod if it exceeds resource usage

💡 Hint

Consider how Kubernetes uses requests and limits differently for scheduling and runtime.

Requests help the scheduler decide where to place Pods, while limits prevent containers from using excessive resources at runtime.

Practice

1. What is a pod in Kubernetes?

easy

A. A command-line tool to manage Kubernetes

B. The smallest unit that runs one or more containers together

C. A configuration file format used in Kubernetes

D. A network policy to control traffic

Solution

1. Step 1: Understand Kubernetes resource types

   Kubernetes groups containers into pods to run them together on the same host.

2. Step 2: Identify the role of a pod

   A pod is the smallest deployable unit that can contain one or more containers sharing resources.

3. Final Answer:

   The smallest unit that runs one or more containers together -> Option B

4. Quick Check:

   Pod = smallest container group [OK]

Hint: Pods group containers; smallest deployable unit [OK]

Common Mistakes:

• Confusing pods with kubectl tool
• Thinking pods are config files
• Mixing pods with network policies

2. Which command correctly lists all pods in the default namespace?

easy

A. kubectl get pods

B. kubectl list pods

C. kubectl show pods

D. kubectl describe pods all

Solution

1. Step 1: Recall kubectl commands for listing resources

   The standard command to list pods is kubectl get pods.

2. Step 2: Check other options for correctness

   kubectl list pods and kubectl show pods are invalid commands; kubectl describe pods all is incorrect syntax.

3. Final Answer:

   kubectl get pods -> Option A

4. Quick Check:

   List pods = kubectl get pods [OK]

Hint: Use 'kubectl get pods' to list pods [OK]

Common Mistakes:

• Using 'list' or 'show' instead of 'get'
• Adding unnecessary arguments like 'all'
• Confusing describe with get

3. Given this YAML snippet for a pod:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
spec:
  containers:
  - name: myapp-container
    image: nginx:latest
    ports:
    - containerPort: 80

What will kubectl get pods myapp-pod show after creation?

medium

A. NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Completed 0 0s

B. Error: pod not found

C. NAME READY STATUS RESTARTS AGE
myapp-pod 0/1 Pending 0 0s

D. NAME READY STATUS RESTARTS AGE
myapp-pod 1/1 Running 0 0s

Solution

1. Step 1: Understand pod creation from YAML

   The YAML defines a pod with one container running nginx, exposing port 80.

2. Step 2: Predict pod status after creation

   Immediately after creation, the pod should be running with 1 container ready, so status is Running and READY is 1/1.

3. Final Answer:

   NAME READY STATUS RESTARTS AGE myapp-pod 1/1 Running 0 0s -> Option D

4. Quick Check:

   Pod created and running = READY 1/1 Running [OK]

Hint: New pod with valid image shows READY 1/1 Running [OK]

Common Mistakes:

• Expecting Pending status without reason
• Confusing Completed with Running
• Assuming pod not found immediately after creation

4. You run kubectl apply -f pod.yaml but get an error: "error: unable to recognize \"pod.yaml\": no matches for kind \"Pod\" in version \"v2\"". What is the likely fix?

medium

A. Delete the pod.yaml and recreate it

B. Rename the file to pod.yml

C. Change apiVersion from v2 to v1 in pod.yaml

D. Run the command with sudo

Solution

1. Step 1: Analyze the error message

   The error says no matches for kind "Pod" in version "v2", meaning the apiVersion is invalid.

2. Step 2: Correct the apiVersion in YAML

   The correct apiVersion for Pod is "v1", so changing from "v2" to "v1" fixes the issue.

3. Final Answer:

   Change apiVersion from v2 to v1 in pod.yaml -> Option C

4. Quick Check:

   apiVersion must be valid (v1 for Pod) [OK]

Hint: Check apiVersion spelling and value in YAML [OK]

Common Mistakes:

• Changing file extension instead of apiVersion
• Running with sudo unnecessarily
• Deleting file without fixing content

5. You want to update a running pod's container image from nginx:1.19 to nginx:1.21 without downtime. Which Kubernetes resource and method should you use?

hard

A. Create a Deployment and update its image with kubectl set image

B. Directly edit the pod with kubectl edit pod to change the image

C. Delete the pod and create a new one with the new image

D. Use kubectl scale pod to increase replicas

Solution

1. Step 1: Understand pod immutability and updates

   Pods are immutable; you cannot update container images directly on running pods without recreating them.

2. Step 2: Use Deployment for zero downtime updates

   Deployments manage pods and allow rolling updates to change images without downtime using kubectl set image.

3. Final Answer:

   Create a Deployment and update its image with kubectl set image -> Option A

4. Quick Check:

   Use Deployment + set image for smooth updates [OK]

Hint: Use Deployment and set image for zero downtime update [OK]

Common Mistakes:

• Trying to edit pod image directly
• Deleting pod causes downtime
• Scaling pod is invalid command