KCNA Practice Test 10 — 10 Questions

Question 1

You have a web application that needs to read configuration from a file and also access a database password. Which combination of resources should you use to manage these configurations securely?

Accepted Answer

Use ConfigMap for configuration file and Secret for database password. ConfigMap is designed for storing non-confidential configuration data like configuration files, while Secret is specifically for sensitive data such as database passwords. Secrets are base64-encoded and can be encrypted at rest using etcd encryption or KMS, providing a security boundary that ConfigMaps lack. This combination follows Kubernetes best practices for separating configuration from secrets.

Answer

Use ConfigMap for both

Answer

Use PersistentVolume for configuration and environment variables for the password

Answer

Use Secret for both

Question 2

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 3

A developer deploys a pod with the following resource specification:
```yaml
resources:
  requests:
    memory: "256Mi"
  limits:
    memory: "512Mi"
```
The pod is killed with OOMKilled. What is the most likely cause?

Accepted Answer

The container exceeded the memory limit of 512Mi. The OOMKilled exit code indicates the container was terminated by the Linux kernel's Out-Of-Memory (OOM) killer because it attempted to use more memory than its configured limit of 512Mi. Kubernetes enforces memory limits using cgroups; when the container exceeds the limit, the kernel kills the process, resulting in the OOMKilled status.

Answer

The container exceeded the memory request of 256Mi

Answer

The node ran out of memory

Answer

The CPU limit was too low

Question 4

A microservice application is experiencing high latency during traffic spikes. The team identifies that the database connection pool is exhausted. They want to implement a pattern that helps decouple the microservice from direct database connections and smooth out traffic bursts. Which design pattern should they apply?

Accepted Answer

Queue-based Load Leveling pattern. The Queue-based Load Leveling pattern uses a message queue (e.g., RabbitMQ, Amazon SQS) as a buffer between the microservice and the database. When traffic spikes occur, requests are queued and processed at a manageable rate, preventing the database connection pool from being exhausted. This decouples the service from direct database connections and smooths out bursts, directly addressing the latency issue.

Answer

Bulkhead pattern

Answer

Circuit Breaker pattern

Answer

Retry pattern

Question 5

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

Accepted Answer

The pod's resource requests exceed available node capacity and a node taint is not tolerated. The pod is in 'Pending' state because the scheduler cannot find a node that meets its requirements. The event '0/3 nodes are available: 1 node had taint that the pod didn't tolerate, 2 Insufficient cpu' directly indicates that the pod's resource requests exceed the available CPU on two nodes, and the remaining node has a taint that the pod does not tolerate. This matches option B: the pod's resource requests exceed available node capacity and a node taint is not tolerated.

Answer

The pod's liveness probe is failing

Answer

The pod's container runtime is not installed

Answer

The pod's image pull secret is missing

Question 6

Which Kubernetes resource is best suited for running a batch processing job that must complete successfully exactly once?

Accepted Answer

Job. A Kubernetes Job is designed specifically for batch processing tasks that need to run to completion exactly once. It creates one or more Pods and ensures that a specified number of them successfully terminate, making it ideal for workloads like data processing or backups that must finish without retries or restarts.

Answer

DaemonSet

Answer

Deployment

Answer

CronJob

Question 7

Which two statements correctly describe etcd in a Kubernetes cluster?

Accepted Answer

It is a key-value store that holds cluster configuration and state. etcd is a distributed, consistent key-value store used by Kubernetes to persist all cluster data, including configuration, state, and metadata. It is the single source of truth for the cluster, and the API server reads from and writes to it exclusively. Without etcd, the cluster cannot recover or maintain its desired state, making it a critical component.

Answer

It runs on every worker node

Answer

It manages network rules for Services

Answer

It implements the Kubernetes API

Question 8

A developer creates a Deployment with 3 replicas. The developer runs 'kubectl get pods' immediately after creation and sees that only 1 pod is in Running state, and the other 2 are Pending. What is the most likely reason for this?

Accepted Answer

The cluster does not have enough resources (CPU/memory) to schedule the additional pods. When a Pod remains in Pending state, it indicates that the scheduler cannot find a suitable node to place it. The most common cause is insufficient cluster resources (CPU or memory) to accommodate the additional Pods, as the scheduler checks node allocatable resources against Pod resource requests. With 2 out of 3 Pods pending, the cluster likely has enough resources for only one replica, leaving the others unscheduled.

Answer

The Deployment's YAML has a syntax error

Answer

The container image is not available on the worker nodes

Answer

The kubelet on the node is not running

Question 9

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

Accepted Answer

kube-controller-manager. The kube-controller-manager is the component that runs controller loops to regulate the state of the cluster. Each controller (e.g., Node Controller, Replication Controller) watches the shared state via the API server and makes changes to drive the actual cluster state toward the desired state defined in the control plane. This is the core mechanism for self-healing and maintaining declarative configuration.

Answer

etcd

Answer

kube-apiserver

Answer

kube-scheduler

Question 10

What is the OCI (Open Container Initiative) responsible for?

Accepted Answer

Defining standards for container images and runtimes. The Open Container Initiative (OCI) is a Linux Foundation project that defines open industry standards for container image formats and container runtimes. Its two main specifications are the OCI Image Spec (which standardizes the container image layout, including layers and manifests) and the OCI Runtime Spec (which defines the lifecycle and configuration for running containers). This ensures interoperability between different container tools and platforms, such as Docker, Podman, and containerd.

Answer

Hosting public container images

Answer

Providing a default container runtime for Kubernetes

Answer

Managing container orchestration