Kubernetes Concepts: Simplified

This repository explains Kubernetes concepts in a really simple way. It contains configuration files (.yml), commands, and explanations to help you learn by doing.

##🛠 PrerequisitesBefore running the commands, ensure you have the following installed:

1. Docker (The engine to run containers)
2. Kind (Kubernetes in Docker - creates local clusters)
3. Kubectl (The CLI tool to talk to the cluster)

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##🚀 1. Cluster Management (Kind)These commands are used to create, manage, and destroy your local Kubernetes cluster.

###Create a Basic ClusterCreates a default cluster named local.

kind create cluster --name local

###Verify the ClusterCheck if the Docker container acting as the "node" is running.

docker ps

Create a Cluster with ConfigUse the provided clusters.yml to create a multi-node cluster or custom configuration.

kind create cluster --config clusters.yml --name local

###Switch Context (If needed)If you have multiple clusters, ensure kubectl is talking to the right one.

kubectl cluster-info --context kind-local

###Delete the ClusterTear down the cluster and clean up resources.

kind delete cluster --name local

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2. Working with Resources (Kubectl)The primary command to create or update any resource (Pod, Deployment, Service, etc.) from a file is apply.

# General syntax
kubectl apply -f <filename>.yml

PodsThe smallest deployable unit in Kubernetes.

# Create a pod from file
kubectl apply -f pod.yml

# List all running pods
kubectl get pods

# List pods with more details (IP address, Node)
kubectl get pods -o wide

# View logs of a specific pod
kubectl logs <pod-name>

# Get inside the container (interactive shell)
kubectl exec -it <pod-name> -- /bin/bash

ReplicaSetsEnsures a specified number of pod replicas are running.

# Create replicaset
kubectl apply -f replicaset.yml

# Check the status of replicas
kubectl get replicaset

# View details (events, current replicas)
kubectl describe replicaset <replicaset-name>

DeploymentsManages ReplicaSets and provides declarative updates (rollouts/rollbacks).

# Create deployment
kubectl apply -f deployment.yml

# Watch the deployment roll out in real-time
kubectl rollout status deployment/<deployment-name>

# Update the image used in a deployment
kubectl set image deployment/<deployment-name> <container-name>=<new-image>:tag

# Undo a deployment (Rollback)
kubectl rollout undo deployment/<deployment-name>

ServicesExposes your application to the network.

# Create service
kubectl apply -f services.yml

# List services
kubectl get svc

# Access a service running in Kind from your local machine (Port Forwarding)
# Syntax: kubectl port-forward service/<service-name> <local-port>:<service-port>
kubectl port-forward service/my-service 8080:80

Complete Example (complete.yml)A comprehensive manifest that demonstrates a real-world setup with multiple resources working together.

This manifest includes:

• Two Deployments: nginx-deployment and apache-deployment (each with 2 replicas)
• Two Services: nginx-service and apache-service (ClusterIP type)
• One Ingress: web-apps-ingress for routing external traffic to both services

# Deploy the complete example
kubectl apply -f complete.yml

# Check all resources created
kubectl get all
kubectl get ingress

# View the ingress details
kubectl describe ingress web-apps-ingress

# To use the Ingress, you'll need an Ingress Controller installed
# For Kind clusters, you can install the NGINX Ingress Controller:
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/main/deploy/static/provider/kind/deploy.yaml

# After the controller is ready, you can access:
# - nginx service at: http://your-domain.com/nginx
# - apache service at: http://your-domain.com/apache
# (Update /etc/hosts to map your-domain.com to localhost if testing locally)

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3. Debugging & InspectionWhen things go wrong, use these commands to investigate.

# Get everything in the current namespace
kubectl get all

# Describe: The most useful command for debugging errors
# (Shows events, errors, and configuration details)
kubectl describe pod <pod-name>
kubectl describe service <service-name>

# Delete a specific resource
kubectl delete -f <filename>.yml

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Pro Tip: AliasesTo save time, many developers alias kubectl to k.

alias k=kubectl
# Example: k get pods