K3s Kubernetes Setup: Lightweight Container Orchestration

# Minimum requirements
# CPU: 1 core
# RAM: 512MB (recommended: 1GB+)
# Disk: 5GB
# OS: Ubuntu 20.04+, Debian 11+, CentOS 8+

# System update
apt update && apt upgrade -y

# Install required tools
apt install -y curl wget

# Install K3s (server mode)
curl -sfL https://get.k3s.io | sh -

# Check service status after installation
systemctl status k3s

# Check cluster status
kubectl get nodes

# List all pods
kubectl get pods -A

# Copy kubeconfig for kubectl
mkdir -p ~/.kube
cp /etc/rancher/k3s/k3s.yaml ~/.kube/config
chmod 600 ~/.kube/config

# Set KUBECONFIG environment variable
export KUBECONFIG=~/.kube/config
echo 'export KUBECONFIG=~/.kube/config' >> ~/.bashrc

# View cluster info
kubectl cluster-info

# Install master node and save token
curl -sfL https://get.k3s.io | sh -

# Get node token (required for worker nodes)
cat /var/lib/rancher/k3s/server/node-token
# Output: K10xxx...::server:yyy...

# Join worker node to master
curl -sfL https://get.k3s.io | K3S_URL=https://MASTER_IP:6443 K3S_TOKEN=NODE_TOKEN sh -

# Verify worker joined on master
kubectl get nodes
# NAME          STATUS   ROLES                  AGE
# master-node   Ready    control-plane,master   10m
# worker-node1  Ready    <none>                 2m

# List nodes
kubectl get nodes
kubectl get nodes -o wide  # Detailed info

# List pods
kubectl get pods
kubectl get pods -n kube-system  # System pods
kubectl get pods -A              # All namespaces

# List deployments
kubectl get deployments

# List services
kubectl get services

# List namespaces
kubectl get namespaces

# View resource details
kubectl describe pod POD_NAME
kubectl describe node NODE_NAME

# View pod logs
kubectl logs POD_NAME
kubectl logs -f POD_NAME  # Live logs

# Run command in pod
kubectl exec -it POD_NAME -- /bin/bash

# nginx-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.25
        ports:
        - containerPort: 80
        resources:
          requests:
            memory: "64Mi"
            cpu: "250m"
          limits:
            memory: "128Mi"
            cpu: "500m"

# Apply deployment
kubectl apply -f nginx-deployment.yaml

# Check deployment status
kubectl get deployments
kubectl rollout status deployment/nginx-deployment

# List pods
kubectl get pods -l app=nginx

# nginx-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
      nodePort: 30080
  type: NodePort

# Apply service
kubectl apply -f nginx-service.yaml

# Check service
kubectl get services

# Access via browser: http://SERVER_IP:30080

# Create namespaces
kubectl create namespace production
kubectl create namespace staging

# Deploy to namespace
kubectl apply -f deployment.yaml -n production

# List resources in namespace
kubectl get all -n production

# Change default namespace
kubectl config set-context --current --namespace=production

# Install Helm
curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash

# Check Helm version
helm version

# Add Bitnami repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

# Install WordPress
helm install my-wordpress bitnami/wordpress \
  --set wordpressUsername=admin \
  --set wordpressPassword=StrongPass123! \
  --set service.type=NodePort

# List installed charts
helm list

# Remove chart
helm uninstall my-wordpress

# pvc.yaml — Persistent Volume Claim
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: app-data
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: local-path  # K3s default storage class
  resources:
    requests:
      storage: 5Gi

# Create PVC
kubectl apply -f pvc.yaml

# Check PVC status
kubectl get pvc

# List storage classes
kubectl get storageclass

# Create ConfigMap
kubectl create configmap app-config \
  --from-literal=DB_HOST=localhost \
  --from-literal=APP_ENV=production

# Create Secret
kubectl create secret generic app-secret \
  --from-literal=DB_PASSWORD=StrongPass123! \
  --from-literal=API_KEY=abc123

# View ConfigMap
kubectl get configmap app-config -o yaml

# View Secret (base64 encoded)
kubectl get secret app-secret -o yaml

# Update K3s
curl -sfL https://get.k3s.io | INSTALL_K3S_VERSION=v1.28.0+k3s1 sh -

# Manage K3s service
systemctl stop k3s
systemctl start k3s
systemctl restart k3s

# View K3s logs
journalctl -u k3s -f

# Uninstall K3s
/usr/local/bin/k3s-uninstall.sh

# Remove worker node
/usr/local/bin/k3s-agent-uninstall.sh

# Install Kubernetes Dashboard
kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.7.0/aio/deploy/recommended.yaml

# Create admin user
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ServiceAccount
metadata:
  name: admin-user
  namespace: kubernetes-dashboard
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: admin-user
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- kind: ServiceAccount
  name: admin-user
  namespace: kubernetes-dashboard
EOF

# Generate token
kubectl -n kubernetes-dashboard create token admin-user

# Start proxy for dashboard access
kubectl proxy
# http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/