Module #48 · beginner Article
Pod Lifecycle States: Phase Transitions from Pending to Running and Termination
A pod moves through: Pending → Running → Succeeded/Failed, with sub-states like CrashLoopBackOff, ImagePullBackOff, and OOMKilled visible in the container st...
4 min read+10 XPPublished 2026-07-08
Quick Answer: A pod moves through: Pending → Running → Succeeded/Failed, with sub-states like CrashLoopBackOff, ImagePullBackOff, and OOMKilled visible in the container status.
Detailed Answer:
Pod Phases (high level):
├── Pending — Accepted by API server but not yet running
│ Reasons: scheduling (no node), image pull, PVC binding
├── Running — At least one container is running
├── Succeeded — All containers exited with code 0 (Jobs/CronJobs)
├── Failed — At least one container exited with non-zero code
└── Unknown — Node communication lost (node down)
Container States (granular — inside a running/pending pod):
├── Waiting — Not yet running; reason tells you why:
│ ├── ContainerCreating — Image being pulled
│ ├── ImagePullBackOff — Can't pull image (bad tag, auth failure)
│ ├── ErrImagePull — Pull failed
│ ├── CrashLoopBackOff — Keeps crashing (exponential backoff)
│ └── CreateContainerConfigError — Bad env var, missing secret/configmap
├── Running — Container is executing
└── Terminated — Container exited; reason:
├── Completed — Exit code 0
├── Error — Non-zero exit code
└── OOMKilled — Exceeded memory limit
# See pod phase
kubectl get pod my-pod -o jsonpath='{.status.phase}'
# See container state and reason
kubectl get pod my-pod -o jsonpath='{.status.containerStatuses[0].state}'
# Most informative — always check this first
kubectl describe pod my-pod | tail -30 # Events section at bottom
Debugging by State:
- Pending:
describe pod→ check Events for "Insufficient CPU/memory", "no nodes match selector", "unbound PVC" - CrashLoopBackOff:
logs --previous→ what was the app printing before it died? - ImagePullBackOff: Check image name, tag, registry credentials
Key Takeaway: The container state reason (CrashLoopBackOff, OOMKilled, ImagePullBackOff) is more informative than the pod phase — always look at kubectl describe pod Events and kubectl logs --previous for root cause.
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