k8s pvc详解-Toy模板网

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一、概述

PVC 的全称是：PersistentVolumeClaim（持久化卷声明），PVC 是用户存储的一种声明，PVC 和 Pod 比较类似，Pod 消耗的是节点，PVC 消耗的是 PV 资源，Pod 可以请求 CPU 和内存，而 PVC 可以请求特定的存储空间和访问模式。对于真正使用存储的用户不需要关心底层的存储实现细节，只需要直接使用 PVC 即可。

PVC作为用户对存储资源的需求申请，主要涉及存储空间请求、访问模式、 PV选择条件和存储类别等信息的设置。

二、参数解释

创建pvc，如下：

---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: test-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi
  storageClassName: nfs
  volumeMode: Filesystem

accessModes：访问模式

PVC也可以设置访问模式，用于描述用户应用对存储资源的访问权限，其设置参数和pv一致
resources：资源请求

描述对存储的请求数量，通过 resources.requests.storage字段设置需要的存储空间大小。
volumeMode：存储卷格式，用于描述用户使用的PV存储卷模式，包括文件系统（Filesystem）和块设备 (Block)，与pv一致。
storageClassName：存储类型

在创建pvc时需要指定后端存储类型，以减少对后端存储详细信息的依赖。
- 如果系统中存在一个DefaultStorageClass，可以在创建pvc的时候不指定storageclassname，系统会自动使用默认的存储类型。
- 如果将多个StorageClass都定义为default，则由于不唯一，系统将无法创建PVC。

三、pod使用pvc

编辑配置文件，如下：

---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: test-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi
  storageClassName: nfs
  volumeMode: Filesystem 
 
---
apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  - name: myfrontend
    image: docker.io/library/centos:7
    command: ["init"]
    imagePullPolicy: IfNotPresent
    volumeMounts:
    - mountPath: /data                                                                         name: test-path
  volumes:
  - name: test-path
    persistentVolumeClaim:
      claimName: test-pvc
      
      
执行创建命令如下：
kubectl apply -f pod.yaml
[root@node1 yaml]# kubectl get po -o wide 
NAME                                      READY   STATUS    RESTARTS   AGE   IP             NODE    NOMINATED NODE   READINESS GATES
mypod                                     1/1     Running   0          4s    10.233.96.10   node2   <none>           <none>

进入pod查看挂载的目录，如下：
[root@node1 yaml]# kubectl exec -it mypod bash 
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
[root@mypod /]# ls
anaconda-post.log  bin  data  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
[root@mypod /]# ll 
total 12
-rw-r--r--   1 root root 12114 Nov 13  2020 anaconda-post.log
lrwxrwxrwx   1 root root     7 Nov 13  2020 bin -> usr/bin
drwxrwxrwx   2 root root     6 Jun  5 06:27 data    ####目录被自动挂载
drwxr-xr-x   5 root root   360 Jun  5 06:34 dev
drwxr-xr-x   1 root root    41 Jun  5 06:34 etc
drwxr-xr-x   2 root root     6 Apr 11  2018 home

四、pv、pvc状态变化

不同情况下，PV和PVC的状态变化如下：
k8s pvc,k8s,k8s
具体操作如下：文章来源地址https://www.toymoban.com/news/detail-612013.html

#############################
1:创建pv
---
apiVersion: v1                         
kind: PersistentVolume                 
metadata:                              
  name: pv-nfs                         
spec:                                  
  accessModes:                         
  - ReadWriteOnce                      
  capacity:                            
    storage: 2Gi                       
  nfs:                                 
    path: /data/                       
    server: 192.168.5.79               
  persistentVolumeReclaimPolicy: Retain                                                                                                                                    
  storageClassName: nfs                
  volumeMode: Filesystem
  
[root@node1 yaml]# kubectl apply -f  nfs-pv.yaml 
persistentvolume/pv-nfs created
[root@node1 yaml]# 
[root@node1 yaml]# kubectl get pv  | grep pv-nfs
pv-nfs                                     2Gi        RWO            Retain           Available                                            nfs                     23s
[root@node1 yaml]#
此时查看pv的状态为Available


##############################
2：创建pvc,如下：
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-nfs
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi
  storageClassName: nfs
  volumeMode: Filesystem
  
[root@node1 yaml]# kubectl apply -f  pvc.yaml 
persistentvolumeclaim/pvc-nfs created
[root@node1 yaml]# kubectl get pvc       ###正常是状态先为pending，然后是Bound
NAME         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc-nfs      Bound    pv-nfs                                     2Gi        RWO            nfs            7s

############################
3：删除pv,查看pvc的状态
[root@node1 yaml]# kubectl delete pv pv-nfs
persistentvolume "pv-nfs" delete      ####会一直卡在这里

打开新的终端，查看pv状态已经是Terminating
[root@node1 ~]# kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS        CLAIM                                    STORAGECLASS   REASON   AGE
pv-nfs                                     2Gi        RWO            Retain           Terminating   default/pvc-nfs                          nfs                     11m

出现删除不掉问题的主要原因是pv已经和pvc绑定，pv内部有kubernetes.io/pv-protection这个参数进行保护，编辑pv,删除这个参数，kubectl edit  pv pv-nfs，如下：

apiVersion: v1
kind: PersistentVolume
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"PersistentVolume","metadata":{"annotations":{},"name":"pv-nfs"},"spec":{"accessModes":["ReadWriteOnce"],"capacity":{"storage":"2Gi"},"nfs":{"path":"/data/","server":"192.168.5.79"},"persistentVolumeReclaimPolicy":"Retain","storageClassName":"nfs","volumeMode":"Filesystem"}}
    pv.kubernetes.io/bound-by-controller: "yes"
  creationTimestamp: "2023-06-05T08:12:28Z"
  deletionGracePeriodSeconds: 0
  deletionTimestamp: "2023-06-05T08:23:27Z"
 # finalizers:    ####将此参数删除
 # - kubernetes.io/pv-protection
  name: pv-nfs
  resourceVersion: "9420641"
  uid: cb3b7c54-b8e9-4132-b273-16e9415ae643
spec:
  accessModes:
  - ReadWriteOnce
  capacity:
    storage: 2Gi

再次查看pv已经被删除了，此时pvc状态为Lost，如下：
[root@node1 yaml]# kubectl get pvc
NAME         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc-nfs      Lost     pv-nfs                                     0                         nfs            13m

解决方式，将删除的pv进行重新创建，pvc和pv的状态都会变成Bound
[root@node1 yaml]# kubectl apply -f  nfs-pv.yaml 
persistentvolume/pv-nfs created
[root@node1 yaml]# kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                                    STORAGECLASS   REASON   AGE
pv-nfs                                     2Gi        RWO            Retain           Bound    default/pvc-nfs                          nfs                     4s
[root@node1 yaml]# kubectl get pvc
NAME         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc-nfs      Bound    pv-nfs                                     2Gi        RWO            nfs            15m

############################
4：删除pvc，查看pv状态变化，如下：
[root@node1 yaml]# kubectl delete pvc pvc-nfs
persistentvolumeclaim "pvc-nfs" deleted
[root@node1 yaml]# kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS     CLAIM                                    STORAGECLASS   REASON   AGE
pv-nfs                                     2Gi        RWO            Retain           Released   default/pvc-nfs                          nfs                     84s

此时的pv状态已经是released，但如果此时在创建新的pvc，能够进行pv和pvc的绑定呢，大答案是不行的，因为pvc只能和Available状态的pv进行绑定。
在pv变成released的时候，查看claimRef属性，其中依然保留着PVC的绑定信息，如下：
[root@node1 yaml]# kubectl get pv pv-nfs  -o yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"PersistentVolume","metadata":{"annotations":{},"name":"pv-nfs"},"spec":{"accessModes":["ReadWriteOnce"],"capacity":{"storage":"2Gi"},"nfs":{"path":"/data/","server":"192.168.5.79"},"persistentVolumeReclaimPolicy":"Retain","storageClassName":"nfs","volumeMode":"Filesystem"}}
    pv.kubernetes.io/bound-by-controller: "yes"
  creationTimestamp: "2023-06-05T08:29:29Z"
  finalizers:
  - kubernetes.io/pv-protection
  name: pv-nfs
  resourceVersion: "9421489"
  uid: 09c62907-7fa3-491f-bb48-656003581c8f
spec:
  accessModes:
  - ReadWriteOnce
  capacity:
    storage: 2Gi
  claimRef:       ####查看此处，保留了pvc的绑定信息
    apiVersion: v1
    kind: PersistentVolumeClaim
    name: pvc-nfs
    namespace: default
    resourceVersion: "9421099"
    uid: 15935386-4b7b-4b97-88b3-2bece1ed6ea9
  nfs:
    path: /data/
    server: 192.168.5.79
  persistentVolumeReclaimPolicy: Retain
  storageClassName: nfs
  volumeMode: Filesystem
status:
  phase: Released
[root@node1 yaml]# 

解决方式是导出pv的信息进行备份，然后删除claimRef出的内容，如下：
[root@node1 yaml]# kubectl get pv pv-nfs  -o yaml > pv.yaml
[root@node1 yaml]# kubectl edit pv pv-nfs
---
apiVersion: v1
kind: PersistentVolume
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"PersistentVolume","metadata":{"annotations":{},"name":"pv-nfs"},"spec":{"accessModes":["ReadWriteOnce"],"capacity":{"storage":"2Gi"},"nfs":{"path":"/data/","server":"192.168.5.79"},"persistentVolumeReclaimPolicy":"Retain","storageClassName":"nfs","volumeMode":"Filesystem"}}
    pv.kubernetes.io/bound-by-controller: "yes"
  creationTimestamp: "2023-06-05T08:29:29Z"
  finalizers:
  - kubernetes.io/pv-protection
  name: pv-nfs
  resourceVersion: "9421489"
  uid: 09c62907-7fa3-491f-bb48-656003581c8f
spec:
  accessModes:
  - ReadWriteOnce
  capacity:
    storage: 2Gi
  nfs:
    path: /data/
    server: 192.168.5.79
  persistentVolumeReclaimPolicy: Retain
  storageClassName: nfs
  volumeMode: Filesystem
status:
  phase: Released
persistentvolume/pv-nfs edited
[root@node1 yaml]# kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM                                    STORAGECLASS   REASON   AGE
pv-nfs                                     2Gi        RWO            Retain           Available                                            nfs                     10m
再次查看pv状态变为Available，此在创建pvc，pv/pvc状态都为Bound,如下：
[root@node1 yaml]# kubectl apply -f   pvc.yaml 
persistentvolumeclaim/pvc-nfs created
[root@node1 yaml]# kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                                    STORAGECLASS   REASON   AGE
pv-nfs                                     2Gi        RWO            Retain           Bound    default/pvc-nfs                          nfs                     12m
[root@node1 yaml]# kubectl get pvc
NAME         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
pvc-nfs      Bound    pv-nfs                                     2Gi        RWO            nfs            7s

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