CKA Practice Question 8: Pod Pending Scheduling Failure
Certified Kubernetes Administrator (CKA) · Test 1 · question 8 of 10
A newly created Pod stays in the Pending phase. Running kubectl describe pod on it shows the following event:
0/4 nodes are available: 1 node(s) had untolerated taint {node-role.kubernetes.io/control-plane: }, 3 Insufficient memory.
What is the appropriate action?
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Answer:
The event message accounts for all four nodes and explains each rejection. One node is a control plane node carrying the standard node-role.kubernetes.io/control-plane taint, which the Pod does not tolerate. The other three, the actual workers, rejected the Pod for Insufficient memory, meaning the Pod's memory request exceeds the allocatable memory still unreserved on each of them. Lowering the request to something the cluster can satisfy, or adding a node, is the real fix.
Note that the scheduler compares requests against allocatable capacity, not against current usage, so a node can report low actual memory consumption and still refuse the Pod.
Option A misreads the problem as a node registration fault. The nodes are registered and reporting capacity correctly; that is precisely how the scheduler produced this message.
Option B changes nothing. The scheduler continuously retries a Pending Pod against the cluster, so a recreated Pod meets exactly the same constraints and returns to Pending.
Option C would let the Pod run on the control plane node, but running application workloads on a control plane node is what that taint exists to prevent; it puts the Pod in contention with the API server and etcd. It treats the symptom while leaving the cluster short of worker capacity.
Reference: Debug Pods