Kubernetes部署WordPress/MySQL时PersistentVolumeClaim报错求助

参考Kubernetes官方的WordPress/MySQL持久化应用示例部署，使用的配置文件如下：

Mysql-deployment.yaml #

apiVersion: v1
kind: Service
metadata:
  name: wordpress-mysql
  labels:
    app: wordpress
spec:
  ports:
    - port: 3306
  selector:
    app: wordpress
    tier: mysql
  clusterIP: None
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
  labels:
    app: wordpress
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: wordpress-mysql
  labels:
    app: wordpress
spec:
  selector:
    matchLabels:
      app: wordpress
      tier: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: wordpress
        tier: mysql
    spec:
      containers:
      - image: mysql:5.6
        name: mysql
        env:
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-pass
              key: password
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim

Worpress-deployment.yaml #

apiVersion: v1
kind: Service
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  ports:
    - port: 80
  selector:
    app: wordpress
    tier: frontend
  type: LoadBalancer
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: wp-pv-claim
  labels:
    app: wordpress
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  selector:
    matchLabels:
      app: wordpress
      tier: frontend
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: wordpress
        tier: frontend
    spec:
      containers:
      - image: wordpress:4.8-apache
        name: wordpress
        env:
        - name: WORDPRESS_DB_HOST
          value: wordpress-mysql
        - name: WORDPRESS_DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mysql-pass
              key: password
        ports:
        - containerPort: 80
          name: wordpress
        volumeMounts:
        - name: wordpress-persistent-storage
          mountPath: /var/www/html
      volumes:
      - name: wordpress-persistent-storage
        persistentVolumeClaim:
          claimName: wp-pv-claim

执行命令：

kubectl apply -k ./

得到输出：

service/wordpress created
service/wordpress-mysql created
persistentvolumeclaim/wp-pv-claim created
deployment.apps/wordpress created
deployment.apps/wordpress-mysql created
The PersistentVolumeClaim "mysql-pv-claim" is invalid: spec: Forbidden: spec is immutable after creation except resources.requests for bound claims
  core.PersistentVolumeClaimSpec{
        ... // 2 identical fields
        Resources:        {Requests: {s"storage": {i: {...}, s: "20Gi", Format: "BinarySI"}}},
        VolumeName:       "mysql-pv-volume",
-       StorageClassName: &"manual",
+       StorageClassName: nil,
        VolumeMode:       &"Filesystem",
        DataSource:       nil,
        DataSourceRef:    nil,
  }

Kubectl客户端/服务端版本为v1.25.9，请问该如何解决这个PersistentVolumeClaim无效的问题？

错误原因 #

mysql-pv-claim这个PVC已存在并绑定到了mysql-pv-volume这个PV上，此时你尝试修改PVC的spec.storageClassName字段（从"manual"改为空值），但Kubernetes规定：绑定后的PVC，除了存储请求量（resources.requests.storage）之外，其他spec字段均不可修改，因此触发了该禁止操作错误。

解决步骤 #

1. 删除已存在的PVC
   由于绑定后的PVC无法修改目标字段，只能先删除旧PVC：

   kubectl delete pvc mysql-pv-claim
   

   注意：如果对应PV的回收策略是Retain，删除PVC后PV会变为Released状态，需手动清理PV数据后才能重新绑定；如果是Delete策略，PV会随PVC一起删除，数据会丢失，请根据实际场景操作。

2. 重新执行部署
   再次运行部署命令，让Kubernetes根据当前配置重新创建PVC：

   kubectl apply -k ./
   

3. 可选：统一存储类配置（避免后续重复报错）
   若集群存在默认存储类，或希望指定固定存储类，可在两个PVC的spec中添加storageClassName字段，确保配置一致，示例如下：

   spec:
     accessModes:
       - ReadWriteOnce
     storageClassName: "manual" # 替换为你的集群实际存储类名称
     resources:
       requests:
         storage: 20Gi
   

   这样后续重新部署时，PVC的存储类配置不会变更，就不会触发类似错误。

内容的提问来源于stack exchange，提问作者eastwater