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Debugging in Kubernetes

Kubernetes is great for managing complex applications. Unfortunately, though, even in the best circumstances, problems can still occur. Therefore, debugging is an important skill when it comes to managing Kubernetes applications in practice. This lab will give you an opportunity to practice some common Kubernetes debugging skills, such as obtaining important debugging info and locating problems within the cluster.

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Path Info

Clock icon Intermediate
Clock icon 1h 30m
Clock icon Mar 31, 2019

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Table of Contents

  1. Challenge

    Find the broken pod and save the pod name to the file `/home/cloud_user/debug/broken-pod-name.txt`

    Since you don't know what namespace the broken pod is in, a quick way to find the broken pod is to list all pods from all namespaces:

    kubectl get pods --all-namespaces

    Check the STATUS field to find which pod is broken. Once you have located the broken pod, vi /home/cloud_user/debug/broken-pod-name.txt, enter the name of the broken pod, and save the file.

  2. Challenge

    In the same namespace as the broken pod, find out which pod is using the most CPU and output the name of that pod to the file `/home/cloud_user/debug/high-cpu-pod-name.txt`

    Look at the namespace of the broken pod, and then use kubectl top pod to show resource usage for all pods in that namespace.

    kubectl top pod -n <NAMESPACE>

    Identify which pod in that namespace is using the most CPU, then vi /home/cloud_user/debug/high-cpu-pod-name.txt, enter the name of the pod with the highest CPU usage, and then save the file.

  3. Challenge

    Get the broken pod's summary data in the JSON format and output it to the file `/home/cloud_user/debug/broken-pod-summary.json`

    You can get the JSON data and output it to the file like this:

    kubectl get pod <POD_NAME> -n <NAMESPACE> -o json > /home/cloud_user/debug/broken-pod-summary.json
  4. Challenge

    Get the broken pod's container logs and output them to the file `/home/cloud_user/debug/broken-pod-logs.log`

    You can get the logs and output them to the file like this:

    kubectl logs <POD_NAME> -n &ltnamespace> > /home/cloud_user/debug/broken-pod-logs.log
  5. Challenge

    Fix the problem with the broken pod so that it enters the `Running` state

    Describe the broken pod to help identify what is wrong:

    kubectl describe pod <POD_NAME> -n <NAMESPACE>

    Check the Events to see if you can spot what is wrong.

    You may notice the pod's liveness probe is failing. If you look closely, you might also notice the path for the liveness probe looks like it may be incorrect.

    In order to edit and fix the liveness probe, you will need to delete and recreate the pod. You should save the pod descriptor before deleting it, or you will have no way to recover it!

    kubectl get pod <POD_NAME> -n <NAMESPACE> -o yaml --export > broken-pod.yml

    Delete the broken pod:

    kubectl delete pod <POD_NAME> -n <NAMESPACE>

    Now, edit the descriptor file, and fix the path attribute for the liveness probe: vi broken-pod.yml.

    Recreate the broken pod with the fixed probe:

    kubectl apply -f broken-pod.yml -n <NAMESPACE>

    Check to make sure the pod is now running properly:

    kubectl get pod <POD_NAME> -n <NAMESPACE>

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