Debug Kubernetes Part 1

Debugging steps for CrashLoopBackOff issue.

CrashLoopBackOff is a common Kubernetes error which indicates a pod that is constantly crashing in an endless loop.

Common Causes:

  • Insufficient resources
  • Issues with init-container setup
  • Misconfigurations
  • Deploying failed services / apps
  • Locked file / database
  • Unable to load the config file
  • Connection issues
  • Failed references

Troubleshooting:

1. Check for “Back Off Restarting Failed Container”
 $ kubectl describe pod [name].

2. Search the Logs From Previous Container Instance
 $ kubectl logs –previous –tail 10

3. Check kubectl Deployment Logs
 $ kubectl logs -f deploy/ -n

4. Access the CrashLoop container to identify the issue
Step 1: Locate the entrypoint and cmd for the container image
 $ docker pull [image-id] to pull the image.
 $ docker inspect [image-id]

Step 2: Change entrypoint
Since the container has crashed and couldn’t start, we need to temporarily change the entrypoint to tail -f /dev/null.

Step 3: Install debugging tools (e.g. curl or vim) if its not there already
 $ sudo apt-get install [name of debugging tool]

Step 4: Check for missing packages or dependencies
Step 5: Check application configuration
e.g. Inspecting environment variables and the credentials of the database configuration file.

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