Introduction

This tutorial aims to guide you through the process of debugging Kubernetes Pods and Containers. Kubernetes, an open-source platform designed to manage containerized workloads and services, can sometimes present challenges when things go wrong. This tutorial will help you understand how to diagnose and fix common problems.

By the end of this tutorial, you will learn:

• How to diagnose issues with Kubernetes pods and containers
• How to fix common problems
• Best practices for maintaining a healthy Kubernetes environment

Prerequisites:
- Basic understanding of Kubernetes
- Familiarity with command-line interfaces
- Access to a Kubernetes environment (for practice)

Step-by-Step Guide

1. Understanding Kubernetes Pods and Containers

A Pod is the smallest, most basic deployable object in Kubernetes. It can contain one or more containers, and resources are shared among these containers.

1. Accessing Logs

Logs are invaluable when debugging issues. To access the logs for a particular pod, use the kubectl logs command:

kubectl logs <pod-name>

1. Accessing Shell Within a Container

Sometimes, you may need to access the shell within a container for troubleshooting. Use the kubectl exec command:

kubectl exec -it <pod-name> -- /bin/bash

Code Examples

1. Checking Pod Status

Use the command below to check the status of all pods:

sh kubectl get pods

This will return a list of all pods and their status. This list allows you to quickly identify any pods that might be experiencing issues.

1. Describing a Pod

If you find a pod that is not running as expected, use the kubectl describe pod command:

sh kubectl describe pod <pod-name>

This command provides detailed information about the pod and can often provide clues about what might be wrong.

Summary

In this tutorial, you learned how to debug issues with Kubernetes pods and containers. You learned how to access logs, how to access the shell within a container, and how to check the status and description of a pod.

For further learning, you may want to explore:

• How to use Kubernetes events for debugging
• How to set resource limits to prevent pods from consuming too much memory or CPU

Practice Exercises

1. Exercise 1: Diagnose a non-starting Pod. Use the kubectl describe pod command to identify the issue and fix it.

2. Exercise 2: Access the shell within a container of a running Pod. Use the ls command to list the files in the root directory.

3. Exercise 3: A pod is using too much CPU, causing other pods to be starved of resources. Identify the pod and limit its CPU usage.

Solutions and explanations:

1. Solution 1: The solution will largely depend on the specific issue. However, the kubectl describe pod command will give you detailed information about the pod's events and status, which can help you identify and resolve the problem.

2. Solution 2: Use the kubectl exec -it <pod-name> -- /bin/bash command to access the shell, then simply type ls and hit enter.

3. Solution 3: Use the kubectl top pod command to identify the pod's CPU usage. Then, edit the pod's configuration to limit its CPU usage. It can be done by adding a resources block in the pod's spec.

Keep practicing these exercises until you're comfortable with them. These are common tasks that you'll often perform when debugging pods and containers in Kubernetes.