KCNA Kubernetes Fundamentals Practice Test 26 — 15 Questions

Question 1

You have a Deployment that uses a ConfigMap for configuration. You update the ConfigMap with new data. However, the pods in the Deployment continue to use the old configuration. What is the most likely reason?

Accepted Answer

The ConfigMap is mounted as a volume, and the pods have not been restarted. When a ConfigMap is mounted as a volume in a Pod, updates to the ConfigMap are automatically propagated to the mounted files, but the running process inside the container does not automatically reload the configuration. The Pod must be restarted (e.g., by rolling update or manual deletion) for the application to read the new values. This is the most common reason for stale configuration in a Deployment.

Answer

The ConfigMap data is immutable and cannot be updated

Answer

The ConfigMap is referenced by a different name in the pod spec

Answer

The Deployment's update strategy is set to Recreate

Question 2

Which TWO of the following are valid uses of Kubernetes Namespaces? (Select 2)

Accepted Answer

Enforcing network policies per namespace. Option B is correct because Kubernetes NetworkPolicies are namespace-scoped resources that allow you to define ingress and egress traffic rules for pods within a specific namespace. By applying a NetworkPolicy to a namespace, you can isolate workloads from each other, controlling which pods can communicate based on labels and ports, which is a fundamental use of namespaces for security and segmentation.

Answer

Setting CPU and memory limits at the namespace level

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Isolating node resources for different workloads

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Enabling RBAC authentication for users in a namespace

Question 3

Which TWO of the following are responsibilities of the kubelet? (Select 2)

Accepted Answer

Registering the node with the cluster and reporting node status. The kubelet is the node agent that ensures containers are running and healthy, and it reports node status to the control plane. kube-proxy handles network rules, and the scheduler assigns pods to nodes.

Answer

Scheduling pods onto nodes based on resource availability

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Creating and managing network iptables rules for Services

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Storing cluster configuration data

Question 4

Which THREE of the following are valid reasons to use a StatefulSet instead of a Deployment? (Select 3)

Accepted Answer

You need stable, unique network identifiers (e.g., pod hostnames) that persist across reschedules. StatefulSets provide stable, unique network identifiers (e.g., pod hostnames) that persist across reschedules because each pod gets a fixed ordinal index (e.g., pod-0, pod-1) and a corresponding DNS name (e.g., pod-0.statefulset.namespace.svc.cluster.local). This is essential for applications like databases (e.g., Cassandra, ZooKeeper) that rely on consistent peer discovery and identity, which Deployments cannot guarantee since they assign random pod names and IPs.

Answer

You only need a single instance of the application

Answer

You need to deploy a stateless web application with multiple replicas

Question 5

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

Answer

etcd

Question 6

What is the primary purpose of a Kubernetes Service?

Accepted Answer

To expose a set of pods as a network service with a stable endpoint. A Kubernetes Service provides a stable network endpoint (IP address and DNS name) to access a set of pods, which are ephemeral and can be rescheduled with different IPs. It acts as an abstraction layer, enabling load-balanced traffic to the pods via kube-proxy and iptables/IPVS rules. This is the core purpose of a Service, as defined in the Kubernetes API.

Answer

To provide persistent storage for pods

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To store configuration data for pods

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To manage rolling updates of applications

Question 7

Which kubectl command would you use to view the detailed state of a pod named 'web-pod' in the 'default' namespace?

Accepted Answer

kubectl describe pod web-pod. Option C is correct because `kubectl describe pod web-pod` retrieves a detailed, multi-section view of the pod's current state, including events, conditions, container statuses, and resource usage. This command is specifically designed for deep inspection of a Kubernetes resource, unlike `kubectl get` which shows a summary, or `kubectl logs` which shows container output.

Answer

kubectl logs web-pod

Answer

kubectl get pod web-pod

Answer

kubectl exec web-pod -- /bin/sh

Question 8

You have a Deployment named 'frontend' with 3 replicas. You want to perform a rolling update to a new container image. Which command should you use?

Accepted Answer

kubectl set image deployment/frontend container1=nginx:1.20. The `kubectl set image` command is the correct way to perform a rolling update on a Deployment. It directly updates the container image in the pod template, triggering a rolling update where the ReplicaSet gradually replaces old pods with new ones, ensuring zero downtime. Option A specifies the exact container name and new image, which matches the required syntax for a targeted update.

Answer

kubectl replace deployment frontend --image=nginx:1.20

Answer

kubectl edit deployment frontend --image=nginx:1.20

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kubectl update deployment frontend --image=v2

Question 9

A pod is stuck in 'Pending' state. Which of the following is the MOST likely cause?

Accepted Answer

There are no nodes with enough resources to run the pod. A pod stays pending when it cannot be scheduled to a node, typically due to insufficient resources or node selector issues.

Answer

The pod has been deleted

Answer

The container image is invalid

Answer

The pod's liveness probe is failing

Question 10

Which Kubernetes object is used to store non-confidential configuration data that can be consumed by pods?

Accepted Answer

ConfigMap. ConfigMap is the correct Kubernetes object for storing non-confidential configuration data, such as environment variables, command-line arguments, or configuration files, that can be consumed by pods. Unlike Secrets, ConfigMaps store data in plain text and are designed for configuration that does not require encryption, making them ideal for application settings that are not sensitive.

Answer

ServiceAccount

Answer

Secret

Answer

PersistentVolume

Question 11

You want to expose a set of pods running on node port 30080 to external traffic. Which Service type should you use?

Accepted Answer

NodePort. Option C (NodePort) is correct because a NodePort service exposes the application on a static port (30080) on each node's IP address, making it accessible from outside the cluster via <NodeIP>:30080. This is the appropriate choice when you need to expose pods to external traffic using a specific port number without requiring a cloud load balancer.

Answer

ExternalName

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LoadBalancer

Answer

ClusterIP

Question 12

What is the purpose of a liveness probe in a Kubernetes pod?

Accepted Answer

To check if the application is still running; if not, restart the container. A liveness probe in Kubernetes is used to determine if a container is still running and healthy. If the probe fails, the kubelet kills the container and restarts it based on the pod's restart policy. This ensures that applications that have entered a deadlock or hung state are automatically recovered without manual intervention.

Answer

To check if the pod is scheduled on a node

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To check if the container has started successfully

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To check if the application is ready to serve traffic

Question 13

You create a Deployment with replicas: 3. You then scale the Deployment to 5 replicas. What is the order of operations that the Deployment controller follows?

Accepted Answer

It updates the existing ReplicaSet's replica count to 5, and the ReplicaSet creates the new pods. When you scale a Deployment, the Deployment controller updates the replica count on the existing ReplicaSet that matches the pod template. The ReplicaSet controller then observes the desired count and creates the additional pods to reach the new target. This ensures that the Deployment's rollout history and rollback capabilities remain intact.

Answer

It creates a new ReplicaSet with 5 replicas and deletes the old one

Answer

It directly creates 2 new pods without using a ReplicaSet

Answer

It creates 2 new pods immediately without modifying the existing ReplicaSet

Question 14

A developer wants to inject environment variables into a pod from a ConfigMap named 'app-config'. Which YAML snippet correctly mounts all key-value pairs from the ConfigMap as environment variables?

Accepted Answer

envFrom:
  - configMapRef:
      name: app-config. Option B is correct because `envFrom` with a `configMapRef` injects all key-value pairs from the ConfigMap named 'app-config' as environment variables into the container. This is the standard Kubernetes method for bulk injection of ConfigMap data into environment variables, as opposed to selecting individual keys.

Answer

env:
  - name: CONFIG
    value: "$(CONFIGMAP)"

Answer

volumes:
  - name: config
    configMap:
      name: app-config
    volumeMounts:
      - name: config
        mountPath: /etc/config

Answer

env:
  - name: CONFIG
    valueFrom:
      configMapKeyRef:
        name: app-config
        key: config.yaml

Question 15

You have a Deployment with the following rollout strategy: rollingUpdate: maxSurge: 1, maxUnavailable: 0. What behavior does this configuration enforce?

Accepted Answer

The rollout will create one additional pod before terminating the old pod, ensuring zero downtime. Option D is correct because the rolling update strategy `maxSurge: 1, maxUnavailable: 0` ensures that during the rollout, one additional pod is created above the desired replica count before any existing pod is terminated. This guarantees that the total number of available pods never drops below the desired count, achieving zero downtime. The `maxUnavailable: 0` setting prevents any pod from being taken down until a new one is ready, while `maxSurge: 1` allows one extra pod to be created temporarily.

Answer

The rollout will terminate all old pods at once and then create new ones

Answer

The rollout will create all new pods first, then delete all old pods

Answer

The rollout will terminate one old pod before creating a new one