Kubernetes Core Concepts - Learn Step by Step

📋 What is Kubernetes?

🎯 Why Kubernetes Matters

The Problem: Managing containers at scale is complex. You need to handle deployment, scaling, networking, and failures.

The Solution: Kubernetes automates container orchestration, making it easy to deploy and manage containerized applications.

Real Impact: Companies like Google run billions of containers per week using Kubernetes!

🏢

Real-World Analogy

Think of Kubernetes as a shipping port manager:

📦 Containers = Shipping containers with your goods (applications)
🚢 Pods = Ships that carry containers
🏗️ Nodes = Docks where ships can park
👨‍✈️ Control Plane = Port authority managing everything
📋 Scheduler = Decides which ship goes to which dock

Core Benefits of Kubernetes

🔄

Auto-Scaling

🛡️

Self-Healing

🚀

Automated Rollouts

⚖️

Load Balancing

⚙️ Control Plane Components

Component	Purpose	Key Functions
kube-apiserver	API endpoint for Kubernetes	• Validates and processes REST requests • Updates etcd • Only component that talks to etcd
etcd	Distributed key-value store	• Stores all cluster data • Provides high availability • Source of truth for cluster state
kube-scheduler	Assigns pods to nodes	• Watches for new pods • Selects best node • Considers resource requirements
kube-controller-manager	Runs controller processes	• Node controller • Replication controller • Endpoints controller
cloud-controller-manager	Cloud-specific control logic	• Node controller • Route controller • Service controller

Node Components

💡 Key Node Components

kubelet: Agent that runs on each node, ensures containers are running in pods
kube-proxy: Network proxy that maintains network rules for pod communication
Container Runtime: Software for running containers (Docker, containerd, CRI-O)

Check Cluster Components

# View all components in kube-system namespace
kubectl get pods -n kube-system

# Check component status
kubectl get componentstatuses

# View nodes in cluster
kubectl get nodes -o wide

# Describe a specific node
kubectl describe node <node-name>

💻 Hands-On: Exploring Your Cluster

🚀 Let's Explore a Real Cluster!

Follow these steps to understand your Kubernetes cluster structure:

Step 1: Basic Cluster Information

cluster-info.sh

# Get cluster information
kubectl cluster-info

# View kubectl configuration
kubectl config view

# Get current context
kubectl config current-context

# List all contexts
kubectl config get-contexts

Step 2: Create Your First Namespace

namespace.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: my-first-namespace
  labels:
    environment: learning
    created-by: tutorial

Apply and Verify

# Create the namespace
kubectl apply -f namespace.yaml

# List all namespaces
kubectl get namespaces

# Describe the namespace
kubectl describe namespace my-first-namespace

Step 3: Understanding API Resources

Explore API Resources

# List all available API resources
kubectl api-resources

# Get API versions
kubectl api-versions

# Explain a resource
kubectl explain pods
kubectl explain pods.spec.containers

⚠️ Common Pitfall

Problem: "The connection to the server localhost:8080 was refused"

Solution: This means kubectl can't connect to your cluster. Check:

Is your cluster running? (minikube status, kind get clusters)
Is KUBECONFIG environment variable set correctly?
Run: kubectl config view to check configuration

🎯 Practice Exercises

Exercise 1: Cluster Exploration

Objective: Familiarize yourself with cluster components

List all nodes in your cluster
Check which pods are running in kube-system namespace
Find out which version of Kubernetes you're running
Identify the container runtime on your nodes

💡 Solution

# 1. List nodes
kubectl get nodes

# 2. Pods in kube-system
kubectl get pods -n kube-system

# 3. Kubernetes version
kubectl version --short

# 4. Container runtime
kubectl get nodes -o wide

Exercise 2: Working with Namespaces

Objective: Create and manage namespaces

Create a namespace called "development"
Create another namespace called "production"
Add labels to identify environments
Set resource quotas for the development namespace

💡 Solution

# Create namespaces
kubectl create namespace development
kubectl create namespace production

# Add labels
kubectl label namespace development env=dev
kubectl label namespace production env=prod

# Create resource quota
cat <



                    
                        Exercise 3: API Server Interaction
                        Objective: Understand how kubectl communicates with the API server
                        
                            Use kubectl with increased verbosity to see API calls
                            Get raw JSON output for a namespace
                            Use kubectl proxy to access the API directly
                        
                        
                        
                            💡 Solution
                            
                                # 1. Verbose output
kubectl get nodes -v=8

# 2. Raw JSON
kubectl get namespace default -o json

# 3. Start proxy
kubectl proxy --port=8001 &
# Access API
curl http://localhost:8001/api/v1/namespaces



                
                
                    📖 Quick Reference

                    Essential kubectl Commands
                    
                        
                            
                                
                                    Command
                                    Description
                                    Example
                                
                            
                            
                                
                                    kubectl get
                                    List resources
                                    kubectl get nodes
                                
                                
                                    kubectl describe
                                    Show detailed information
                                    kubectl describe node node-1
                                
                                
                                    kubectl create
                                    Create a resource
                                    kubectl create namespace test
                                
                                
                                    kubectl apply
                                    Apply configuration
                                    kubectl apply -f config.yaml
                                
                                
                                    kubectl delete
                                    Delete resources
                                    kubectl delete namespace test
                                
                                
                                    kubectl logs
                                    View container logs
                                    kubectl logs pod-name
                                
                                
                                    kubectl exec
                                    Execute command in container
                                    kubectl exec -it pod-name -- bash
                                
                            
                        
                    

                    Kubernetes Object Model
                    
                        📝 Key Concepts
                        
                            API Version: The version of the Kubernetes API you're using (e.g., v1, apps/v1)
                            Kind: The type of object you want to create (e.g., Pod, Service, Deployment)
                            Metadata: Data that helps uniquely identify the object (name, labels, namespace)
                            Spec: The desired state of the object
                            Status: The current state of the object (managed by Kubernetes)
                        
                    

                    Useful Resources
                    
                        📚 Learning Resources
                        
                            🔗 Official Kubernetes Documentation
                            🔗 Kubernetes The Hard Way
                            🔗 kubectl Cheat Sheet
                            🔗 Troubleshooting Guide
                        
                    
                

                
                
                    
                        ← Back to Overview
                    
                    
                        Next: Pods & Containers →

Command	Description	Example
`kubectl get`	List resources	`kubectl get nodes`
`kubectl describe`	Show detailed information	`kubectl describe node node-1`
`kubectl create`	Create a resource	`kubectl create namespace test`
`kubectl apply`	Apply configuration	`kubectl apply -f config.yaml`
`kubectl delete`	Delete resources	`kubectl delete namespace test`
`kubectl logs`	View container logs	`kubectl logs pod-name`
`kubectl exec`	Execute command in container	`kubectl exec -it pod-name -- bash`

🚢 Kubernetes Core Concepts & Architecture

📋 What is Kubernetes?

🎯 Why Kubernetes Matters

Real-World Analogy

Core Benefits of Kubernetes

🏗️ Kubernetes Architecture

Architecture Components Explained

Control Plane (Master)

Worker Nodes

Pods

⚙️ Control Plane Components

Node Components

💡 Key Node Components

💻 Hands-On: Exploring Your Cluster

🚀 Let's Explore a Real Cluster!

Step 1: Basic Cluster Information

Step 2: Create Your First Namespace

Step 3: Understanding API Resources

⚠️ Common Pitfall

🎯 Practice Exercises

Exercise 1: Cluster Exploration

Exercise 2: Working with Namespaces

Exercise 3: API Server Interaction

📖 Quick Reference

Essential kubectl Commands

Kubernetes Object Model

📝 Key Concepts

Useful Resources

📚 Learning Resources