KCNA Practice Test 3 — 30 Questions

Question 1

You want to run a batch job that processes a queue and then terminates. Which Kubernetes resource should you use?

Accepted Answer

Job. A Kubernetes Job is designed for batch processing tasks that run to completion and then terminate. It creates one or more Pods and ensures they successfully finish executing a specific workload, making it the correct choice for processing a queue and then exiting.

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Deployment

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CronJob

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DaemonSet

Question 2

What is the purpose of a Service in Kubernetes?

Accepted Answer

To expose a set of pods as a network service with a stable endpoint. A Service in Kubernetes provides a stable network endpoint (IP address and DNS name) to access a set of Pods, which are ephemeral and can be created or destroyed dynamically. It decouples the client from the Pods' IPs by using label selectors to route traffic, enabling reliable communication within the cluster or externally. This is defined in the Kubernetes API as a Service resource, with types like ClusterIP, NodePort, and LoadBalancer.

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To provide persistent storage volumes

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To manage rolling updates of pods

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To store configuration data as key-value pairs

Question 3

What is the primary benefit of using containers over virtual machines?

Accepted Answer

Containers are lightweight and share the host OS kernel. Containers are lightweight because they share the host OS kernel, avoiding the overhead of a separate guest OS per instance. Unlike VMs, which require a hypervisor and a full OS for each virtual machine, containers run as isolated processes on the same kernel, enabling faster startup times and higher density. This shared-kernel model is the primary benefit, as it reduces resource consumption and improves efficiency in orchestrated environments like Kubernetes.

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Containers provide stronger isolation between applications

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Containers include a full operating system per instance

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Containers require a hypervisor to run

Question 4

You want to update a Deployment's container image to v2 and perform a rolling update using the simplest imperative command. Which kubectl command achieves this?

Accepted Answer

kubectl set image deployment/my-deployment my-container=myapp:v2 --record. The `kubectl set image` command is the standard imperative way to update a container image in a Deployment, and it automatically triggers a rolling update. Option A is invalid; `kubectl update` is not a real command. Option B, `kubectl replace`, requires a full YAML file and is a declarative replacement operation, not a simple image update command. Option C, `kubectl patch`, can be used but is overly complex and error-prone for a simple image update. The question asks for the simplest imperative command, making D the best answer.

Answer

kubectl update deployment my-deployment --image=myapp:v2

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kubectl replace -f updated-deployment.yaml

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kubectl patch deployment my-deployment -p '{"spec":{"template":{"spec":{"containers":[{"name":"my-container","image":"myapp:v2"}]}}}}'

Question 5

Which component in an event-driven architecture is responsible for decoupling event producers from consumers?

Accepted Answer

Event broker. The event broker (e.g., Kafka, RabbitMQ, NATS) is the central component that receives events from producers and routes them to consumers, allowing producers and consumers to operate independently without direct knowledge of each other. It provides asynchronous, decoupled communication by buffering events, managing subscriptions, and ensuring delivery. This decoupling enables scalability, fault tolerance, and independent evolution of services.

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Config server

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API gateway

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Service mesh

Question 6

Which control plane component is responsible for assigning pods to nodes?

Accepted Answer

kube-scheduler. The kube-scheduler is the control plane component responsible for assigning pods to nodes. It watches for newly created pods that have no node assignment and selects an optimal node for each pod based on resource requirements, constraints, policies, and data locality. The scheduler does not actually run the pod; it updates the pod's `nodeName` field via the API server, which then triggers the kubelet on the chosen node to launch the pod.

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etcd

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kube-apiserver

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kube-controller-manager

Question 7

What is the main advantage of using OpenTelemetry over vendor-specific instrumentation libraries?

Accepted Answer

It provides a single, vendor-agnostic instrumentation standard. OpenTelemetry provides a unified standard that avoids vendor lock-in, allowing data to be sent to any backend.

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It eliminates the need for logging

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It automatically reduces latency

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It is the only tool that supports traces

Question 8

A developer wants to ensure that a pod runs only on nodes with SSDs. Which mechanism should be used?

Accepted Answer

Add a nodeSelector with disktype: ssd. `nodeSelector` is a simple and direct mechanism in Kubernetes to constrain a pod to run only on nodes that have a specific label, such as `disktype=ssd`. By labeling nodes with SSDs and adding the corresponding `nodeSelector` in the pod spec, the scheduler ensures the pod is placed exclusively on those nodes. This approach is straightforward and does not require complex scheduling constraints or resource management.

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Apply a taint to nodes without SSDs and add tolerations to the pod

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Use pod anti-affinity

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Define a ResourceQuota

Question 9

You need to run a batch job that processes a queue and then terminates. Which Kubernetes resource should you use?

Accepted Answer

Job. A Job is the correct Kubernetes resource for running a batch process that executes a finite task (e.g., processing a queue) and then terminates. Unlike controllers that maintain a desired state indefinitely, a Job creates one or more Pods and ensures they run to successful completion, after which the Job itself completes and no further Pods are created.

Answer

Deployment

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DaemonSet

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StatefulSet

Question 10

A team wants to deploy a stateful application that requires each pod to have a unique, stable network identity and persistent storage that persists across rescheduling. Which Kubernetes resource is most appropriate?

Accepted Answer

StatefulSet. StatefulSet is the correct choice because it provides each pod with a unique, stable network identity (via a predictable hostname derived from the StatefulSet name and ordinal index) and dedicated persistent storage that persists across rescheduling. This is achieved through a headless Service and PersistentVolumeClaims (PVCs) that are bound to each pod's identity, ensuring that when a pod is rescheduled, it reattaches to the same storage and retains its network identity.

Answer

DaemonSet

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Deployment

Answer

Job

Question 11

Which THREE are core principles of the Twelve-Factor App methodology?

Accepted Answer

Explicitly declare and isolate dependencies. Option B is correct because Factor II (Dependencies) requires an app to explicitly declare all dependencies via a manifest such as requirements.txt, package.json, or Gemfile, and isolate them using tooling like virtualenv or Bundler so no implicit system-wide packages are assumed. Option D is correct because Factor XI (Logs) states an app should never manage log files itself; instead it writes unbuffered event streams to stdout/stderr, letting the execution environment aggregate and route them. Option E is correct because Factor I (Codebase) mandates exactly one codebase tracked in a version control system such as Git, with many deploys from that same codebase across environments. Option A is wrong because Factor III (Config) requires config to be stored in the environment, not in the codebase, precisely to keep credentials and environment-specific values out of revision control. Option C is wrong because the methodology calls for loosely coupled, interchangeable backing services (Factor IV), attached and detached via config, not tight coupling.

Answer

Store config in codebase for traceability

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Tight coupling to backing services

Question 12

Which TWO of the following are characteristics of microservices architecture? (Choose 2)

Accepted Answer

Services can be deployed independently. Microservices architecture is defined by the ability to deploy each service independently without affecting other services. This independence enables teams to update, scale, and roll back individual components, which is a core principle of container orchestration platforms like Kubernetes that manage these services as separate units.

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All services share the same database

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The entire application is deployed as a single unit

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Services are tightly coupled

Question 13

Which kubectl command would you use to view the logs of a specific container named 'app' in a multi-container Pod named 'web-pod'?

Accepted Answer

kubectl logs web-pod -c app. The `kubectl logs` command uses the `-c` flag to specify a container name within a multi-container Pod. The correct syntax is `kubectl logs -c `, which targets the 'app' container inside 'web-pod'.

Answer

kubectl log web-pod container app

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kubectl logs web-pod app

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kubectl logs app web-pod

Question 14

A pod has resource requests of 512Mi memory and 500m CPU, and limits of 1Gi memory and 1 CPU. The node has 4Gi memory and 2 CPU cores. If the pod tries to use 700m CPU, what will happen?

Accepted Answer

The pod will be allowed to use 700m CPU. The pod's CPU request is 500m, and its CPU limit is 1 CPU (1000m). When the pod attempts to use 700m CPU, it is below the limit of 1000m, so it is allowed to burst up to that amount. Kubernetes uses the CPU request for scheduling and the limit for throttling; since 700m is within the limit, no throttling occurs. The pod is not evicted or terminated because it has not exceeded its memory limit or violated any resource constraints.

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The pod will be throttled to 500m CPU

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The pod will be evicted from the node

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The pod will be terminated for exceeding the limit

Question 15

In a container image built from a Dockerfile, what is the purpose of the CMD instruction?

Accepted Answer

To provide default arguments for the ENTRYPOINT instruction. The CMD instruction in a Dockerfile provides default arguments for the ENTRYPOINT instruction when the container is run. If no ENTRYPOINT is defined, CMD itself serves as the default command to execute. This allows users to override the default behavior at runtime by appending arguments to `docker run`, which replace the CMD values while preserving the ENTRYPOINT.

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To specify a command that always runs at build time

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To copy files into the image

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To define environment variables

Question 16

In the context of distributed tracing, what is a 'span'?

Accepted Answer

A single logical operation within a service, with a start and end time. A span represents a single logical operation within a service, with a start time and end time, forming the basic unit of work in distributed tracing. Spans are nested to form a trace, where the root span represents the overall request and child spans represent downstream calls, database queries, or internal operations.

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A metric that measures request latency

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A tool for collecting logs from containers

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The entire end-to-end transaction across services

Question 17

A developer wants to run a one-time task that creates a database schema and then exits. Which Kubernetes workload type is most appropriate?

Accepted Answer

Job. A Job is the correct choice because it is designed for finite, one-time tasks that run to completion, such as creating a database schema. Unlike long-running workloads, a Job creates one or more Pods and ensures they terminate successfully after the task finishes, making it ideal for batch processing or initialization tasks.

Answer

DaemonSet

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StatefulSet

Answer

Deployment

Question 18

Which Kubernetes component is responsible for maintaining the desired state of the cluster by running controllers?

Accepted Answer

kube-controller-manager. The kube-controller-manager is the component that runs controller processes, which are control loops that watch the shared state of the cluster through the kube-apiserver and make changes to drive the current state toward the desired state. It bundles together controllers such as the Node Controller, Replication Controller, and Endpoint Controller, each responsible for specific aspects of cluster state management.

Answer

kube-apiserver

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kube-scheduler

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etcd

Question 19

A team is designing a Kubernetes cluster for a production workload that requires high availability. They have three worker nodes in different availability zones. Which statement about scheduling Pods is correct?

Accepted Answer

Define a Pod topology spread constraint with topologyKey: topology.kubernetes.io/zone.. A Pod topology spread constraint with `topologyKey: topology.kubernetes.io/zone` explicitly instructs the scheduler to distribute Pods evenly across the specified failure domains (availability zones). This ensures that if one zone fails, the remaining zones still have running Pods, achieving high availability for the production workload.

Answer

Use nodeSelector to assign Pods to nodes in different zones.

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Add tolerations for the zone taint.

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Use podAntiAffinity with a requiredDuringSchedulingIgnoredDuringExecution rule.

Question 20

Which two of the following are valid ways to set resource constraints on a container in a Pod spec?

Accepted Answer

Specify 'resources.limits.memory' for maximum memory. Option B is correct because the Pod spec's container definition uses the 'resources.limits' field to declare the maximum amount of a resource the container may consume, so 'resources.limits.memory' sets a hard memory ceiling that the container cannot exceed. Option D is correct because 'resources.requests.cpu' declares the minimum CPU the container is guaranteed for scheduling purposes, and the kubelet uses this value when allocating CPU shares. The other options are invalid field names: 'resources.guarantees.cpu' (A), 'resources.min.memory' (C), and 'resources.max.cpu' (E) do not exist in the Kubernetes API, which only supports 'requests' and 'limits' under 'resources'.

Answer

Specify 'resources.guarantees.cpu' for CPU guarantees

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Specify 'resources.min.memory' for minimum memory

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Specify 'resources.max.cpu' for CPU limits