参考：
https://kubernetes.io/zh/docs/concepts/storage/storage-classes/
https://kubernetes.io/docs/tasks/run-application/run-replicated-stateful-application/
https://github.com/kubernetes-retired/external-storage/tree/master/nfs
https://www.jianshu.com/p/65ed4bdf0e89
https://www.cnblogs.com/panwenbin-logs/p/12196286.html

遇到的错误

1，3 pod has unbound immediate PersistentVolumeClaims.

根据官网安装mysql,需要PersistentVolumeClaim，不然会报3 pod has unbound immediate PersistentVolumeClaims:

2，mysql Back-off restarting failed container

这个原因有很多，比如k8s gcr.io被墙导致ImagePullBackOff，或者节点内存不足导致caused "process_linux.go:101: executing setns process caused "exit status 1， 等。

如果k8s gcr.io被墙导致ImagePullBackOff，可以通过以下命令拉去镜像。

docker pull ist0ne/xtrabackup
docker tag ist0ne/xtrabackup:latest gcr.io/google-samples/xtrabackup:1.0

注意如果是云集群，那个每个节点都要执行以上命令拉去镜像。

3，chown: changing ownership of ‘/var/lib/mysql/’: Operation not permitted

这个是由nfs的权限设置导致的。具体解决办法见NFS安装步骤–主节点执行。

安装步骤

• 一、环境准备–NFS

我的k8s有三个节点，一个master，两个node分别是以下三个。
192.168.0.11  k8s-master
192.168.0.22  k8s-node1
192.168.0.33  k8s-node2

1，主节点执行

yum -y install nfs-utils rpcbind
mkdir -p /home/nfs
vi /etc/exports
#加入,注意加入no_root_squash，这个是放开root权限，不加的话会报chown: changing ownership of '/var/lib/mysql/': Operation not permitted错误。
/home/nfs *(insecure,rw,async,no_root_squash)

#启动并设置开机启动
systemctl start rpcbind.service
systemctl status rpcbind.service
systemctl enable rpcbind.service

systemctl start nfs.service
systemctl enable nfs.service
systemctl status nfs.service

2，node节点验证nfs可用

yum -y intall nfs-utils 
showmount -e 192.1681.0.11
# 挂载至本地/mnt目录
mount -t nfs 192.1681.0.11:/home/nfs /mnt 
df -h
umount /mnt

• 二、配置PersistentVolumeClaims

1,配置account并配置相关权限（rabc.yaml）,并使用 kubectl apply -f rabc.yaml执行，该文件主要设置nfs相关角色、权限信息。

# rabc.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: nfs-client-provisioner
  # replace with namespace where provisioner is deployed
  namespace: default        #根据实际环境设定namespace,下面类同
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: nfs-client-provisioner-runner
rules:
  - apiGroups: [""]
    resources: ["persistentvolumes"]
    verbs: ["get", "list", "watch", "create", "delete"]
  - apiGroups: [""]
    resources: ["persistentvolumeclaims"]
    verbs: ["get", "list", "watch", "update"]
  - apiGroups: ["storage.k8s.io"]
    resources: ["storageclasses"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create", "update", "patch"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: run-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    # replace with namespace where provisioner is deployed
    namespace: default
roleRef:
  kind: ClusterRole
  name: nfs-client-provisioner-runner
  apiGroup: rbac.authorization.k8s.io
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
    # replace with namespace where provisioner is deployed
  namespace: default
rules:
  - apiGroups: [""]
    resources: ["endpoints"]
    verbs: ["get", "list", "watch", "create", "update", "patch"]
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    # replace with namespace where provisioner is deployed
    namespace: default
roleRef:
  kind: Role
  name: leader-locking-nfs-client-provisioner
  apiGroup: rbac.authorization.k8s.io

2，创建StorageClass，并使用 kubectl apply -f storage-class.yaml执行，

# storage-class.yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name:  managed-nfs-storag
provisioner: nfs  #这里的名称要和provisioner配置文件中的环境变量PROVISIONER_NAME保持一致
parameters:
  type: gp2
reclaimPolicy: Retain
allowVolumeExpansion: true
mountOptions:
  - debug
volumeBindingMode: Immediate

3，创建provisioner,并使用 kubectl apply -f nfs-provisioner.yaml执行

# nfs-provisioner.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nfs-client-provisioner
  labels:
    app: nfs-client-provisioner
  # replace with namespace where provisioner is deployed
  namespace: default  #与RBAC文件中的namespace保持一致
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nfs-client-provisioner
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: nfs-client-provisioner
  template:
    metadata:
      labels:
        app: nfs-client-provisioner
    spec:
      serviceAccountName: nfs-client-provisioner
      containers:
        - name: nfs-client-provisioner
          image: quay.io/external_storage/nfs-client-provisioner:latest
          volumeMounts:
            - name: nfs-client-root
              mountPath: /persistentvolumes
          env:
            - name: PROVISIONER_NAME
              value: nfs  #provisioner名称,请确保该名称与 nfs-StorageClass.yaml文件中的provisioner名称保持一致
            - name: NFS_SERVER
              value: 192.168.0.11   #NFS Server IP地址
            - name: NFS_PATH  
              value: /home/nfs    #NFS挂载卷
      volumes:
        - name: nfs-client-root
          nfs:
            server: 192.168.0.11  #NFS Server IP地址
            path: /home/nfs     #NFS 挂载卷

4，创建PersistentVolumeClaim，,并使用 kubectl apply -f nfs-pvc.yaml执行

# pvc-nfs.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data
spec:
  accessModes:
    - ReadWriteOnce
  volumeMode: Filesystem
  resources:
    requests:
      storage: 8Gi
  storageClassName:  managed-nfs-storag

• 三、创建mysql集群

1，创建mysql-configmap，该文件主要是mysql的配置信息，这里设置mysql主节点与子节点的读写策略。

# mysql-configmap.yaml
kind: ConfigMap
apiVersion: v1
metadata:
  name: mysql
  namespace: default
  labels:
    app: mysql
data:
  master.cnf: |
    # Apply this config only on the master.
    [mysqld]
    log-bin
  slave.cnf: |
    # Apply this config only on slaves.
    [mysqld]
    super-read-only

2，创建mysql-services.yaml

apiVersion: v1
kind: Service
metadata:
  name: mysql
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  clusterIP: None
  selector:
    app: mysql
---
apiVersion: v1
kind: Service
metadata:
  name: mysql-read
  labels: 
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  selector:
    app: mysql

3,创建mysql-statefulset.yaml

kind: StatefulSet
apiVersion: apps/v1
metadata:
  name: mysql
  namespace: default
spec:
  replicas: 3
  selector:
    matchLabels:
      app: mysql
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: mysql
    spec:
      volumes:
        - name: conf
          emptyDir: {}
        - name: config-map
          configMap:
            name: mysql
            defaultMode: 420
      initContainers:
        - name: init-mysql
          image: 'mysql:5.7'
          command:
            - bash
            - '-c'
            - |
              set -ex
              # Generate mysql server-id from pod ordinal index.
              [[ `hostname` =~ -([0-9]+)$ ]] || exit 1
              ordinal=${BASH_REMATCH[1]}
              echo [mysqld] > /mnt/conf.d/server-id.cnf
              # Add an offset to avoid reserved server-id=0 value.
              echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf
              # Copy appropriate conf.d files from config-map to emptyDir.
              if [[ $ordinal -eq 0 ]]; then
                cp /mnt/config-map/master.cnf /mnt/conf.d/
              else
                cp /mnt/config-map/slave.cnf /mnt/conf.d/
              fi
          resources: {}
          volumeMounts:
            - name: conf
              mountPath: /mnt/conf.d
            - name: config-map
              mountPath: /mnt/config-map
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
          imagePullPolicy: IfNotPresent
        - name: clone-mysql
          image: 'gcr.io/google-samples/xtrabackup:1.0'
          command:
            - bash
            - '-c'
            - >
              set -ex

              # Skip the clone if data already exists.

              [[ -d /var/lib/mysql/mysql ]] && exit 0

              # Skip the clone on master (ordinal index 0).

              [[ `hostname` =~ -([0-9]+)$ ]] || exit 1

              ordinal=${BASH_REMATCH[1]}

              [[ $ordinal -eq 0 ]] && exit 0

              # Clone data from previous peer.

              ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C
              /var/lib/mysql

              # Prepare the backup.

              xtrabackup --prepare --target-dir=/var/lib/mysql
          resources: {}
          volumeMounts:
            - name: nfs-pvc
              mountPath: /var/lib/mysql
              subPath: mysql
            - name: conf
              mountPath: /etc/mysql/conf.d
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
          imagePullPolicy: IfNotPresent
      containers:
        - name: mysql
          image: 'mysql:5.7'
          ports:
            - name: mysql
              containerPort: 3306
              protocol: TCP
          env:
            - name: MYSQL_ALLOW_EMPTY_PASSWORD
              value: '1'
          resources:
            requests:
              cpu: 50m
              memory: 50Mi
          volumeMounts:
            - name: nfs-pvc
              mountPath: /var/lib/mysql
              subPath: mysql
            - name: conf
              mountPath: /etc/mysql/conf.d
          livenessProbe:
            exec:
              command:
                - mysqladmin
                - ping
            initialDelaySeconds: 30
            timeoutSeconds: 5
            periodSeconds: 10
            successThreshold: 1
            failureThreshold: 3
          readinessProbe:
            exec:
              command:
                - mysql
                - '-h'
                - 127.0.0.1
                - '-e'
                - SELECT 1
            initialDelaySeconds: 5
            timeoutSeconds: 1
            periodSeconds: 2
            successThreshold: 1
            failureThreshold: 3
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
          imagePullPolicy: IfNotPresent
        - name: xtrabackup
          image: 'gcr.io/google-samples/xtrabackup:1.0'
          command:
            - bash
            - '-c'
            - >
              set -ex

              cd /var/lib/mysql


              # Determine binlog position of cloned data, if any.

              if [[ -f xtrabackup_slave_info && "x$(<xtrabackup_slave_info)" !=
              "x" ]]; then
                # XtraBackup already generated a partial "CHANGE MASTER TO" query
                # because we're cloning from an existing slave. (Need to remove the tailing semicolon!)
                cat xtrabackup_slave_info | sed -E 's/;$//g' > change_master_to.sql.in
                # Ignore xtrabackup_binlog_info in this case (it's useless).
                rm -f xtrabackup_slave_info xtrabackup_binlog_info
              elif [[ -f xtrabackup_binlog_info ]]; then
                # We're cloning directly from master. Parse binlog position.
                [[ `cat xtrabackup_binlog_info` =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1
                rm -f xtrabackup_binlog_info xtrabackup_slave_info
                echo "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\
                      MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.in
              fi


              # Check if we need to complete a clone by starting replication.

              if [[ -f change_master_to.sql.in ]]; then
                echo "Waiting for mysqld to be ready (accepting connections)"
                until mysql -h 127.0.0.1 -e "SELECT 1"; do sleep 1; done

                echo "Initializing replication from clone position"
                mysql -h 127.0.0.1 \
                      -e "$(<change_master_to.sql.in), \
                              MASTER_HOST='mysql-0.mysql', \
                              MASTER_USER='root', \
                              MASTER_PASSWORD='', \
                              MASTER_CONNECT_RETRY=10; \
                            START SLAVE;" || exit 1
                # In case of container restart, attempt this at-most-once.
                mv change_master_to.sql.in change_master_to.sql.orig
              fi


              # Start a server to send backups when requested by peers.

              exec ncat --listen --keep-open --send-only --max-conns=1 3307 -c \
                "xtrabackup --backup --slave-info --stream=xbstream --host=127.0.0.1 --user=root"
              tail -f /dev/null
          ports:
            - name: xtrabackup
              containerPort: 3307
              protocol: TCP
          resources:
            requests:
              cpu: 50m
              memory: 50Mi
          volumeMounts:
            - name: nfs-pvc
              mountPath: /var/lib/mysql
              subPath: mysql
            - name: conf
              mountPath: /etc/mysql/conf.d
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
          imagePullPolicy: IfNotPresent
      restartPolicy: Always
      terminationGracePeriodSeconds: 30
      dnsPolicy: ClusterFirst
      securityContext: {}
      schedulerName: default-scheduler
  volumeClaimTemplates:
    - kind: PersistentVolumeClaim
      apiVersion: v1
      metadata:
        name: nfs-pvc
        creationTimestamp: null
      spec:
        accessModes:
          - ReadWriteMany
        resources:
          requests:
            storage: 1Mi
        storageClassName: managed-nfs-storage
        volumeMode: Filesystem
      status:
        phase: Pending