KCNA Kubernetes Fundamentals Practice Test 6 — 15 Questions

Question 1

A developer needs to update a running Deployment's container image from 'nginx:1.21' to 'nginx:1.23' with minimal downtime and the ability to roll back if the new version fails. Which kubectl command should be used?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

kubectl set image deployment/my-deployment nginx=nginx:1.23. `kubectl set image` directly updates the container image of a running Deployment, triggering a rolling update that replaces pods gradually to minimize downtime. This command also preserves the Deployment's rollout history, enabling a simple `kubectl rollout undo` to roll back if the new image fails.

Answer

kubectl edit deployment my-deployment

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kubectl apply -f updated-deployment.yaml

Answer

kubectl patch deployment my-deployment -p '{"spec":{"template":{"spec":{"containers":[{"name":"nginx","image":"nginx:1.23"}]}}}}'

Question 2

You want to expose a set of pods running a web application on port 80 internally within the cluster, with a stable IP address, so that other services can reach them. Which Kubernetes resource should you create?

Accepted Answer

Service (ClusterIP). A Service of type ClusterIP provides a stable virtual IP address and DNS name that load-balances traffic to a set of pods. Since the requirement is internal cluster access with a stable IP, ClusterIP is the correct choice — it exposes the pods on a cluster-internal IP that other services can reach reliably, without needing external exposure.

Answer

Ingress

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Deployment

Answer

Pod

Question 3

A DevOps engineer has created a ConfigMap named 'app-config' and wants to use it to set environment variables in a pod. Which field in the pod spec should reference the ConfigMap?

Accepted Answer

spec.containers[].envFrom. `spec.containers[].envFrom` allows you to inject all key-value pairs from a ConfigMap (or Secret) as environment variables into a container in a single declaration. This field supports a `configMapRef` that references the ConfigMap by name, making it the appropriate spec field for bulk environment variable injection.

Answer

spec.containers[].command

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spec.containers[].env.name

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spec.containers[].volumeMounts

Question 4

You notice that a pod is in 'Pending' state for a long time. Which of the following is the most likely cause?

Accepted Answer

No node has enough CPU or memory to meet the pod's requests.. A pod remains in 'Pending' state when the scheduler cannot find a node that satisfies its resource requests. The most common reason is insufficient CPU or memory capacity across all available nodes, preventing the pod from being bound to a node. Unlike probe failures or missing images, which cause 'Running' or 'ImagePullBackOff' states, resource constraints block scheduling entirely.

Answer

The pod's liveness probe is failing.

Answer

The pod's readiness probe is not configured.

Answer

The container image does not exist.

Question 5

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.

Answer

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

Answer

Set spec.nodeName to the node's name.

Question 6

A developer created a Deployment with 5 replicas. After applying the manifest, only 3 pods are Running; the other 2 are Pending. Which is the MOST likely cause?

Accepted Answer

The nodes do not have enough available CPU or memory to schedule the additional pods. D is correct because when a Pod remains in Pending state, it indicates that the scheduler cannot find a node that satisfies the Pod's resource requests. Since 3 Pods are already running and consuming resources, the remaining 2 Pods cannot be placed if the cluster's nodes lack sufficient allocatable CPU or memory. This is a classic resource-constrained scheduling failure, not a runtime or network issue.

Answer

The readiness probe is failing

Answer

A NetworkPolicy is blocking traffic to the pods

Answer

The container image is misspelled

Question 7

What is the primary purpose of a Kubernetes Service?

Accepted Answer

To provide a stable network endpoint for a set of pods. A Kubernetes Service provides a stable, virtual IP and DNS name that remains constant even as the underlying pods are created, destroyed, or scaled. It acts as a load balancer across a set of pods selected by labels, abstracting away the ephemeral nature of pod IPs. This enables reliable communication between components within the cluster without requiring clients to track individual pod addresses.

Answer

To implement network routing rules on each node

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To manage rolling updates of applications

Answer

To store configuration data as key-value pairs

Question 8

Which component of the Kubernetes control plane is responsible for storing the cluster state?

Accepted Answer

etcd. etcd is the distributed key-value store that serves as Kubernetes' single source of truth for cluster state. It stores all cluster data, including configuration, desired state, and current state of objects like Pods, Services, and Deployments. The kube-apiserver is the only component that directly communicates with etcd, ensuring consistency and transactional integrity.

Answer

kube-scheduler

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kube-controller-manager

Answer

kube-apiserver

Question 9

A developer wants to deploy a stateless web application that should maintain three running instances at all times. Which Kubernetes resource should they use?

Accepted Answer

Deployment. A Deployment is the correct resource because it manages a ReplicaSet to ensure a specified number of Pod replicas (in this case, three) are running at all times. It supports rolling updates and rollbacks, making it ideal for stateless web applications that require high availability and declarative scaling.

Answer

Job

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StatefulSet

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DaemonSet

Question 10

You need to inspect the logs of a container named 'app' in a pod called 'web-1'. Which kubectl command should you use?

Accepted Answer

kubectl logs web-1 --container app. Both Option A and Option B are correct. The `kubectl logs` command supports both the short flag `-c` and the long flag `--container` to specify a container within a multi-container pod. Option A uses the long form `--container` which is fully valid, and Option B uses the short form `-c`. The argument order is correct in both: pod name first, then container flag. Option C incorrectly places the container name as the first argument (kubectl logs app web-1). Option D uses the `-p` flag, which is for viewing logs of a previous container instance, not for selecting a container by name.

Answer

kubectl logs app web-1

Answer

kubectl logs -p web-1 app

Question 11

A pod remains in 'Pending' state. Upon inspecting the pod with 'kubectl describe pod', you see the message '0/1 nodes are available: 1 node(s) had taint {node.kubernetes.io/disk-pressure: }, that the pod didn't tolerate'. What is the most likely cause?

Accepted Answer

The node has a disk pressure condition and the pod lacks a toleration. The message '0/1 nodes are available: 1 node(s) had taint {node.kubernetes.io/disk-pressure: }, that the pod didn't tolerate' indicates the node has a taint of 'disk-pressure' which prevents pod scheduling unless the pod has a matching toleration. Since the pod lacks this toleration, it remains in 'Pending' state. Option B correctly identifies the node's disk pressure condition and the missing toleration as the cause.

Answer

The pod is not using a ServiceAccount

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The pod's resource requests exceed the node's capacity

Answer

The pod's container image does not exist

Question 12

Which of the following is true about Kubernetes Namespaces?

Accepted Answer

Namespaces can help organize and manage resources in a cluster. Namespaces in Kubernetes provide a mechanism for isolating groups of resources within a single cluster. They allow you to organize resources like Pods, Services, and Deployments into logical groups, which is especially useful in multi-tenant environments or when managing different environments (e.g., dev, staging, prod) within the same cluster. This makes option A correct.

Answer

Resource names must be unique across all namespaces

Answer

Namespaces provide network isolation between resources

Answer

You must create a namespace before creating any resources

Question 13

A container in a pod has been restarted multiple times with 'CrashLoopBackOff' state. What does this indicate?

Accepted Answer

The container exits with a non-zero exit code soon after starting. The 'CrashLoopBackOff' state indicates that a container in a pod repeatedly starts, exits with a non-zero exit code, and is then restarted by the kubelet. This loop triggers an exponential backoff delay, preventing the container from staying up. The core issue is that the container process fails almost immediately after starting, not that it is resource-constrained or unresponsive.

Answer

The container is using too much memory

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The container is running but not responding to health checks

Answer

The container image cannot be pulled

Question 14

A user runs 'kubectl get pods -n production' and sees no output. What is the most likely reason?

Accepted Answer

There are no pods in the 'production' namespace. `kubectl get pods -n production` returning no output typically indicates that there are no pods in the specified namespace. The command successfully connected to the API server, authenticated, and queried the namespace, but the result set is empty. This is a common scenario when a namespace exists but has no running or pending pods.

Answer

The kube-apiserver is down

Answer

The user does not have permissions to list pods

Answer

The namespace does not exist

Question 15

Which component runs on every worker node and is responsible for maintaining the lifecycle of pods?

Accepted Answer

kubelet. The kubelet is the primary node agent that runs on every worker node in a Kubernetes cluster. It is responsible for ensuring that containers are running in a Pod as expected, by interacting with the container runtime (e.g., containerd or CRI-O) to start, stop, and monitor Pods based on PodSpecs received from the API server. Without the kubelet, the node cannot manage Pod lifecycles.

Answer

container runtime

Answer

kube-scheduler

Answer

kube-proxy