KCNA Kubernetes Fundamentals Practice Test 21 — 15 Questions

Question 1

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

Answer

Deployment

Answer

StatefulSet

Question 2

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

Answer

kubectl logs sidecar app

Answer

kubectl logs sidecar -p app

Question 3

A pod is stuck in Terminating state for several minutes. What is the most likely cause?

Accepted Answer

The node is unreachable or the kubelet is not responding. When a pod is stuck in Terminating state, the most likely cause is that the node where the pod was running is unreachable or the kubelet is not responding. The kubelet is responsible for executing the pod's termination lifecycle, including sending SIGTERM and, after the grace period, SIGKILL. If the kubelet cannot communicate with the API server (e.g., due to node failure, network partition, or kubelet crash), the pod's finalizer cannot be removed, leaving it stuck in Terminating.

Answer

The deployment is configured with a grace period

Answer

The pod has a liveness probe that is failing

Answer

The pod's container runtime is paused

Question 4

Which TWO of the following are valid methods for exposing a Service externally?

Accepted Answer

LoadBalancer. (LoadBalancer) is correct because it provisions an external load balancer (e.g., AWS ELB, GCP TCP LB) that assigns a public IP address to the Service, making it accessible from outside the cluster. Option E (NodePort) is correct because it exposes the Service on a static port (30000–32767) on every Node's IP, allowing external traffic to reach the Service via `:`. Both are valid Service types in Kubernetes for external exposure.

Answer

ExternalName

Answer

Ingress

Answer

ClusterIP

Question 5

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. The kube-controller-manager runs controller processes that regulate the state of the cluster. The replication controller (part of the controller manager) ensures that the actual number of pod replicas matches the desired count specified in a ReplicaSet or ReplicationController, automatically creating or terminating pods as needed. Additionally, the node controller within the kube-controller-manager periodically checks node health via the Node Lifecycle Controller, which monitors heartbeats (NodeStatus updates) and responds to node failures by tainting the node and evicting pods after a configurable timeout (default 5 minutes).

Answer

Storing cluster state

Answer

Exposing the Kubernetes API

Answer

Assigning pods to nodes

Question 6

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

Answer

etcd

Answer

kube-apiserver

Question 7

What is the smallest deployable unit in Kubernetes that can be created and managed?

Accepted Answer

Pod. The Pod is the smallest and simplest unit in the Kubernetes object model that you can create and manage. It represents a single instance of a running process in the cluster and encapsulates one or more containers, shared storage, and a unique cluster IP. While containers are the runtime units, Kubernetes does not manage containers directly; it manages Pods, which are the atomic scheduling unit.

Answer

Container

Answer

Service

Answer

Deployment

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

Answer

kubectl replace -f updated-deployment.yaml

Answer

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

Answer

The container runtime is not installed on any node

Answer

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

Question 10

You need to provide an application with configuration data that does not change often and should not be baked into the container image. Which Kubernetes resource should you use?

Accepted Answer

ConfigMap. ConfigMap is the correct Kubernetes resource for providing configuration data that does not change often and should not be baked into the container image. It decouples configuration artifacts from image content, allowing you to update configuration without rebuilding images, and supports injection via environment variables, command-line arguments, or volume mounts.

Answer

Secret

Answer

PersistentVolumeClaim

Answer

ServiceAccount

Question 11

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

Answer

ReplicationController

Answer

DaemonSet

Question 12

You have a Deployment with 3 replicas. You need to perform a rolling update with 2 extra pods during the update and ensure that only 1 pod is unavailable at any time. Which update strategy configuration achieves this?

Accepted Answer

maxSurge: 2, maxUnavailable: 1. It sets maxSurge to 2 (allowing up to 2 extra pods above the desired 3, for a total of 5 pods during the update) and maxUnavailable to 1 (ensuring at most 1 pod is unavailable at any time). This satisfies the requirement of having 2 extra pods during the update while keeping only 1 pod unavailable.

Answer

maxSurge: 1, maxUnavailable: 2

Answer

maxSurge: 0, maxUnavailable: 2

Answer

maxSurge: 3, maxUnavailable: 0

Question 13

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

Answer

kube-proxy

Answer

container runtime

Question 14

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.

Answer

Service of type NodePort

Answer

Ingress

Answer

NetworkPolicy

Question 15

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 indicates the application cannot connect to the database. Since other pods can reach the database, the issue is specific to this pod. A common cause is that the pod's configuration (e.g., environment variables, config file) contains wrong connection details, such as incorrect service name, port, or credentials.

Answer

The kube-proxy is not functioning

Answer

The pod's resource limits are too low

Answer

The database pod is not running