12 kubectl commands and 23 causes in 5 categories - with a decision tree and a concrete fix per pattern. Printable, free, no signup.
kubectl describe pod <name> | tail -20→ The Events section at the end - literally tells you what is wrong.
kubectl get events --field-selector reason=FailedScheduling -A --sort-by=.lastTimestamp | tail -20→ Every scheduling problem cluster-wide, sorted by time.
kubectl get pods -A --field-selector=status.phase=Pending→ Find every Pending pod at a glance.
kubectl describe node <node> | grep -A 8 "Allocated resources"→ Total requests vs capacity - reveals over-provisioned nodes.
kubectl top nodes→ Current usage per node - the fastest resource scan.
kubectl get pod <name> -o jsonpath='{range .spec.containers[*]}{.name}: {.resources.requests}{"\n"}{end}'→ What the pod is asking for - often the unrealistic root cause.
kubectl get nodes --show-labels→ For nodeSelector and affinity mismatch diagnosis.
kubectl describe nodes | grep -A 1 "Taints:"→ Which nodes carry taints - who lacks a toleration.
kubectl describe node <node> | grep -A 10 "Conditions"→ DiskPressure, MemoryPressure, NotReady at a glance.
kubectl get pvc -A | grep -v Bound→ Every non-Bound PVC - classic source of Pod Pending.
kubectl get sc→ Which StorageClasses exist - is one marked default?
kubectl describe pod <name> | grep -A 3 "Failed\|ErrImagePull\|InvalidImage"→ Image issues extracted from the Events section.
Complete listing across 5 categories with a quick-check per pattern.
Insufficient CPU
describe node → Allocated CPU
Insufficient Memory
describe node → Allocated Memory
Insufficient ephemeral-storage
describe node → ephemeral-storage
Requests > node capacity
Container requests > max node spec
NodeSelector mismatch
kubectl get nodes -l <selector> empty
NodeAffinity (required)
Events: didn't match Pod's node affinity
Taint without toleration
Events: node had untolerated taint
PodAntiAffinity
Events: didn't satisfy anti-affinity
TopologySpreadConstraints
Events: skew exceeds maxSkew
Pod topology DoNotSchedule
Events: pod topology
PVC not Bound
kubectl get pvc | grep -v Bound
PVC RWO already mounted
Events: Multi-Attach error
Volume topology conflict
Events: volume node affinity conflict
StorageClass missing
kubectl get sc
ImagePullBackOff
Events: Failed to pull image
ErrImagePull
Events: Error: ErrImagePull
InvalidImageName
Events: InvalidImageName
Missing imagePullSecrets
Events: pull access denied
NodeNotReady
kubectl get nodes → NotReady
DiskPressure
describe node → Conditions
MemoryPressure / PIDPressure
describe node → Conditions
ResourceQuota exceeded
Events: exceeded quota
LimitRange violation
Events: minimum cpu usage violated
→ Lower requests or scale the cluster → Add tolerations: to the pod → Check StorageClass + provisioner → volumeBindingMode: WaitForFirstConsumer → Check imagePullSecrets Replay real production incidents, internalise kubectl workflows, find root causes in minutes.
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