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Kubernetes Troubleshooting Guide

While working with Kubernetes on OKE (Oracle Kubernets Engine), I encountered many issues, so I decided to create a troubleshooting guide to help identify and resolve common problems in Kubernetes deployments. 🌟🌟🌟

  • Pod issues (e.g., CrashLoopBackOff, ImagePullBackOff)
  • Service misconfigurations
  • Ingress connectivity problems

Introduction

Kubernetes deployments can encounter various issues ranging from pod scheduling problems to service misconfigurations. This guide provides a systematic approach to: 🌐🌐🌐

  • Identify the root cause of issues.
  • Apply appropriate fixes.
  • Ensure a smooth deployment process.

Features

  • Step-by-Step Troubleshooting Instructions: Navigate problems systematically.
  • Command Examples: Useful Kubernetes CLI commands.

Table of Contents

  1. Introduction
  2. Troubleshooting Pods
  3. Troubleshooting Services
  4. Troubleshooting Ingress
  5. General Debugging Commands

Troubleshooting Pods

Step 1: Check Pod Status

  1. Run: 🐳🐳🐳

kubectl get pods

  1. Observe the pod's status:
  • PENDING: Move to Step 2.
  • CrashLoopBackOff: See Step 3.
  • ImagePullBackOff: Refer to Step 4.

Step 2: Check Resource Availability

  • verify if the cluster has sufficient resources: ⚙️⚙️⚙️

    kubectl describe pod <pod-name>

  • If resources are insufficient:

    • Scale up the cluster.
    • Relax ResourceQuota limits if applicable.

Step 3: Inspect CrashLoopBackOff

  1. Check logs: 🛠️🛠️🛠️

    kubectl logs <pod-name> --previous

  2. Common fixes:

    • Update Dockerfile to include CMD if missing.
    • Fix readiness or liveness probes if they are failing.

Step 4: Fix ImagePullBackOff

  1. Verify the image name and tag: 🖼️🖼️🖼️

    kubectl describe pod <pod-name>

  2. Common solutions:

    • Correct image name/tag.
    • Configure access to private registries if required.

Troubleshooting Services

Step 1: Verify Service Configuration

  1. Check if the service exposes the correct port: 🧩🧩🧩

    kubectl describe service <service-name>

  2. Ensure targetPort matches the container's containerPort.

Step 2: Debug Endpoint Connectivity

  1. Verify endpoints: 📡📡📡 ```kubectl get endpoints``
  2. If no endpoints are listed:
  3. Check if the service selector matches pod labels.
  4. Inspect pod readiness.

Step 3: Test Port Forwarding

  1. Forward a service port to localhost: 🌐🌐🌐

kubectl port-forward service/<service-name> 8080:<service-port>

  1. Verify the app's accessibility at http://localhost:8080.

Troubleshooting Ingress

Step 1: Inspect Ingress Configuration

  1. Describe ingress: 🛣️🛣️🛣️

kubectl describe ingress <ingress-name>

  1. Check serviceName and servicePort mappings.

Step 2: Verify Backend Status

  1. Ensure backends are listed: 🎯🎯🎯

kubectl get endpoints

  1. If backends are missing:
  2. Fix service configuration.
  3. Verify pod readiness and labels.

Step 3: Debug Ingress Connectivity

  1. Forward ingress port to localhost: 🚀🚀🚀

kubectl port-forward <ingress-pod-name> 8080:<ingress-port>

  1. Test access at http://localhost:8080.

General Debugging Commands

Inspect Pod Logs

  • Current logs: 📜📜📜

    kubectl logs <pod-name>

  • Previous logs: 🔍🔍🔍

    kubectl logs <pod-name> --previous

Describe Resources

  • Pod details: 📄📄📄

    kubectl describe pod <pod-name>

  • Service details: 🛠️🛠️🛠️

    kubectl describe service <service-name>

  • Ingress details: 🌉🌉🌉

    kubectl describe ingress <ingress-name>

Contributions

We welcome contributions! Please open an issue or submit a pull request to help improve this guide.

References