KCNA Practice Test 10 — 10 Questions

Question 1

You have a Deployment that runs a web application. You need to expose this application externally on a fixed port using a cloud load balancer. Which Service type should you use?

Accepted Answer

LoadBalancer. A LoadBalancer Service type provisions an external cloud load balancer (e.g., AWS ELB, GCP TCP/UDP Load Balancer) that exposes the application on a fixed port (typically 80/443) and distributes traffic to the Pods. This is the correct choice because the requirement explicitly asks for a cloud load balancer with a fixed external port, which is exactly what LoadBalancer provides by integrating with the underlying cloud provider's API.

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NodePort

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ExternalName

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ClusterIP

Question 2

What is the purpose of a circuit breaker pattern in microservices?

Accepted Answer

To stop cascading failures by preventing calls to a failing service. The circuit breaker pattern wraps calls to a remote service and monitors for failures. When failures exceed a threshold, the breaker 'opens' and subsequent calls fail fast (or return a fallback) instead of being attempted, preventing a single failing dependency from exhausting threads/connections and cascading failures across the microservice graph. This is the core purpose: fault isolation and preventing cascading failures.

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To distribute traffic across multiple instances

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To encrypt communication between services

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To automatically retry failed requests

Question 3

You need to ensure that a pod runs on a specific node that has an SSD. The node has the label 'disktype=ssd'. How should you configure the pod to target this node?

Accepted Answer

Set spec.nodeSelector with disktype: ssd.. `spec.nodeSelector` is the simplest and most direct way to constrain a Pod to run only on nodes that have a specific label. By setting `disktype: ssd` in the nodeSelector, the scheduler will only consider nodes with that exact label key-value pair, ensuring the Pod lands on an SSD-equipped node.

Answer

Set spec.affinity.nodeAffinity with requiredDuringSchedulingIgnoredDuringExecution.

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Set spec.tolerations with key=disktype, value=ssd.

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Set spec.nodeName to the node's name.

Question 4

A Pod is stuck in 'Pending' state. Which command is most helpful to diagnose the issue?

Accepted Answer

kubectl describe pod my-pod. 'kubectl describe pod my-pod' provides detailed information about the pod's current state, including events, conditions, and resource constraints. When a pod is stuck in 'Pending', it typically means the scheduler cannot place it on a node due to issues like insufficient CPU/memory, persistent volume claims not being bound, or node selector mismatches. The 'describe' command surfaces these specific reasons in the 'Events' section and 'Conditions' field, making it the most direct diagnostic tool.

Answer

kubectl logs my-pod

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kubectl get events

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kubectl top pod my-pod

Question 5

Which TWO of the following are true about the Open Container Initiative (OCI)?

Accepted Answer

OCI is a Linux Foundation project. The Open Container Initiative (OCI) is a Linux Foundation project that was established to create open industry standards around container formats and runtimes. It operates under the Linux Foundation's governance to ensure vendor-neutral specifications.

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OCI requires the use of containerd

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OCI defines the Dockerfile format

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OCI defines the Container Runtime Interface (CRI)

Question 6

A Pod has been in 'Pending' state for an unusual amount of time. Which of the following is a likely cause?

Accepted Answer

The cluster does not have enough resources to schedule the Pod. A Pod stuck in 'Pending' state indicates that the Pod has been accepted by the API server but has not been scheduled to a node. The most common cause is insufficient cluster resources (CPU, memory, or ephemeral storage) across all nodes, preventing the scheduler from finding a suitable node that meets the Pod's resource requests. The scheduler continuously evaluates nodes using predicates and priorities, and if no node passes the predicates (e.g., NodeResourcesFit), the Pod remains Pending.

Answer

The container image is invalid

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The Pod's liveness probe is failing

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The Service pointing to the Pod is misconfigured

Question 7

In the context of the 12-factor app methodology, which factor emphasizes storing configuration in environment variables?

Accepted Answer

Config. The Config factor in the 12-factor app methodology states that configuration should be stored in environment variables, not in code or config files. This allows the same codebase to be deployed across environments by injecting different configurations at runtime.

Answer

Backing services

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Dependencies

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Codebase

Question 8

Which of the following is a way to provide configuration data to a pod without baking it into the container image?

Accepted Answer

Using a ConfigMap. A ConfigMap is a Kubernetes API object used to decouple configuration artifacts from container images, allowing you to inject configuration data (e.g., environment variables, command-line arguments, or configuration files) into pods without rebuilding the image. This is the standard way to provide non-sensitive configuration data to pods at runtime, as defined in the Kubernetes documentation.

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Using an annotation

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Using a Secret

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Using a PersistentVolume

Question 9

You have a Pod with a container that runs a web server. The Pod has a memory request of 256Mi and a memory limit of 512Mi. The container attempts to allocate 600Mi of memory. What happens?

Accepted Answer

The container is killed by the OOM killer, and the Pod enters CrashLoopBackOff. When a container's memory usage exceeds its memory limit (512Mi), the Linux Out-Of-Memory (OOM) killer terminates the container process. Kubernetes then restarts the container based on the Pod's restart policy, but because the container immediately tries to allocate 600Mi again, it is repeatedly killed, resulting in a CrashLoopBackOff state. Memory limits are hard constraints enforced by the kernel via cgroups, not soft limits.

Answer

The memory limit is automatically increased to 600Mi

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The Pod is evicted from the node

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The container is allowed to use up to 600Mi because the limit is a soft constraint

Question 10

A pod is stuck in 'Pending' state. 'kubectl describe pod' shows '0/4 nodes are available: 4 node(s) had taint {node.kubernetes.io/unreachable: }, that the pod didn't tolerate.' What is the most likely cause?

Accepted Answer

All nodes are unreachable or have been cordoned.. The taint `node.kubernetes.io/unreachable` is automatically added by the node controller when a node becomes unreachable (e.g., network failure, kubelet stops heartbeating). The error shows all 4 nodes have this taint and the pod has no matching toleration, meaning the scheduler cannot place the pod. This directly indicates all nodes are unreachable or have been cordoned (which also adds the `node.kubernetes.io/unschedulable` taint, but here the specific taint is `unreachable`).

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All nodes have disk pressure.

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The pod has a toleration that matches the taint.

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The nodes do not have enough CPU or memory.