KCNA Container Orchestration Practice Test 8 — 15 Questions

Question 1

What is the primary difference between a container and a virtual machine (VM)?

Accepted Answer

Containers share the host OS kernel, whereas VMs include a full guest OS. The primary difference is that containers share the host operating system kernel and run as isolated user-space processes, while virtual machines include a full guest OS with its own kernel. This architectural distinction means containers are lightweight and start in seconds, whereas VMs require booting a complete OS. Option D correctly captures this fundamental difference.

Answer

Containers are slower to start than VMs

Answer

Containers provide stronger isolation than VMs

Answer

VMs are more portable than containers

Question 2

A DevOps engineer wants to deploy a stateful application that requires stable network identities and persistent storage. Which Kubernetes resource is most appropriate?

Accepted Answer

StatefulSet. StatefulSet is the correct choice because it is designed specifically for stateful applications that require stable, unique network identities (via headless Services and ordinal hostnames) and persistent storage (via PersistentVolumeClaims that persist across Pod rescheduling). Unlike Deployments, StatefulSet guarantees ordered, graceful deployment and scaling, which is essential for applications like databases or distributed systems that rely on stable identities.

Answer

DaemonSet

Answer

Deployment

Answer

ReplicaSet

Question 3

A pod is stuck in the Pending state. Running 'kubectl describe pod <pod-name>' shows the event: '0/3 nodes are available: 1 node had taint {node.kubernetes.io/disk-pressure: }, 2 nodes had taint {node.kubernetes.io/memory-pressure: }'. What is the most likely cause?

Accepted Answer

All nodes have taints that the pod does not have tolerations for. The pod is stuck in Pending because the scheduler cannot find a node that satisfies its scheduling constraints. The events show that all three nodes have taints (disk-pressure and memory-pressure), and the pod does not have corresponding tolerations to allow it to be scheduled on those nodes. Without tolerations, the pod is not permitted to run on any of the available nodes, leaving it in the Pending state.

Answer

The container image is not found in the registry

Answer

The pod has a resource request that exceeds available capacity on all nodes

Answer

The pod's liveness probe is failing

Question 4

An application requires that a specific set of pods be placed on nodes labeled with 'gpu=true'. Which Kubernetes field should be used in the pod spec to enforce this?

Accepted Answer

nodeSelector. `nodeSelector` is the simplest and most direct Kubernetes field for constraining a pod to nodes that have a specific label. By setting `nodeSelector: { gpu: 'true' }` in the pod spec, the scheduler will only place the pod on nodes that have the label `gpu=true`. This is a hard constraint that does not support complex expressions but is ideal for the stated requirement.

Answer

topologySpreadConstraints

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affinity.nodeAffinity

Answer

tolerations

Question 5

Which of the following is a benefit of using container orchestration platforms like Kubernetes?

Accepted Answer

Self-healing (automatic restart of failed containers). Kubernetes includes a built-in controller (the kubelet and ReplicaSet controller) that continuously monitors the desired state of pods. If a container fails or its process crashes, the kubelet automatically restarts it based on the pod's restart policy (e.g., Always), ensuring high availability without manual intervention. This self-healing capability is a core benefit of container orchestration, reducing downtime and operational overhead.

Answer

Increased network latency

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Manual scaling of applications

Answer

Tighter coupling between microservices

Question 6

A user runs 'kubectl exec -it pod1 -- /bin/sh' and gets the error: 'error: unable to upgrade connection: container not found ("app")'. The pod has one container named 'app'. What is the most likely cause?

Accepted Answer

The pod is in a CrashLoopBackOff state. The error 'unable to upgrade connection: container not found ("app")' indicates that kubectl cannot find a running container named 'app' to attach to. When a pod is in CrashLoopBackOff state, the container repeatedly crashes and restarts, but during the backoff period the container is not running, so kubectl exec cannot locate it. This is the most likely cause because the error specifically mentions the container name, and a CrashLoopBackOff means the container is not in a running state.

Answer

The pod is running on a different node

Answer

The container image does not have /bin/sh

Answer

The container name is misspelled

Question 7

Which command is used to create a Deployment that runs an nginx container with 3 replicas?

Accepted Answer

kubectl create deployment nginx --image=nginx --replicas=3. `kubectl create deployment` is the standard Kubernetes command to create a Deployment resource, and the `--replicas=3` flag directly sets the desired replica count to 3. This command creates a Deployment that manages a ReplicaSet to ensure three nginx pods are running and maintained.

Answer

kubectl create pod nginx --image=nginx --replicas=3

Answer

kubectl run nginx --image=nginx --replicas=3

Answer

kubectl scale deployment nginx --replicas=3

Question 8

A company wants to run a batch job that processes data and then terminates. Which Kubernetes resource should they use?

Accepted Answer

Job. A Job is the correct Kubernetes resource for a batch job that processes data and then terminates. Unlike controllers that maintain a desired state (like Deployments), a Job creates one or more Pods and ensures they run to successful completion. Once the specified number of Pods terminate successfully, the Job is considered complete and does not restart the Pods, making it ideal for one-off or finite processing tasks.

Answer

CronJob

Answer

Deployment

Answer

DaemonSet

Question 9

When using a Service of type ClusterIP, how do pods reach the service?

Accepted Answer

Via the service's cluster IP and port. A Service of type ClusterIP exposes a stable virtual IP (the cluster IP) and port within the cluster. Pods reach the Service by sending traffic to this cluster IP and port, which is then load-balanced by kube-proxy (using iptables, IPVS, or eBPF rules) to one of the backing pod endpoints. This is the default and most fundamental Service type in Kubernetes.

Answer

Via the node's IP address and a high port

Answer

Via an external load balancer

Answer

Directly via the pod's IP address

Question 10

An administrator needs to expose a set of pods running a web application on a static port on each node's IP address. Which Service type should they use?

Accepted Answer

NodePort. A NodePort service exposes the application on a static port (30000–32767) on every node's IP address, making the pods accessible externally via :. This matches the requirement to expose pods on a static port on each node's IP address without needing an external load balancer.

Answer

ClusterIP

Answer

ExternalName

Answer

LoadBalancer

Question 11

Which TWO statements about containers are true compared to virtual machines? (Select TWO.)

Accepted Answer

Containers are more lightweight and start faster than VMs. Containers share the host OS kernel and run as isolated processes, requiring no hypervisor or full OS boot. This makes them lightweight (megabytes vs gigabytes) and allows them to start in milliseconds, whereas VMs must boot a full guest OS, which takes seconds to minutes.

Answer

Containers include a full guest operating system

Answer

Containers provide stronger isolation than VMs

Answer

Containers require a hypervisor to run

Question 12

Which THREE are valid ways to perform a rolling update of a Deployment in Kubernetes? (Select THREE.)

Accepted Answer

Update the container image to a new version. Changing the container image in a Deployment's pod template triggers a rolling update. Kubernetes compares the current pod template hash with the desired one; when they differ, it creates new ReplicaSets with the updated image and gradually scales down the old ReplicaSet while scaling up the new one, ensuring zero-downtime updates.

Answer

Manually delete all pods and let the Deployment recreate them

Answer

Change the number of replicas

Question 13

Which TWO are benefits of using a container orchestration platform like Kubernetes? (Select TWO.)

Accepted Answer

Automatic service discovery and load balancing. Kubernetes includes built-in service discovery and load balancing. Services in Kubernetes get a stable virtual IP and DNS name, and kube-proxy implements load balancing across pods using iptables or IPVS rules, distributing traffic without manual configuration.

Answer

Increases application complexity

Answer

Requires a dedicated hypervisor for each container

Answer

Manual scaling of applications

Question 14

A pod in the 'production' namespace is in a CrashLoopBackOff state. The pod has been running successfully for several days. You run 'kubectl describe pod app-pod -n production' and see the message: 'OOMKilled'. What is the MOST appropriate action to resolve this issue?

Accepted Answer

Increase the memory limit in the pod's container resource specification. The OOMKilled status indicates the container was terminated because it exceeded its memory limit. Increasing the memory limit in the pod's container resource specification directly addresses the root cause by allowing the container to use more memory before being killed. This is the most appropriate action because the pod was running successfully for days, suggesting a gradual memory growth or a recent workload change rather than a configuration error.

Answer

Increase the CPU request for the container

Answer

Delete and recreate the pod to clear the crash loop

Answer

Delete the namespace and redeploy all workloads

Question 15

What is the primary benefit of using containers over virtual machines?

Accepted Answer

Containers are lightweight and share the host OS kernel. Containers are lightweight because they share the host OS kernel, avoiding the overhead of a separate guest OS per instance. Unlike VMs, which require a hypervisor and a full OS for each virtual machine, containers run as isolated processes on the same kernel, enabling faster startup times and higher density. This shared-kernel model is the primary benefit, as it reduces resource consumption and improves efficiency in orchestrated environments like Kubernetes.

Answer

Containers provide stronger isolation between applications

Answer

Containers include a full operating system per instance

Answer

Containers require a hypervisor to run