Kubernetes Pod Stuck in CrashLoopBackOff

CrashLoopBackOff is not the error — it is Kubernetes giving up on restarting a container that keeps dying. The real error is in the previous container's logs.

What you'll see

Root causes

App fails on startup

Bad env var, missing secret, unreachable dependency, or a config syntax error. The process exits 1 immediately.

Liveness probe too aggressive

Probe kills the container before the app finishes booting — classic for JVM and Rails apps with slow warmup.

OOMKilled inside the pod

Container exceeds its memory limit and gets SIGKILLed. Last State in describe shows Reason: OOMKilled.

Fix it

  1. Read the logs of the previous (crashed) container
    kubectl logs <pod> --previous --tail=100
  2. Check the events and last state
    kubectl describe pod <pod> | grep -A6 'Last State'
  3. For probe kills, add a startupProbe or raise delays
    startupProbe:
  httpGet: { path: /healthz, port: 8080 }
  failureThreshold: 30
  periodSeconds: 5
  4. For config errors, fix the env/secret, then restart
    kubectl rollout restart deployment/<name>

Field note

A pattern of exit code 1 within a second of start is almost always config. A container that runs fine for minutes then dies points at memory or a runtime crash — pull the previous logs before changing anything.

Common questions

Why does the pod keep restarting instead of just failing?

A restartPolicy of Always (the default) makes the kubelet retry failed containers with exponential backoff — CrashLoopBackOff is the backoff state, not a separate error. The real failure is in the container logs of the previous attempt.

How do I see logs from a crashing container?

kubectl logs <pod> --previous shows the last crashed attempt — the one whose exit started the backoff. Without --previous you may catch the current attempt before it dies, or nothing at all.

Related fixes

Ship it right the first time

Kustomize base with probes, PDBs, and zero-downtime rollouts already wired.

Kubernetes Production Blueprints — $27 →

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