本文探讨在 Host 上创建并导出共享NFS挂载，并将它（NFS）作为K8s集群中的持久卷存储。

在深入这些步骤之前，先了解一下共享NFS。

1.创建NFS server并提供共享存储，在网络上其他主机可以使用分享的存储。

[root@nfs ~]# exportfs -v
/data           <world>(sync,wdelay,hide,no_subtree_check,sec=sys,rw,secure,no_root_squash,no_all_squash)

2.K8s集群中节点（Ubuntu操作系统）上安装nfs-common

sudo apt install nfs-common

3.使用host主机的NFS共享创建 PersistentVolume和PersistentVolumeClaim

PersistentVolume

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-volume
spec:
  capacity:
    storage: 256Mi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: standard
  mountOptions:
    - hard
    - nfsvers=4.1
  nfs:
    path: /data
    server: 192.168.2.27

PersistentVolumeClaim

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-claim
spec:
  resources:
    requests:
      storage: 128Mi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce

我们可以使用 kubernetes get pv,pvc 命令查看已创建的 PersistentVolume 和 PersistentVolumeClaim

4.创建一个Deployment

yaml 文件创建部署信息如下：

调度 2 个 busybox pod
卷挂载到 /my-test
并将 pod 的 “当前时间 ”和 “主机名 ”写入 /my-test/shared.txt 文件。

apiVersion: apps/v1
kind: Deployment
metadata:
  name: standard-host-path-nfs-pvc-deployment
  namespace: default
  labels:
    app: standard-host-path-nfs-pvc-deployment
spec:
  selector:
    matchLabels:
      app: mypod
  replicas: 2
  template:
    metadata:
      labels:
        app: mypod
    spec:
      containers:
        - name: pause
          image: busybox
          imagePullPolicy: IfNotPresent
          command:
          - /bin/sh
          - -c
          - 'sleep 60; for i in  $(seq 1 5); do host=$(hostname); now=$(date +"%T"); echo "adding time: $now, from $host" >> /my-test/shared.txt; sleep 10; done; sleep infinity'
          ports:
          - containerPort: 80
          volumeMounts:
          - name: vola
            mountPath: /my-test
      volumes:
      - name: vola
        persistentVolumeClaim:
          claimName: nfs-claim

执行以下命令创建部署

andy@hostease:~/vsproject/nfs$ kubectl apply -f standard-host-path-nfs-pvc-deployment.yaml 
deployment.apps/standard-host-path-nfs-pvc-deployment created

获取Pod

andy@hostease:~/vsproject/nfs$ kubectl get pods -o wide
NAME                                                     READY   STATUS    RESTARTS   AGE     IP            NODE       NOMINATED NODE   READINESS GATES
standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9   1/1     Running   0          5m11s   10.244.0.17   minikube   <none>           <none>
standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh   1/1     Running   0          5m11s   10.244.0.18   minikube   <none>           <none>

查看/my-test/shared.txt 文件内容

andy@hostease:~/vsproject/nfs$ kubectl exec -it standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9 -- sh
/ # ls my-test/
general.test  shared.txt    test
/ # cat my-test/shared.txt 
adding time: 06:30:18, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:21, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:28, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:31, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:38, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:41, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:48, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:51, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:58, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:31:01, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9

回到NFS存储提供Host，查看

[root@nfs /]# cd data/
[root@nfs data]# ls -lh
total 4.0K
-rw-r--r--. 1 root root   0 Jul 24 15:17 general.test
-rw-r--r--. 1 root root 830 Jul 31 14:31 shared.txt
-rw-r--r--. 1 root root   0 Jul 24 16:21 test
[root@nfs data]# cat shared.txt
adding time: 06:30:18, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:21, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:28, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:31, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:38, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:41, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:48, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:30:51, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9
adding time: 06:30:58, from standard-host-path-nfs-pvc-deployment-696c77df74-tfjvh
adding time: 06:31:01, from standard-host-path-nfs-pvc-deployment-696c77df74-6hvz9

有了NFS 持久卷，不必担心 pod 会被调度到哪个节点上，因为 NFS 卷是在所有节点上共享的，无论 pod 被调度到哪个节点，应用程序都能访问其所有数据。

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