A pod remains Pending before its containers are running. It may be unscheduled because no node satisfies its requirements, or scheduled but waiting for volumes, image sandbox setup, or another node-level dependency.

Read scheduler events first

kubectl describe pod POD -n NAMESPACE
kubectl get events -n NAMESPACE --sort-by=.lastTimestamp

FailedScheduling messages usually state how many nodes were rejected and why: insufficient resources, taints, affinity rules, topology constraints, or unbound volumes.

Compare requests with available capacity

kubectl get pod POD -n NAMESPACE -o jsonpath='{.spec.containers[*].resources}'
kubectl describe nodes
kubectl top nodes

Scheduling uses resource requests and allocatable capacity, not only current utilization shown by top.

Check scheduling constraints

Inspect:

nodeSelector and node affinity
pod anti-affinity
topology spread constraints
node taints and pod tolerations
required host ports
RuntimeClass requirements

kubectl get pod POD -n NAMESPACE -o yaml
kubectl get nodes --show-labels

Do not remove a taint or weaken affinity globally before understanding why the constraint exists.

Check volumes and quotas

kubectl get pvc -n NAMESPACE
kubectl describe pvc CLAIM -n NAMESPACE
kubectl get resourcequota,limitrange -n NAMESPACE

An unbound claim, unavailable storage class, or namespace quota can prevent progress.

Diagnose it with Rumus

Diagnose why this pod is Pending. Inspect scheduler events, resource requests and
allocatable capacity, taints and tolerations, affinity, topology constraints,
host ports, PVCs, quotas, and node conditions. Rank the causes using observed
evidence and do not modify cluster constraints without approval.

Confirm the fix

After correcting the owning workload or cluster capacity:

kubectl get pod POD -n NAMESPACE -w
kubectl describe pod POD -n NAMESPACE

Confirm that the pod receives a node assignment and progresses beyond Pending without new warning events.

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