How Do You Troubleshoot the Kubernetes Pods Error “CrashLoopBackOff”?

Problem scenario
You have a problem with Pods not starting up. They have a status of "CrashLoopBackOff". What should you do?

Possible Solution #1
Can the Pods start in a lower environment with minimal utilization? Being able to reproduce the problem can help. Trying the YAML in an optimal environment can help you pinpoint the error (e.g., traffic may be high in a production environment). Verifying the deployment dependencies are all met can lead to a better understanding of what precisely is needed.

Possible Solution #2
Look at your monitoring of the Pods and relevant nodes. Are the CPU, RAM and disk utilizations looking healthy? Did it used to work? What changed to make it now not work? If it never worked, you should revise your YAML file or look at the image you are using.

Possible Solution #3
Run this command on a Pod with the status "CrashLoopBackOff": kubectl describe foobar #where "foobar" is the name of the Pod
kubectl logs foobar --all-containers # replace "foobar" with the name of your Pod
Run this command: kubectl get events

This possible solution was influenced by

Possible Solution #4
Increase the memory given to the Pods (e.g., in the relevant YAML file).

Possible Solution #5
Is the Pod trying to use a PersistentVolume?

Can you view the logs of the Pod? Are there other details about what could be wrong? Can you view the Deployment logs? If the Pod is coming up, can you enter it and try to figure out what is wrong with the CrashLoopBackOff and/or Persistent Volume?

See also
How Do You Troubleshoot a PVC That Appears to Still Be in Use?

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