Kubernetes（K8s）完全指南：集群搭建与核心概念

Kubernetes 简介

Kubernetes（简称 K8s）是一个开源的容器编排平台，用于自动化容器化应用的部署、扩展和管理。本文详细介绍 K8s 的核心概念和实战用法。

为什么需要 Kubernetes？

• 容器编排 - 管理数千个容器
• 自动修复 - 故障自动重启
• 水平扩展 - 根据负载自动扩缩容
• 服务发现 - 内部服务自动寻址
• 滚动更新 - 零停机部署

Kubernetes 核心概念

1. Pod

Pod 是 K8s 的最小调度单元，一个 Pod 可以包含一个或多个容器。

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp
    image: nginx:1.21
    ports:
    - containerPort: 80
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"
      requests:
        memory: "64Mi"
        cpu: "250m"

2. Deployment

Deployment 管理 Pod 的部署，提供声明式的更新机制。

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:1.0
        ports:
        - containerPort: 8080
        env:
        - name: NODE_ENV
          value: "production"
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 10
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 15
          periodSeconds: 20

3. Service

Service 为 Pod 提供稳定的访问入口。

# ClusterIP - 集群内部访问
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 8080
  type: ClusterIP

---
# NodePort - 外部访问
apiVersion: v1
kind: Service
metadata:
  name: myapp-nodeport
spec:
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 8080
    nodePort: 30080
  type: NodePort

---
# LoadBalancer - 云厂商负载均衡
apiVersion: v1
kind: Service
metadata:
  name: myapp-lb
spec:
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 8080
  type: LoadBalancer

4. Ingress

Ingress 提供 HTTP/HTTPS 路由。

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              number: 80

5. ConfigMap 和 Secret

管理配置和敏感数据。

# ConfigMap
apiVersion: v1
kind: ConfigMap
metadata:
  name: myapp-config
data:
  database_url: "postgres://db:5432/myapp"
  config.yaml: |
    server:
      port: 8080
    log:
      level: info

---
# Secret
apiVersion: v1
kind: Secret
metadata:
  name: myapp-secret
type: Opaque
data:
  # base64 编码
  username: YWRtaW4=
  password: cGFzc3dvcmQ=

6. PersistentVolume (PV) 和 PersistentVolumeClaim (PVC)

持久化存储。

# PersistentVolume
apiVersion: v1
kind: PersistentVolume
metadata:
  name: my-pv
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: /data/myapp

---
# PersistentVolumeClaim
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

常用命令

# 查看资源
kubectl get pods
kubectl get services
kubectl get deployments
kubectl get all

# 查看详情
kubectl describe pod myapp-pod
kubectl get pod myapp -o yaml

# 日志
kubectl logs -f myapp-pod
kubectl logs -f myapp-pod -c container-name

# 进入容器
kubectl exec -it myapp-pod -- /bin/bash

# 扩缩容
kubectl scale deployment myapp --replicas=5

# 更新镜像
kubectl set image deployment/myapp myapp=myapp:2.0

# 回滚
kubectl rollout undo deployment/myapp
kubectl rollout status deployment/myapp

Minikube 本地搭建

# 安装 Minikube
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64
sudo install minikube-linux-amd64 /usr/local/bin/minikube

# 安装 kubectl
curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
sudo install kubectl /usr/local/bin/

# 启动集群
minikube start --driver=docker
# 或使用 VirtualBox
minikube start --driver=virtualbox

# 启用插件
minikube addons enable ingress
minikube addons enable dashboard

# 打开 Dashboard
minikube dashboard

总结

Kubernetes 是云原生时代的操作系统，掌握其核心概念和常用命令是每个 DevOps 工程师的必备技能。本文涵盖了 K8s 的核心资源类型和基本用法，希望对你学习 K8s 有所帮助。

参考资源：Kubernetes 官方文档

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