KCNA Practice Questions 2 — 50 Questions

Question 1

A user creates a Service of type ClusterIP with a selector matching pods labeled 'app: myapp'. However, a pod named 'myapp-pod' with label 'app: myapp' is not receiving traffic. What is a possible reason?

Accepted Answer

The pod's readiness probe is failing. Services target pods by selector; if the pod is not ready due to failing readiness probes, it won't receive traffic.

Answer

The Service type should be NodePort

Answer

The pod is in a different namespace

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The pod's container port is not defined

Question 2

Which TWO statements about containers are true compared to virtual machines? (Select TWO.)

Accepted Answer

Containers are more lightweight and start faster than VMs. Containers share the host OS kernel, making them lightweight and fast to start, and they are more portable because they bundle only the application and its dependencies.

Answer

Containers include a full guest operating system

Answer

Containers provide stronger isolation than VMs

Answer

Containers require a hypervisor to run

Question 3

Which of the following is a key benefit of container orchestration compared to running containers manually?

Accepted Answer

Automatic scaling and self-healing. Container orchestration provides automated scaling, self-healing, and declarative management, which are not available when running containers manually.

Answer

Containers use less memory

Answer

Orchestration eliminates the need for container images

Answer

Containers run faster when orchestrated

Question 4

An application requires that a pod must not be scheduled on the same node as another pod from the same Deployment. Which configuration should be used?

Accepted Answer

Pod anti-affinity with requiredDuringSchedulingIgnoredDuringExecution and topologyKey: kubernetes.io/hostname. Pod anti-affinity with a requiredDuringSchedulingIgnoredDuringExecution rule and a topologyKey of 'kubernetes.io/hostname' ensures that pods are not co-located on the same node.

Answer

Node affinity with requiredDuringSchedulingIgnoredDuringExecution

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Pod affinity with a preferredDuringSchedulingIgnoredDuringExecution

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Taints and tolerations

Question 5

You are designing a microservices application that requires each service to be independently deployable and scalable. The services communicate over HTTP and need service discovery. Which orchestration feature BEST addresses the need for service discovery?

Accepted Answer

Kubernetes Service. Option C is correct. Kubernetes Services provide stable IP addresses and DNS names that enable service discovery within the cluster. Option A refers to scaling, not discovery. Option B is about configuration, not discovery. Option D is a storage abstraction.

Answer

Horizontal Pod Autoscaler

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ConfigMap

Answer

PersistentVolume

Question 6

Which THREE are benefits of using container orchestration platforms like Kubernetes?

Accepted Answer

High availability through automatic container restart and replication. Options A, B, and D are correct. Orchestration provides high availability (A), scaling (B), and self-healing (D). Option C is false — orchestration adds complexity, not simplicity. Option E is false — manual intervention can be reduced, but orchestration does not eliminate the need for management.

Answer

Simplified application development by eliminating the need for code changes

Answer

Elimination of the need for monitoring and logging

Question 7

What is the primary difference between a container and a virtual machine (VM)?

Accepted Answer

Containers share the host OS kernel, whereas VMs each have their own guest OS. Containers share the host OS kernel and run as isolated processes, while VMs include a full guest OS and run on hypervisor-managed virtual hardware.

Answer

Containers are slower to start than VMs

Answer

Containers require a hypervisor to run

Answer

Containers virtualize hardware, while VMs virtualize the operating system

Question 8

You run the command 'kubectl get pods -n default' and see no pods listed. However, you are sure there should be pods. What is the most likely cause?

Accepted Answer

The current kubectl context is connected to a different cluster. If kubectl shows no pods but you expect them, the most common cause is that the current kubeconfig context is pointing to the wrong cluster or namespace. Option A is possible but less likely because default namespace typically has pods. Option B is correct. Option C would cause errors, not empty list. Option D is not a typical issue.

Answer

All pods are in the 'kube-system' namespace

Answer

The kube-apiserver is down

Answer

The pods are in the 'Pending' state and not listed

Question 9

What is the primary difference between a container and a virtual machine (VM)?

Accepted Answer

Containers share the host OS kernel, whereas VMs include a full guest OS. Containers share the host OS kernel, while VMs include a full guest OS. This makes containers more lightweight and portable.

Answer

Containers are slower to start than VMs

Answer

Containers provide stronger isolation than VMs

Answer

VMs are more portable than containers

Question 10

What is the purpose of the Container Runtime Interface (CRI) in Kubernetes?

Accepted Answer

To allow kubelet to use different container runtimes without modifying its code. CRI is a plugin interface that allows kubelet to use a variety of container runtimes without needing to recompile kubelet. It standardizes how kubelet communicates with the runtime.

Answer

To replace Docker as the only supported runtime

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To define the format of container images

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To provide a standard API for managing containers across different orchestration platforms

Question 11

Which of the following is a container runtime that implements the Container Runtime Interface (CRI)?

Accepted Answer

containerd. containerd is a core container runtime that implements the CRI and is commonly used in Kubernetes.

Answer

rkt

Answer

Docker

Answer

Hyper-V

Question 12

You have a Deployment running 3 replicas. You need to update the container image without downtime. Which command updates the image while performing a rolling update?

Accepted Answer

kubectl set image deployment/my-deployment nginx=nginx:1.25. The 'kubectl set image' command updates the container image in the Deployment, triggering a rolling update by default.

Answer

kubectl replace deployment my-deployment --image=nginx:1.25

Answer

kubectl scale deployment my-deployment --image=nginx:1.25

Answer

kubectl update deployment my-deployment --image=nginx:1.25

Question 13

A developer creates a Deployment with replicas: 3 and strategy type: RollingUpdate with maxSurge: 1 and maxUnavailable: 1. During a rolling update, the Deployment controller creates a new ReplicaSet. After the new ReplicaSet has 2 pods ready, the node running one of the original ReplicaSet's pods fails. What is the MOST likely number of total pods running after the node failure, assuming no other actions?

Accepted Answer

2 pods running. Option B is correct. Initially 3 old pods. maxSurge=1 allows up to 4 total pods. maxUnavailable=1 allows at least 2 available pods. After new ReplicaSet has 2 ready, controller would have scaled down old ReplicaSet to 1 (making total 3: 2 new + 1 old). Node failure kills the old pod. New ReplicaSet remains at 2. Total running = 2 (both new). Option A would only happen if no old pods were killed. Option C would require both old pods still running. Option D would be too many.

Answer

4 pods running

Answer

3 pods running

Answer

1 pod running

Question 14

Which TWO are characteristics of the microservices architecture that are supported by container orchestration?

Accepted Answer

Independent deployment of each service. Options A and D are correct. Microservices decompose an application into loosely coupled services (A) that can be deployed independently (D). Option B is false — microservices should be loose coupling. Option C is false — microservices favor decentralized data management. Option E is false — microservices are typically small, not monolithic.

Answer

Tight coupling between services to ensure performance

Answer

Monolithic codebase with centralized deployment

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Use of a single, shared database for all services

Question 15

Which command would you use to view the logs of a specific container in a multi-container pod?

Accepted Answer

kubectl logs mypod -c mycontainer. The -c flag specifies the container name within the pod.

Answer

kubectl logs mycontainer -p mypod

Answer

kubectl logs mypod --container mycontainer

Answer

kubectl logs mypod mycontainer

Question 16

Which of the following is a characteristic of immutable infrastructure?

Accepted Answer

Infrastructure components are never changed after deployment; they are replaced. Immutable infrastructure means that instead of modifying existing servers, new instances are created from an image and old ones are replaced.

Answer

Infrastructure is version-controlled using Git

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Servers are updated in-place with configuration management tools

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Containers are used to ensure portability

Question 17

What is the Container Runtime Interface (CRI)?

Accepted Answer

An API between kubelet and container runtime. CRI is a plugin interface that enables kubelet to use different container runtimes without needing to recompile.

Answer

A tool for building container images

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A standard for container runtime logs

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A specification for container images

Question 18

Which command is used to create a Deployment that runs an nginx container with 3 replicas?

Accepted Answer

kubectl create deployment nginx --image=nginx --replicas=3. The correct command uses 'kubectl create deployment' with the --image and --replicas flags.

Answer

kubectl create pod nginx --image=nginx --replicas=3

Answer

kubectl run nginx --image=nginx --replicas=3

Answer

kubectl scale deployment nginx --replicas=3

Question 19

Which THREE are valid ways to perform a rolling update of a Deployment in Kubernetes? (Select THREE.)

Accepted Answer

Update the container image to a new version. A rolling update can be triggered by updating the container image, changing the image tag, or modifying a label selector (though changing selector is not recommended). Scaling is not an update.

Answer

Manually delete all pods and let the Deployment recreate them

Answer

Change the number of replicas

Question 20

You have a Deployment with three replicas. You want to update the container image but ensure that only one pod is updated at a time, and the update proceeds only if the new pod becomes healthy. Which update strategy should you configure?

Accepted Answer

RollingUpdate with maxSurge=1 and maxUnavailable=0. RollingUpdate with maxSurge=1 and maxUnavailable=0 ensures one pod is updated at a time and the update pauses if the new pod is not healthy.

Answer

RollingUpdate with maxSurge=3 and maxUnavailable=1

Answer

Canary deployment via Ingress

Answer

Recreate strategy