CKAD Application Observability and Maintenance Practice Question
You run 'kubectl get events' and see an event 'FailedScheduling' for a pod. What is the most common cause?
⚠ Common exam trap
Test-takers frequently confuse 'FailedScheduling' with pod runtime failures (like image pull or probe failures), but scheduling events occur before the pod is bound to a node, so only resource-related or node affinity issues apply.
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
✓
Insufficient node resources to meet the pod's requests
The 'FailedScheduling' event indicates that the Kubernetes scheduler could not find a suitable node to place the pod. The most common cause is insufficient node resources (CPU, memory, or ephemeral storage) to meet the pod's resource requests defined in the pod spec. The scheduler uses the `kube-scheduler` component to evaluate node fit based on predicates like `PodFitsResources`, and if no node satisfies the requested resources, the pod remains in a Pending state with this event.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Insufficient node resources to meet the pod's requests
Why this is correct
The FailedScheduling event is emitted by the kube-scheduler when no node passes all scheduling predicates for the pod. For a plain resource shortage, the scheduler cannot find a node with enough allocatable CPU/memory to meet the sum of container requests (not limits). This can also be triggered by node selectors, taints/tolerations, or affinity rules excluding every node, but the most common cause is insufficient resources. The event message typically names the specific constraint, such as 'Insufficient memory', for the node(s) attempted.
- ✗
The pod's container image pull failed
Why it's wrong here
Image pull failures occur during the kubelet's container creation phase after a node has already been selected and the pod is bound. The kubelet emits events like ErrImagePull or BackOff on the pod, and the container may show ImagePullBackOff in status. FailedScheduling, in contrast, is emitted solely by the scheduler before any node is assigned. Therefore, an image pull problem cannot generate a FailedScheduling event.
- ✗
The liveness probe failed
Why it's wrong here
Liveness probes are executed by the kubelet on containers that are already running on an assigned node. When a liveness probe fails, the kubelet restarts the container and emits events such as Unhealthy or Killing on the pod, and the pod may enter CrashLoopBackOff. Since this occurs after scheduling, it never produces a FailedScheduling event, which only exists in the pre-binding scheduling phase.
- ✗
The pod was deleted by a Deployment update
Why it's wrong here
A Deployment update causes the controller to terminate old ReplicaSet pods and create new ones; the old pods are deleted gracefully, generating normal delete and termination events. While the replacement pods might later fail to schedule for independent reasons, the deletion action itself is not a scheduling event. FailedScheduling appears only if the scheduler cannot place one of the new pods, which is not caused by the update operation itself but by node capacity or constraints at that moment.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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