Kubernetes (k8s) is an open-source system for automating deployment, scaling, and management of containerized applicasions. The core components include:

• Master Node:
  • kube-apiserver: API entry point for cluster operations
  • etcd: Distributed key-value store for cluster data
  • kube-scheduler: Assigns pods to nodes
  • Controller Manager: Manages replication, node health, etc.
• Worker Node:
  • kubelet: Node agent for container management
  • kube-proxy: Network proxy for service discovery
  • Container Runtime: Docker, containerd, etc.

Core Concepts

Cluster Installation Steps

1. Prerequisites:
   • Minimum 2GB RAM, 2 CPUs
   • Disable swap
   • Install Docker
2. Initialize Master Node: ``` kubeadm init
   --apiserver-advertise-address=10.0.2.15
   --image-repository registry.aliyuncs.com/google_containers
   --kubernetes-version v1.17.3
   --service-cidr=10.96.0.0/16
   --pod-network-cidr=10.244.0.0/16

3. Join Worker Nodes: ``` kubeadm join 10.0.2.15:6443
   --token abcdef.0123456789abcdef
   --discovery-token-ca-cert-hash sha256:1234567890abcdef

4. Install CNI Plugin: ``` kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

KubeSphere Installation

1. Install Helm: ``` curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bash

2. Configure Tiller: ``` kubectl create serviceaccount tiller -n kube-system kubectl create clusterrolebinding tiller --clusterrole=cluster-admin --serviceaccount=kube-system:tiller

3. Deploy KubeSphere: ``` kubectl apply -f https://github.com/kubesphere/ks-installer/releases/download/v3.1.1/kubesphere-installer.yaml kubectl apply -f https://github.com/kubesphere/ks-installer/releases/download/v3.1.1/cluster-configuration.yaml

4. Monitor Installation: ``` kubectl logs -n kubesphere-system $(kubectl get pod -n kubesphere-system -l app=ks-install -o jsonpath='{.items[0].metadata.name}') -f

YAML Configuraton Examples

Deployment Example

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:latest
        ports:
        - containerPort: 8080

Service Example

apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  type: NodePort
  ports:
  - port: 80
    targetPort: 8080
    nodePort: 30001
  selector:
    app: myapp

Ingress Example

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
spec:
  rules:
  - http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              number: 80
  ingressClassName: nginx