Kubernetes is powerful, but it's not without its challenges. As a DevOps engineer, you’ll likely encounter a few common errors that can disrupt your workflow. Below is a simple, easy-to-understand breakdown of these issues and how to fix them.
What it is:
Your container keeps crashing and Kubernetes tries restarting it, but it can’t recover. The container starts and stops repeatedly.
Possible causes:
- Misconfigured environment variables or app settings.
- Missing dependencies.
- Not enough resources (CPU, memory).
- Bugs in your app causing it to crash.
How to fix it:
- Check logs with
kubectl logs <pod-name>. - Review your resource requests and make sure your Pod has enough CPU and memory.
- Verify environment variables and settings.
What it is:
Kubernetes can’t pull the Docker image for your container. The application won’t start because the image is unavailable.
Possible causes:
- Incorrect image name or tag.
- Private registry credentials missing or incorrect.
- Network issues preventing access to the image registry.
How to fix it:
- Double-check the image name and tag.
- Verify that Kubernetes has proper credentials for your private registry.
- Test if you can pull the image manually (
docker pull <image-name>).
What it is:
Your Pod is stuck in the "Pending" state and won’t start.
Possible causes:
- Insufficient resources on the available nodes (CPU, memory).
- Resource requests for the Pod are too high.
- Node affinity or other scheduling issues.
How to fix it:
- Use
kubectl describe nodeto check resource availability. - Lower your Pod’s resource requests to fit available nodes.
- Ensure your Pod is allowed to run on the available nodes.
What it is:
A volume (like a persistent storage volume) can’t be mounted to your Pod.
Possible causes:
- No available Persistent Volume (PV) matching the claim.
- Incorrect permissions or storage class settings.
- Volume misconfiguration in your YAML files.
How to fix it:
- Ensure the Persistent Volume (PV) matches your Persistent Volume Claim (PVC).
- Check permissions and storage class for the volume.
- Verify your volume configuration in the deployment files.
What it is:
A node in your Kubernetes cluster is marked as "Not Ready," meaning it can’t run any Pods.
Possible causes:
- Network issues or loss of connectivity.
- Resource exhaustion (out of CPU or memory).
- Issues with the Kubernetes components like Kubelet not running.
How to fix it:
- Use
kubectl describe node <node-name>to check the status of the node. - Resolve any resource issues or overloading on the node.
- Check the Kubelet logs (
journalctl -u kubelet) to diagnose issues with the node.
What it is:
Your service is unreachable, returning a "503 Service Unavailable" error. This typically happens with Ingress controllers or Load Balancers.
Possible causes:
- Misconfigured Ingress or incorrect service routing.
- Backend services or Pods not responding.
- DNS or routing issues.
How to fix it:
- Check your Ingress resource with
kubectl describe ingress <ingress-name>. - Ensure backend services (Pods) are healthy with
kubectl get pods. - Review DNS and routing configurations for errors.
What it is:
You’ve exceeded the resource limits (CPU, memory, storage) set for your namespace, so no new Pods can be created.
Possible causes:
- The namespace has reached its resource limits.
- Unused resources are consuming quota space.
How to fix it:
- Check the current quota usage with
kubectl describe quota. - Free up resources or adjust the limits to allow for more resources to be used.
- Delete unnecessary resources in the namespace to free up space.
What it is:
Kubernetes logs from the Kubelet and other components are filling up disk space, potentially causing system instability.
Possible causes:
- Logs aren’t being rotated, accumulating over time.
- High error rates or debug-level logs are being written frequently.
How to fix it:
- Set up log rotation with tools like Fluentd or Logrotate.
- Monitor disk space usage and clear unnecessary logs regularly.
What it is:
The Kubernetes API server is receiving too many requests and starts throttling, causing delays or dropped requests.
Possible causes:
- Excessive or inefficient API calls from automation or other tools.
- The API server is running out of resources (CPU, memory).
How to fix it:
- Optimize your automation tools to reduce unnecessary API calls.
- Monitor the API server’s resource usage with
kubectl top nodesand adjust resource limits.
What it is:
Kubernetes evicts (removes) Pods from a node due to resource pressure, such as running out of memory or disk space.
Possible causes:
- Resource exhaustion (like running out of memory or disk space).
- Pods exceeding their defined resource limits.
How to fix it:
- Check the eviction reason with
kubectl describe pod <pod-name>. - Adjust resource requests and limits to prevent eviction.
- Use
kubectl top nodesto monitor resource usage and prevent overloading.