How to Fix Kubernetes CrashLoopBackOff: A Practical Guide

It’s the most famous (and frustrating) status in the Kubernetes world. You run kubectl get pods, and there it is: 0/1 CrashLoopBackOff.

Despite the scary name, CrashLoopBackOff isn’t actually the error—it’s Kubernetes telling you: "I tried to start your app, it died, I waited, and I’m about to try again."

Here is the "Triple Post" finale to get your cluster healthy before the weekend.

---

1. The "First 3" Commands

Before you start guessing, run these three commands in order. They tell you 90% of what you need to know.

Command	Why run it?
kubectl describe pod <name>	Look at the Events section at the bottom. It often says why it failed (e.g., OOMKilled).
kubectl logs <name> --previous	Crucial. This shows the logs from the failed instance before it restarted.
kubectl get events --sort-by=.metadata.creationTimestamp	Shows a timeline of cluster-wide issues (like Node pressure).

2. The Usual Suspects

If the logs are empty (a common headache!), the issue is likely happening before the app even starts.

• OOMKilled: Your container exceeded its memory limit.

  • Fix: Increase resources.limits.memory.

• Config Errors: You referenced a Secret or ConfigMap that doesn't exist, or has a typo.

  • Fix: Check the describe pod output for "MountVolume.SetUp failed".

• Permissions: Your app is trying to write to a directory it doesn't own (standard in hardened images).

  • Fix: Check your securityContext or Dockerfile USER permissions.

• Liveness Probe Failure: Your app is actually running fine, but the probe is checking the wrong port.

  • Fix: Double-check livenessProbe.httpGet.port.

---

3. The Pro-Tip: The "Sleeper" Debug

If you still can't find the bug because the container crashes too fast to inspect, override the entrypoint.

Update your deployment YAML to just run a sleep loop:

command: ["/bin/sh", "-c", "while true; do sleep 30; done;"]

Now the pod will stay "Running," and you can kubectl exec -it <pod> -- /bin/sh to poke around the environment manually!