Application

Exercise 🔗

This exercise covers common application failure scenarios.

ImagePullBackOff Issues 🔗

1. Create a Pod with an invalid image name, check the Pod status and describe it.

kubectl run broken-image --image=nginx:nonexistent-tag

2. Fix the image reference using an existing image

CrashLoopBackOff Issues 🔗

3. Create a Pod that exits immediately

kubectl run crash-pod --image=busybox --command -- /bin/sh -c "exit 1"

4. Examine the logs and fix the Pod to keep it running

Documentation 🔗

• https://kubernetes.io/docs/tasks/debug/debug-application/debug-pods/
• https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/

Solution 🔗

ImagePullBackOff Issues 🔗

1. Create a Pod with an invalid image name, check the Pod status and describe it.

• creating the Pod

kubectl run broken-image --image=nginx:nonexistent-tag

• checking the Pods status shows ImagePullBackOff

kubectl get pod broken-image

• describing the Pod gives the origin of the error (image cannot be pulled)

kubectl describe pod broken-image

2. Fix the image reference using an existing image

kubectl delete pod broken-image
kubectl run broken-image --image=nginx:latest

CrashLoopBackOff Issues 🔗

3. Create a Pod that exits immediately

Command provided in the instructions

4. Examine the logs and fix the Pod to keep it running

• getting the Pod shows an CrashLoopBackOff error

kubectl get pods crash-pod

• the logs don’t provide any information

kubectl logs crash-pod

• describing the Pod shows the exit status 1

kubectl describe pod crash-pod

• fixing the specification using another command

kubectl delete pod crash-pod
kubectl run crash-pod --image=busybox --command -- /bin/sh -c "while true; do sleep 30; done"