CKA Troubleshooting Practice Question
After deploying a new Deployment, you run 'kubectl get events' and see 'FailedScheduling' events. What is a possible cause?
⚠ Common exam trap
Many candidates confuse scheduling failures with runtime failures, as candidates often associate port conflicts or image pull issues with scheduling, when in fact those errors occur after the pod is placed on a node.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The pod has a node selector that matches no nodes
A FailedScheduling event indicates that the Kubernetes scheduler could not find a suitable node to place the pod. Option B is correct because if a pod has a node selector that does not match any node's labels, the scheduler will fail to schedule it, resulting in a FailedScheduling event. The scheduler evaluates node selectors against node labels, and if no node satisfies the selector, the pod remains unscheduled.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The container port is already in use on the node
Why it's wrong here
If a container port or host port conflict occurs, the Kubernetes scheduler may still assign the pod to a node. Once assigned, the container runtime on the node will fail to bind to the port, leading to a container crash and a CrashLoopBackOff status rather than a FailedScheduling event.
- ✓
The pod has a node selector that matches no nodes
Why this is correct
When a pod defines a nodeSelector that does not match the labels of any active node in the cluster, the default-scheduler cannot find a valid placement. Consequently, the pod remains in a Pending state, and the scheduler emits a FailedScheduling warning event indicating that zero nodes match the selector.
- ✗
The node has a taint that tolerates the pod
Why it's wrong here
Taints and tolerations work together to ensure pods are not scheduled onto inappropriate nodes. If a node has a taint but the pod has a matching toleration, the scheduler is permitted to place the pod on that node, meaning this configuration would facilitate successful scheduling rather than causing a scheduling failure event.
- ✗
The pod's image pull secret is missing
Why it's wrong here
A missing image pull secret is an execution-phase issue that occurs after the pod has already been successfully scheduled to a node. The local kubelet attempts to pull the container image, fails due to authentication issues, and generates ErrImagePull and ImagePullBackOff events, rather than a scheduler-level failure.
Go deeper
Related to this question
Learn chapter
Troubleshooting Cluster and Node Issues
Key term
Network Policies
A Kubernetes resource that controls how pods communicate with each other and with other network endpoints, acting as a firewall for pod-to-pod traffic.
Key term
Ingress Resources
Ingress Resources are Kubernetes API objects that manage external access to services inside a cluster, typically HTTP and HTTPS traffic, by defining rules for routing requests based on hostnames and paths.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKA exam.