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# 一、PVC简介
PVC是资源的申请，用来声明对存储空间、访问模式、存储类别需求信息，如下为PVC的资源文件
```yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc
  namespace: dev
spec:
  accessModes:  # 访问模式
  selector:  # 采用标签对PV选择
  storageClassName:  # 存储类别
  resources:  # 请求空间
    requests:
      storage: 2Gi
```
PVC的关键配置参数说明
* 访问模式（accessModes）
用于描述用户应用对存储资源的访问权限
* 选择条件
通过Label Selecot的设置，可使PVC对于系统中已存在的PV进行筛选
* 存储类别
PVC在定义时可以设定需要的后端存储的类别，只有设置了该class的PV才能被系统选出
* 资源请求
对存储资源的请求

# 二、PVC实例
编写pvc.yaml文件，申请PV，内容如下：
```yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc1
  namespace: dev
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1Gi

---

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc2
  namespace: dev
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1Gi

---

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc3
  namespace: dev
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1Gi
```
使用如下命令创建pvc
```bash
[root@master volume]# kubectl apply -f pvc.yaml
namespace/dev created
persistentvolumeclaim/pvc1 created
persistentvolumeclaim/pvc2 created
persistentvolumeclaim/pvc3 created
[root@master volume]#
```
查看创建好的pvc资源，如下：
```bash
[root@master volume]# kubectl get pvc -n dev
NAME   STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc1   Bound    pv2      2Gi        RWX                           2m15s
pvc2   Bound    pv1      2Gi        RWX                           2m15s
pvc3   Bound    pv3      2Gi        RWX                           2m15s
[root@master volume]#
```
此时再查看一下PV，如下，已经存在绑定关系了
```bash
[root@master volume]# kubectl get pv
NAME            CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                         STORAGECLASS   REASON   AGE
auth-mysql-pv   10Gi       RWO            Retain           Bound    lbsheng/auth-mysql-pv-claim   manual                  8d
pv1             2Gi        RWX            Retain           Bound    dev/pvc2                                              31h
pv2             2Gi        RWX            Retain           Bound    dev/pvc1                                              31h
pv3             2Gi        RWX            Retain           Bound    dev/pvc3                                              31h
[root@master volume]#
```
在创建pod的yaml中申请pvc，编辑pod_pvc.yaml文件，内容如下：
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod1
  namespace: dev
spec:
  containers:
  - name: busybox
    image: busybox:1.30
    command: ["/bin/sh","-c","while true;do echo pod1 >> /root/out.txt;sleep 10;done;"]
    volumeMounts:
    - name: volume
      mountPath: /root/
  volumes:
  - name: volume
    persistentVolumeClaim:
      claimName: pvc1
      readOnly: false
```
使用如下命令创建资源：
```bash
[root@master volume]# kubectl apply -f pod_pvc.yaml
pod/pod1 created
[root@master volume]#
```
根据上面的创建的资源可以发现，pvc1使用的是pv2，而pv2挂载的是nfs中的/root/data/pv2的目录，此时查看目录如下，已经存在out.txt文件了
```bash
[root@master volume]# ls /root/data/pv2
out.txt
[root@master volume]#
```
使用tail命令可以发现out.txt文件中的内容
```bash
[root@master volume]# tail -f /root/data/pv2/out.txt
pod1
pod1
pod1
pod1
pod1
pod1
pod1
pod1
pod1
pod1
pod1

```
如下删除pod以及pvc
```bash
[root@master volume]# kubectl delete -f pod_pvc.yaml
pod "pod1" deleted
[root@master volume]# kubectl delete -f pvc.yaml
namespace "dev" deleted
persistentvolumeclaim "pvc1" deleted
persistentvolumeclaim "pvc2" deleted
persistentvolumeclaim "pvc3" deleted
[root@master volume]#
```
此时再查看pv可以发现此时pv的绑定关系已经释放了
```bash
[root@master volume]# kubectl get pv
NAME            CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS     CLAIM                         STORAGECLASS   REASON   AGE
auth-mysql-pv   10Gi       RWO            Retain           Bound      lbsheng/auth-mysql-pv-claim   manual                  8d
pv1             2Gi        RWX            Retain           Released   dev/pvc2                                              31h
pv2             2Gi        RWX            Retain           Released   dev/pvc1                                              31h
pv3             2Gi        RWX            Retain           Released   dev/pvc3                                              31h
[root@master volume]#

```

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