Troubleshooting Common K8s Issues
Develop skills to diagnose and resolve common problems encountered when deploying and managing applications on Kubernetes.
Troubleshooting Common K8s Issues is a free Docker & Kubernetes for Developers lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Docker & Kubernetes for Developers learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
K8s Troubleshooting Overview
Kubernetes is powerful, but things can go wrong! Understanding how to diagnose issues is a vital skill for any developer or operator.
This lesson will equip you with essential tools and techniques to identify and resolve common problems in your Kubernetes clusters.
Your Primary Tool: `kubectl`
The kubectl command-line tool is your primary interface for interacting with a Kubernetes cluster. It's indispensable for troubleshooting.
- Inspect: View the status and details of your resources.
- Monitor: Check logs and events for clues.
- Interact: Run commands inside your containers for deeper debugging.
Deep Dive with `kubectl describe`
kubectl describe provides a wealth of information about a specific resource, such as a Pod, Deployment, or Service.
It shows current status, configurations, resource limits, and crucially, recent events related to that resource. Look for warnings or errors in the "Events" section.
kubectl describe pod my-app-pod-xyzChecking Application Logs
Application logs are often the first place to look when a container isn't behaving as expected. Use kubectl logs to see what your application is outputting.
# View logs for a pod
kubectl logs my-app-pod-xyz
# Follow logs in real-time
kubectl logs -f my-app-pod-xyz
# View logs from a previous instance
kubectl logs -p my-app-pod-xyzUnderstanding Cluster Events
Kubernetes generates events for significant occurrences, like Pod scheduling, image pulling, or volume mounting. These events are crucial for understanding the cluster's actions.
Use kubectl get events to see a timeline of what's happening. Filter by namespace or resource for relevance.
kubectl get events --field-selector type!=NormalInteracting with Running Containers
Sometimes you need to go inside a running container to debug. kubectl exec lets you run commands directly within a container, like checking file paths or network connectivity.
# Open a shell in a container
kubectl exec -it my-app-pod-xyz -- sh
# Run a specific command
kubectl exec my-app-pod-xyz -- ls -l /appPods Stuck in `Pending` or `CrashLoopBackOff`
These are two very common Pod status issues:
- Pending: Often due to insufficient resources (CPU/memory), node affinity issues, or a missing Persistent Volume Claim. Check
kubectl describe podevents. - CrashLoopBackOff: The container starts, crashes, and Kubernetes tries to restart it repeatedly. This usually means an application error. Check
kubectl logs.
Debugging Network Connectivity
Is your application unreachable? Network issues are common. Check these:
- Service Endpoints: Use
kubectl describe service your-serviceto ensure it has active Pod endpoints. - Ingress Rules: For external access, verify your Ingress resource rules and the Ingress controller's status.
- Network Policies: Ensure no Network Policy is blocking traffic unintentionally.
Resource Limits & OOMKilled
If your Pods are consuming too much CPU or memory, Kubernetes might terminate them. For memory, this is often seen as OOMKilled (Out Of Memory Killed).
Check your Pod's resource requests and limits in its YAML definition. Use kubectl describe pod to see if a container was OOMKilled.
Quick Check: Debugging Steps
You've deployed a new Pod, but it's stuck in Pending status. What are the most likely first steps you should take to diagnose the problem?
K8s Troubleshooting Recap
You've learned to approach Kubernetes troubleshooting systematically. Remember your key tools:
kubectl describefor detailed resource info and events.kubectl logsfor application output.kubectl get eventsfor cluster-wide occurrences.kubectl execfor in-container debugging.
Practice these commands to quickly pinpoint and resolve issues in your Kubernetes deployments!
Frequently asked questions
Is the “Troubleshooting Common K8s Issues” lesson free?
Yes — the full text of “Troubleshooting Common K8s Issues” is free to read here on the web, and the Docker & Kubernetes for Developers course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Docker & Kubernetes for Developers course, upgrade to CoddyKit PRO.
What will I learn in “Troubleshooting Common K8s Issues”?
Develop skills to diagnose and resolve common problems encountered when deploying and managing applications on Kubernetes. You practise Docker & Kubernetes for Developers with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Docker & Kubernetes for Developers?
No prior experience is required. Docker & Kubernetes for Developers on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Troubleshooting Common K8s Issues” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Docker & Kubernetes for Developers lesson?
Yes. Every Docker & Kubernetes for Developers lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Kubernetes Logging Strategies
- Monitoring with Prometheus & Grafana
- Troubleshooting Common K8s Issues
- Health Checks: Liveness, Readiness, and Startup Probes