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Free, open book · 38 chapters

Learn Kubernetes one chapter at a time

From your first pod to Helm, GitOps, operators and observability, with commands and manifests you run on your own cluster. Read it in order or jump to the chapter you need.

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New in this edition

Rewritten from scratch for Kubernetes 1.37, with every command checked against the official documentation.

Let's get startedReplica SetKubernetes ReplicaSet, hands-on: write the manifest, watch Pods self-heal, scale, adopt and orphan Pods, and learn when a Deployment is the better choice.Rewritten · Chapter 8Let's get startedNamespacesA hands-on Kubernetes namespace chapter: what it scopes and what it doesn't, creating and switching namespaces, cross-namespace DNS, quotas and stuck deletes.Rewritten · Chapter 10Let's get startedConfigMapsA hands-on Kubernetes ConfigMap chapter: create one from literals, files and env files, feed it to Pods as env vars or files, and roll out changes safely.Rewritten · Chapter 11Kubernetes Clusters Overview and UseK3s and K3supK3s step by step: what it bundles, the install script and its flags, kubeconfig from your laptop, joining agents with the token, k3sup over SSH, uninstall.Rewritten · Chapter 17Templating & IaCKustomizeKustomize with kubectl 1.37: build a base plus dev and prod overlays, set labels, images and replicas, generate ConfigMaps, patch, and pick Kustomize or Helm.Rewritten · Chapter 18Templating & IaCCrossplaneCrossplane v2 hands-on: install it with Helm, add a provider, create a managed resource, then build your own API with an XRD, a Composition and a function.Rewritten · Chapter 20Cloud Native Tools and Platformsk9sLearn k9s, the Kubernetes terminal UI: install it, drive a real deployment, port-forward and benchmark it, plus a full k9s commands and shortcuts reference.Rewritten · Chapter 24Cloud Native Tools and PlatformsGitOps and ArgoArgo CD tutorial for Argo CD 3.5: install it, log in with the initial admin secret, deploy an Application from Git, then turn on self-heal and prune.Rewritten · Chapter 26Advanced TopicsKubernetes OperatorsWhat a Kubernetes operator is, how CRDs and the reconcile loop fit together, a CloudNativePG install end to end, and building your own with Kubebuilder.Rewritten · Chapter 30Troubleshooting K8sCrashLoopBackOffCrashLoopBackOff explained: what the restart back-off means, the three kubectl commands that find the cause, exit codes, a fix for each cause, kubectl debug.Rewritten · Chapter 35Troubleshooting K8sImagePullBackOffImagePullBackOff in Kubernetes: read the pod events, confirm which of seven causes blocked the pull, from a tag typo to Docker Hub limits, and fix it.New chapter · Chapter 36Troubleshooting K8sOOMKilledOOMKilled in Kubernetes: what exit code 137 means, how to confirm it with kubectl, reproduce it on your own cluster, and size memory limits so it stops.New chapter · Chapter 37

Every chapter

13 parts, in the order a newcomer needs them.

01

Overview

  1. 1Introduction
  2. 2Contributors
02

Let's get started

  1. 3Introduction to Kubernetes
  2. 4Kubernetes Architecture
  3. 5Kubernetes Pods
  4. 6Setup Kubernetes Cluster
  5. 7Run Pods
  6. 8Replica Setupdated
  7. 9Kubernetes Deployment
  8. 10Namespacesupdated
  9. 11ConfigMapsupdated
03

Networking

  1. 12Kubernetes Service
  2. 13Kubernetes Ingress
  3. 14Service Mesh
04

Storage

  1. 15Kubernetes Volumes
05

Kubernetes Clusters Overview and Use

  1. 16KinD Cluster
  2. 17K3s and K3supupdated
06

Templating & IaC

  1. 18Kustomizeupdated
  2. 19Terraform
  3. 20Crossplaneupdated
07

Helm

  1. 21Helm Part 1
  2. 22Helm Part 2
  3. 23Helm Part 3
08

Cloud Native Tools and Platforms

  1. 24k9supdated
  2. 25Knative
  3. 26GitOps and Argoupdated
  4. 27Linkerd
09

Observability

  1. 28Prometheus
  2. 29Prometheus Exporter
10

Advanced Topics

  1. 30Kubernetes Operatorsupdated
11

Tutorials and Practice

  1. 31Serverless
  2. 32Ingress from scratch
  3. 33Istio from scratch
  4. 34Deploy to CIVO
12

Troubleshooting K8s

  1. 35CrashLoopBackOffupdated
  2. 36ImagePullBackOffupdated
  3. 37OOMKilledupdated
13

Glossary

  1. 38Terminology Primer

A free, open book for learning Kubernetes one topic at a time. It started as a public challenge: learn something new about Kubernetes every day for 100 days, and write down what you learned. The notes grew into the chapters below, in the order a newcomer needs them.

Each chapter explains one topic with commands and manifests you can run on your own cluster. Chapters marked as rewritten were written again from scratch in October 2026 for Kubernetes 1.37, with every command checked against the official documentation; the rest are the original notes, kept with their sources.

Where to start#

What the book covers#

Terms you meet along the way are collected in the Terminology Primer. To read the book from the first page, open the Introduction, or pick a chapter from the list above.