KCNA Container Orchestration Practice Test 13 — 15 Questions

Question 1

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 2

You are designing a microservices application. Which of the following is a key principle of microservices architecture?

Accepted Answer

Services are loosely coupled and can be deployed independently. Microservices architecture is fundamentally defined by loose coupling and independent deployability. Each service encapsulates its own domain logic, communicates via lightweight protocols like HTTP/REST or gRPC, and can be updated, scaled, or deployed without affecting other services. This aligns with the Kubernetes-native pattern of managing each microservice as a separate Deployment or StatefulSet, enabling continuous delivery and resilience.

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Services are tightly coupled to allow fast communication

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All services must be written in the same programming language

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All services must share a common database

Question 3

Which of the following is an example of immutable infrastructure?

Accepted Answer

Rebuilding a server from a pre-baked image and replacing the old one. Immutable infrastructure means that once a server or container is deployed, it is never modified in place. Instead, any change requires building a new image and redeploying. Option D describes exactly this: rebuilding from a pre-baked image and replacing the old server, which is the core pattern of immutability in container orchestration (e.g., Kubernetes rolling updates or Recreate deployments).

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SSH into a server to apply patches

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Manually installing packages on a running container

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Using configuration management tools to update software on running servers

Question 4

Which three of the following are benefits of container orchestration? (Choose three.)

Accepted Answer

High availability through replication. Container orchestration provides high availability via replicas, scaling (both manual and autoscaling), and self-healing (restarting failed containers). Bare metal performance is not a direct benefit of orchestration; it is a characteristic of containers themselves. Manual deployment is the opposite of orchestration.

Answer

Manual deployment of containers to specific hosts

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Bare metal performance

Question 5

Which two of the following are characteristics of container images built using OCI standards? (Choose two.)

Accepted Answer

They are portable across different container runtimes. OCI images are composed of layers (read-only) and are built from a Dockerfile. They are lightweight and portable across different runtimes. They do not include a guest OS (unlike VMs), and they are not tied to a specific runtime.

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They include a full guest operating system

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They can only be run by Docker

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They require a hypervisor to run

Question 6

Which of the following is a key benefit of container orchestration?

Accepted Answer

Automated scaling, self-healing, and declarative management. Container orchestration platforms like Kubernetes provide automated scaling, self-healing, and declarative management.

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Manual scaling of applications

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Requires manual intervention for pod failures

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Only supports monolithic applications

Question 7

What is the Container Runtime Interface (CRI)?

Accepted Answer

A plugin interface that allows kubelet to use a variety of container runtimes. The Container Runtime Interface (CRI) is a plugin interface that enables the kubelet to communicate with different container runtimes (e.g., containerd, CRI-O) without needing to know their internal implementation details. It defines a gRPC-based protocol for managing container lifecycles, image operations, and pod sandboxes, allowing Kubernetes to remain runtime-agnostic.

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A specification for container images

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A registry for storing container images

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A command-line tool for managing containers

Question 8

Which of the following is a key difference between containers and virtual machines?

Accepted Answer

Containers share the host OS kernel; VMs run a separate guest OS. The key difference is that containers virtualize at the operating system level, sharing the host OS kernel via namespaces and cgroups, while each virtual machine runs a full, separate guest OS on top of a hypervisor. This architectural distinction means containers are more lightweight and start faster, but VMs provide stronger isolation because they do not share the host kernel.

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Both containers and VMs share the host kernel

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Containers have a full guest OS, VMs share the host kernel

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Containers require a hypervisor, VMs do not

Question 9

A Kubernetes Deployment manages a set of pods. What is the primary purpose of a Deployment?

Accepted Answer

To declare the desired state for a set of pods and manage rolling updates. A Deployment provides declarative updates for Pods and ReplicaSets, enabling rolling updates and rollbacks.

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To store configuration data as key-value pairs

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To run a batch job to completion

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To expose a set of pods as a network service

Question 10

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

Accepted Answer

Insufficient cluster resources (CPU/memory) to schedule the pod. A pod stuck in 'Pending' state indicates that the pod has not been scheduled to a node. The most common cause is insufficient cluster resources (CPU/memory), as the Kubernetes scheduler cannot find a node that meets the pod's resource requests. This is a scheduling failure, not a runtime issue.

Answer

The pod's liveness probe failed

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The pod's readiness probe failed

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The container image is missing

Question 11

Which command would you run to get a list of all pods in all namespaces?

Accepted Answer

kubectl get pods --all-namespaces. `kubectl get pods --all-namespaces` (or its shorthand `-A`) retrieves pods from every namespace in the cluster. This flag overrides the default behavior of `kubectl get pods`, which only returns pods in the current namespace (usually `default`).

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kubectl get pods --namespace=*

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kubectl get pods --global

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kubectl get pods --include-uninitialized

Question 12

What is the purpose of a Readiness Probe in a Kubernetes pod?

Accepted Answer

To check if the container is ready to start accepting traffic. A Readiness Probe indicates whether a pod is ready to serve traffic; if it fails, the pod is removed from Service endpoints.

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To ensure the pod is scheduled on a specific node

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To restart the container if it becomes unresponsive

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To check if the container is running

Question 13

Which Kubernetes resource should be used to run a one-time task that performs a computation and then exits?

Accepted Answer

Job. A Kubernetes Job is designed specifically for finite, one-time tasks that run to completion and then exit. Unlike controllers that maintain a desired number of continuously running Pods, a Job creates one or more Pods and tracks their successful termination, making it the correct choice for a computation that should run once and stop.

Answer

DaemonSet

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StatefulSet

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Deployment

Question 14

What is the Open Container Initiative (OCI) 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 formats and runtimes. Specifically, it maintains the OCI Image Specification (which standardizes the container image format, including layers and configuration) and the OCI Runtime Specification (which defines the lifecycle and interface for container runtimes like runc). This ensures interoperability between different container tools and platforms.

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Certifying Kubernetes administrators

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Providing a hosted container registry

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Managing the Kubernetes source code

Question 15

A microservices application has multiple services that need to discover each other by name. Which Kubernetes object provides built-in service discovery via DNS?

Accepted Answer

Service. A Kubernetes Service object provides built-in service discovery via DNS. When a Service is created, the cluster's DNS (typically CoreDNS) automatically assigns it a DNS name in the format `..svc.cluster.local`, allowing other microservices to resolve the Service by name without hardcoding IP addresses or using external service registries.

Answer

Ingress

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Namespace

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ConfigMap