Troubleshooting Kubernetes: Common Issues and Solutions

Details: Category: DevOps Tools; By Mindful Chase; 28.Feb; Hits: 3

Kubernetes is a powerful container orchestration platform that automates deployment, scaling, and operations of application containers. However, users often encounter issues such as pod failures, networking misconfigurations, storage issues, resource limits, and cluster instability. This article explores common troubleshooting scenarios in Kubernetes, their root causes, and effective solutions.

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1. Pods Stuck in Pending or CrashLoopBackOff

Understanding the Issue

Pods fail to start or repeatedly restart, causing application downtime.

Root Causes

Insufficient resources (CPU, memory) on nodes.
Missing or incorrect container images.
Volume mounting failures.

Fix

Check pod status and events:

kubectl get pods -n mynamespace

Describe the pod for more details:

kubectl describe pod mypod -n mynamespace

Inspect container logs for errors:

kubectl logs mypod -n mynamespace --previous

Ensure the container image is available:

kubectl get pod mypod -o=jsonpath='{.spec.containers[*].image}'

2. Kubernetes Service Not Accessible

Understanding the Issue

Applications cannot reach Kubernetes services, causing connectivity failures.

Root Causes

Incorrect service type or selector.
Networking issues with kube-proxy or CNI plugin.
Missing endpoints in service configuration.

Fix

Check service and endpoints:

kubectl get svc myservice -n mynamespace

kubectl get endpoints myservice -n mynamespace

Ensure pods are correctly labeled:

kubectl get pods --show-labels -n mynamespace

Restart kube-proxy to resolve networking issues:

kubectl rollout restart daemonset/kube-proxy -n kube-system

3. Persistent Volume (PV) and Persistent Volume Claim (PVC) Failures

Understanding the Issue

Pods cannot access persistent storage due to unbound volumes.

Root Causes

Misconfigured StorageClass.
Insufficient storage capacity.
Incorrect PVC-PV binding.

Fix

Check PVC status:

kubectl get pvc -n mynamespace

Describe the PVC for more details:

kubectl describe pvc mypvc -n mynamespace

Ensure StorageClass is correctly defined:

kubectl get storageclass

4. High CPU or Memory Usage in Kubernetes Cluster

Understanding the Issue

Kubernetes nodes or pods consume excessive CPU or memory, impacting performance.

Root Causes

Unoptimized resource requests and limits.
Memory leaks in applications.
Overloaded nodes due to improper scheduling.

Fix

Check pod resource usage:

kubectl top pods -n mynamespace

Check node resource utilization:

kubectl top nodes

Set resource requests and limits in deployments:

resources:
  requests:
    cpu: "500m"
    memory: "256Mi"
  limits:
    cpu: "1"
    memory: "512Mi"

5. Cluster Nodes Not Ready

Understanding the Issue

Nodes enter the NotReady state, affecting pod scheduling and cluster stability.

Root Causes

Network plugin failures.
kubelet crashes or misconfiguration.
Insufficient node resources.

Fix

Check node status:

kubectl get nodes

Restart kubelet service on the affected node:

sudo systemctl restart kubelet

Check kubelet logs for errors:

journalctl -u kubelet -n 50 --no-pager

Conclusion

Kubernetes is a robust orchestration tool, but troubleshooting pod failures, networking issues, storage problems, resource usage, and node failures is essential for a stable and efficient cluster. By optimizing configurations, monitoring resource limits, and ensuring proper cluster setup, users can enhance Kubernetes performance and reliability.

FAQs

1. How do I fix pods stuck in CrashLoopBackOff?

Check logs with kubectl logs, ensure the container image exists, and verify resource allocations.

2. Why is my Kubernetes service not reachable?

Ensure the correct service type, check pod labels, and verify endpoints.

3. How do I resolve PVC binding issues?

Ensure the StorageClass exists, check PVC status, and verify storage capacity.

4. How do I reduce high CPU and memory usage in Kubernetes?

Set resource requests and limits, optimize application code, and distribute workloads across nodes.

5. How do I troubleshoot nodes in NotReady state?

Check kubelet logs, restart kubelet, and verify network plugin status.

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