KCNA Kubernetes Fundamentals Practice Test 24 — 15 Questions

Question 1

What is the primary purpose of the `kubectl apply` command?

Accepted Answer

To create or update resources from a manifest. The `kubectl apply` command uses a declarative approach to manage Kubernetes resources. It sends a PATCH request to the API server, which compares the desired state in the provided manifest (YAML/JSON) with the current state of the resource in the cluster. If the resource does not exist, it creates it; if it does exist, it updates only the fields specified in the manifest, preserving any fields not mentioned.

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To view resource details

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To delete resources

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To execute commands inside a container

Question 2

You need to run a one-time batch job that processes data and then exits. The job should run to completion and not be restarted. Which Kubernetes resource should you use?

Accepted Answer

Job. A Kubernetes Job is designed for one-time batch processing tasks that run to completion and are not restarted. It creates one or more Pods and ensures they successfully terminate, making it the correct choice for a non-repeating, finite workload.

Answer

DaemonSet

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Deployment

Answer

StatefulSet

Question 3

A service of type ClusterIP is created but pods cannot reach it using the service name. The pods are in the same namespace. What is a likely cause?

Accepted Answer

CoreDNS is not running or misconfigured. When a ClusterIP service cannot be reached by its DNS name from pods in the same namespace, the most common cause is that CoreDNS (the cluster DNS resolver) is not running or is misconfigured. Kubernetes relies on CoreDNS to resolve service names to ClusterIP addresses; if CoreDNS is down or its configuration is incorrect, DNS queries for the service name will fail, even though the service itself and its endpoints are healthy.

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The service is not exposed externally

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The service port does not match the container port

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The selector does not match any pod labels

Question 4

Which command would you use to view the logs of a container named 'sidecar' inside a pod named 'app'?

Accepted Answer

kubectl logs app -c sidecar. The `kubectl logs` command uses the `-c` flag to specify a container name within a pod. When a pod contains multiple containers, you must explicitly indicate which container's logs to retrieve. The syntax `kubectl logs -c ` is the standard way to view logs from a specific container in a multi-container pod.

Answer

kubectl logs app sidecar

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kubectl logs sidecar app

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kubectl logs sidecar -p app

Question 5

Which THREE of the following are valid apiVersions for Kubernetes resources?

Accepted Answer

batch/v1. The three valid apiVersions here are batch/v1 (A), v1 (B), and apps/v1 (C). batch/v1 is the stable API group/version used for workload resources such as Job and CronJob, so it is a legitimate apiVersion value. v1 is the core (legacy) API group version used for resources like Pod, Service, ConfigMap, and Secret, and it is valid without a group prefix. apps/v1 is the stable API group/version for workloads such as Deployment, StatefulSet, DaemonSet, and ReplicaSet, making it valid as well. The unmarked options do not belong because extensions/v1beta1 (D) is a removed/deprecated API group version no longer served in modern Kubernetes clusters, and v1beta1 (E) is not a complete apiVersion by itself since a beta version must be qualified by its API group (for example, apps/v1beta1 or batch/v1beta1).

Answer

extensions/v1beta1

Answer

v1beta1

Question 6

Which TWO of the following are functions of the kube-controller-manager?

Accepted Answer

Managing replication and ensuring the desired number of pods are running. Option A is correct because the kube-controller-manager runs the ReplicationController/ReplicaSet controller, which continuously reconciles the actual number of running pods with the desired replica count specified in the resource. Option D is correct because the kube-controller-manager includes the node controller, which monitors node health via heartbeats/leases and responds to node failures by marking nodes NotReady and evicting or rescheduling their pods. Option B is incorrect because cluster state is persisted in etcd, not by the kube-controller-manager. Option C is incorrect because the Kubernetes API is exposed by the kube-apiserver. Option E is incorrect because pod-to-node assignment (scheduling) is performed by the kube-scheduler.

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Storing cluster state

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Exposing the Kubernetes API

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Assigning pods to nodes

Question 7

Which Kubernetes control plane 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 control plane 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 bring the current state closer to the desired state. It bundles together multiple controllers (e.g., Node Controller, Replication Controller, Endpoint Controller, Service Account Controller) that each handle a specific aspect of cluster management, ensuring the cluster's actual state matches the user-defined desired state.

Answer

kube-scheduler

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etcd

Answer

kube-apiserver

Question 8

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 9

A pod is stuck in Pending state. You run 'kubectl describe pod' and see the event '0/3 nodes are available: 1 node(s) had taint(s) that the pod didn't tolerate, 2 node(s) had insufficient memory.'. What is the most likely cause?

Accepted Answer

The pod does not have tolerations for the node's taints and memory is insufficient on other nodes. The event '0/3 nodes are available: 1 node(s) had taint(s) that the pod didn't tolerate, 2 node(s) had insufficient memory' directly indicates that the pod failed scheduling because it lacks required tolerations for a tainted node, and the remaining nodes do not have enough memory to satisfy the pod's resource requests. This matches option A, as the pod's tolerations are missing for the tainted node, and memory is insufficient on the other two nodes.

Answer

The kube-scheduler is not running

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The container runtime is not installed on any node

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The pod's resource requests exceed available resources on all nodes

Question 10

Which Kubernetes controller ensures that a specified number of pod replicas are running at all times?

Accepted Answer

ReplicaSet. A ReplicaSet is the Kubernetes controller that ensures a specified number of pod replicas are running at all times. It uses a label selector to match pods and maintains the desired replica count by creating or deleting pods as needed. ReplicaSet is the successor to ReplicationController and is primarily used by Deployments to manage pod scaling and self-healing.

Answer

Job

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ReplicationController

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DaemonSet

Question 11

Which component on a worker node is responsible for enforcing the desired state of pods as defined in the pod specification?

Accepted Answer

kubelet. The kubelet is the primary node agent that runs on each worker node and is responsible for ensuring that containers are running in a pod as specified by the pod's manifest (PodSpec). It continuously monitors pod status and takes corrective actions, such as restarting containers or re-creating pods, to match the desired state defined in the Kubernetes API.

Answer

kube-scheduler

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kube-proxy

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container runtime

Question 12

You need to expose a set of pods running a web application to internal cluster traffic on a stable IP address. Which resource should you create?

Accepted Answer

Service of type ClusterIP. A Service of type ClusterIP exposes the set of pods on a stable, internal IP address that is only reachable within the cluster. This is the default Service type and is specifically designed for internal cluster traffic, providing a stable virtual IP (VIP) that load-balances requests to the underlying pods.

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Service of type NodePort

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Ingress

Answer

NetworkPolicy

Question 13

A pod is in CrashLoopBackOff state. 'kubectl logs pod' shows 'Error: cannot connect to database at db-service:5432'. The database Service exists and is reachable from other pods. What is the most likely cause?

Accepted Answer

The application's configuration has incorrect database connection details. The error 'cannot connect to database at db-service:5432' while the Service is reachable from other pods strongly indicates the application's configuration (e.g., wrong hostname, port, credentials, or database name) is incorrect. Since other pods can reach the database, the issue is isolated to this pod's config, not cluster networking or the database itself. This is a classic misconfiguration scenario.

Answer

The kube-proxy is not functioning

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The pod's resource limits are too low

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The database pod is not running

Question 14

You want to run a batch job that processes data and then terminates. Which Kubernetes resource is best suited for this workload?

Accepted Answer

Job. A Kubernetes Job is designed for batch processing workloads that run to completion and then terminate. Unlike controllers that maintain a desired number of running Pods (like Deployments or StatefulSets), a Job creates one or more Pods and ensures they successfully exit. Once the specified number of successful completions is reached, the Job stops, making it the ideal choice for a one-time data processing task.

Answer

StatefulSet

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DaemonSet

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Deployment

Question 15

Which TWO of the following are valid Kubernetes resource types that can be used to store configuration data or secrets?

Accepted Answer

Secret. Option A (Secret) is correct because a Secret is a native Kubernetes API object specifically designed to hold sensitive configuration data such as passwords, tokens, and TLS keys, storing values as base64-encoded data or stringData. Option E (ConfigMap) is correct because a ConfigMap is the standard Kubernetes resource for storing non-confidential configuration data as key-value pairs that pods can consume via environment variables, command-line arguments, or mounted files. Option B (Volume) is not a configuration store; it is an abstraction for storage that a pod mounts, and while a ConfigMap or Secret can be projected into a Volume, the Volume itself holds filesystem data, not configuration objects. Option C (PersistentVolumeClaim) is a request for persistent storage bound to a PersistentVolume, used for durable data rather than configuration or secret storage. Option D (ServiceAccount) provides an identity for processes running in a pod and is used for RBAC authentication/authorization, not for storing arbitrary configuration data or secrets.

Answer

Volume

Answer

PersistentVolumeClaim

Answer

ServiceAccount