存储卷与数据持久化（一）

 

(1) emptyDir存储卷：临时存储卷

相当于pod对象上的一个临时目录，pod对象启动时创建，移除时一并删除

下面创建一个emptyDir存储卷示例

[root@k8s-master01 yaml]# cat volumes-emptydir-demo.yaml 
apiVersion : v1
kind: Pod
metadata:
  name: volumes-emptydir-demo
  namespace: storage
spec:
  initContainers:
  - name: config-file-downloader
    image: ikubernetes/admin-box
    imagePullPolicy: IfNotPresent
    command: ["/bin/sh","-c","wget -O /data/envoy.yaml https://raw.githubusercontent.com/iKubernetes/Kubernetes_Advanced_Practical_2rd/master/chapter4/envoy.yaml"]
    volumeMounts:
    - name: config-file-store
      mountPath: /data
  containers:
  - name: envoy
    image: envoyproxy/envoy-alpine:v1.13.1
    command: ["/bin/sh","-c"]
    args: ["envoy -c /etc/envoy/envoy.yaml"]
    volumeMounts:
    - name: config-file-store
      mountPath: /etc/envoy
      readOnly: true
  volumes:
  - name: config-file-store
    emptyDir:                 #该存储卷嵌套定义在.spec.volumes.emptyDir字段中，可用字段主要有2个：如下
      medium: Memory          #该字段表示此目录所存在的存储介质类型：可用值为default或者Menory，默认是default。
      sizeLimit: 16Mi         #该字段表示存储卷的空间限额，默认值为nil；表示不限制；不过，在medium字段为memory时，建议务必定义此限额。

[root@k8s-master01 yaml]# kubectl apply -f volumes-emptydir-demo.yaml -n storage
pod/volumes-emptydir-demo created
[root@k8s-master01 yaml]# kubectl get pods -n storage -o wide
NAME                    READY   STATUS    RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES
volumes-emptydir-demo   1/1     Running   0          3s    10.244.3.15   k8s-node03   <none>           <none>

[root@k8s-master01 yaml]# kubectl exec volumes-emptydir-demo -n storage -- netstat -tnl
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       
tcp        0      0 0.0.0.0:9901            0.0.0.0:*               LISTEN      
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      

[root@k8s-master01 yaml]# podIP=$(kubectl get pods/volumes-emptydir-demo -n storage -o jsonpath={.status.podIP})
[root@k8s-master01 yaml]# curl $podIP:9901/listeners
listener_0::0.0.0.0:80

[root@k8s-master01 yaml]# kubectl describe pods volumes-emptydir-demo -n storage
Name:         volumes-emptydir-demo
Namespace:    storage
Priority:     0
Node:         k8s-node03/10.122.138.247
Start Time:   Thu, 19 Aug 2021 09:15:08 +0800
Labels:       <none>
Annotations:  <none>
Status:       Running
IP:           10.244.3.15
IPs:
  IP:  10.244.3.15
Init Containers:
  config-file-downloader:
    Container ID:  docker://b34a8f69a5e0ff2c4404db02e6d2a14b8721cd9572e87d32cb6ba262ed4291ed
    Image:         ikubernetes/admin-box
    Image ID:      docker-pullable://ikubernetes/admin-box@sha256:56e2413d2bcc279c6667d36fa7dfc7202062a933d0f69cd8a1769b68e2155bbf
    Port:          <none>
    Host Port:     <none>
    Command:
      /bin/sh
      -c
      wget -O /data/envoy.yaml https://raw.githubusercontent.com/iKubernetes/Kubernetes_Advanced_Practical_2rd/master/chapter4/envoy.yaml
    State:          Terminated
      Reason:       Completed
      Exit Code:    0
      Started:      Thu, 19 Aug 2021 09:15:09 +0800
      Finished:     Thu, 19 Aug 2021 09:15:09 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:                                                                          #挂载信息如下：
      /data from config-file-store (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-mcbbq (ro)
Containers:
  envoy:
    Container ID:  docker://9a430194cb65b164edb1a7d53be1b66a8f7970fe2d0a2108166bacacb8d250dc
    Image:         envoyproxy/envoy-alpine:v1.13.1
    Image ID:      docker-pullable://envoyproxy/envoy-alpine@sha256:f9a8a35268d68c9cac9fad66f30778038385093c87516083a69be6464488811b
    Port:          <none>
    Host Port:     <none>
    Command:
      /bin/sh
      -c
    Args:
      envoy -c /etc/envoy/envoy.yaml
    State:          Running
      Started:      Thu, 19 Aug 2021 09:15:10 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:                                                                           #挂载信息如下：
      /etc/envoy from config-file-store (ro)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-mcbbq (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  config-file-store:
    Type:       EmptyDir (a temporary directory that shares a pod's lifetime)
    Medium:     Memory
    SizeLimit:  16Mi
  default-token-mcbbq:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-mcbbq
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                 node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age   From                 Message
  ----    ------     ----  ----                 -------
  Normal  Scheduled  22m                        Successfully assigned storage/volumes-emptydir-demo to k8s-node03
  Normal  Pulled     22m   kubelet, k8s-node03  Container image "ikubernetes/admin-box" already present on machine
  Normal  Created    22m   kubelet, k8s-node03  Created container config-file-downloader
  Normal  Started    22m   kubelet, k8s-node03  Started container config-file-downloader
  Normal  Pulled     22m   kubelet, k8s-node03  Container image "envoyproxy/envoy-alpine:v1.13.1" already present on machine
  Normal  Created    22m   kubelet, k8s-node03  Created container envoy
  Normal  Started    22m   kubelet, k8s-node03  Started container envoy

 

 

（二）hostPath存储卷

hostPath存储卷插件是将工作节点上某个文件系统的目录或者文件关联到pod上的一种存储类型，其数据具有同工作节点生命周期一样的持久性。hostPath存储卷使用的是工作节点本地上的存储空间，所以仅适用于特定情况下的存储卷使用需求。hostPath存储卷在运行有管理任务的系统级pod资源，以及pod资源需要访问节点上的文件时尤其有用。

 

（三）网络存储卷

下面的资源清单中，容器镜像文件默认会以redis用户（UID是999）运行redis-server进程，并且将数据持久保存在此容器文件系统上的/data目录上，因而需要确保UID为999的用户有权限读写该目录，于此对应，NFS服务器上用于该pod对象的存储卷的导出目录/data/redis目录也需要确保UID为999的用户有权限读写该目录，所以需要在NFS服务器（10.122.138.244） 创建该用户，并且uid=999,。

在10.122.138.244上：

mkdir -p  /data/redis

useradd -u 999 redis

chown redis /data/redis

安装nfs服务器端：

yum install -y nfs-utils rpcbind

systemctl start rpcbind.service  &&  systemctl start nfs.service

systemctl enable rpcbind.service  &&  systemctl enable nfs.service

创建nfs配置文件

vim /etc/exports

/data/redis  10.122.138.244/24(rw,no_root_squash)  10.244.0.0/16(rw,no_root_squash) 

exportfs -rv  重新加载配置文件，立即生效

showmount  -e  查看挂载

然后在工作节点上安装客户端工具

yum install -y  nfs-utils 

systemctl start nfs-utils 

systemctl enable nfs-utils

 

[root@k8s-master01 yaml]# cat volumes-nfs-demo.yaml 
apiVersion : v1
kind: Pod
metadata:
  name: volumes-nfs-demo
  labels:
    app: redis
spec:
  containers:
  - name: redis
    image: redis:alpine
    ports:
    - containerPort: 6379
      name: redisport
    securityContext:
      runAsUser: 999
    volumeMounts:
    - mountPath: /data
      name: redisdata
  volumes:
    - name: redisdata
      nfs:
        server: 10.122.138.244
        path: /data/redis
        readOnly: false
[root@k8s-master01 yaml]# kubectl get pod/volumes-nfs-demo.yaml -o wide
Error from server (NotFound): pods "volumes-nfs-demo.yaml" not found
[root@k8s-master01 yaml]# kubectl get pod/volumes-nfs-demo -o wide
NAME               READY   STATUS    RESTARTS   AGE   IP            NODE         NOMINATED NODE   READINESS GATES
volumes-nfs-demo   1/1     Running   0          87s   10.244.3.16   k8s-node03   <none>           <none>
[root@k8s-master01 yaml]# kubectl exec -it volumes-nfs-demo -- redis-cli
127.0.0.1:6379> set mykey "hello k8s-master"
OK
127.0.0.1:6379> get mykey
"hello k8s-master"
127.0.0.1:6379> BGSAVE
Background saving started
127.0.0.1:6379> EXIT
[root@k8s-master01 yaml]# kubectl delete pod/volumes-nfs-demo
pod "volumes-nfs-demo" deleted
[root@k8s-master01 yaml]# kubectl apply -f volumes-nfs-demo.yaml
pod/volumes-nfs-demo created
[root@k8s-master01 yaml]# kubectl exec -it volumes-nfs-demo -- redis-cli
error: unable to upgrade connection: container not found ("redis")
[root@k8s-master01 yaml]# kubectl exec -it volumes-nfs-demo -- redis-cli
127.0.0.1:6379> get mykey
"hello k8s-master"
127.0.0.1:6379>    #上面的命令显示此前创建的键nykey及其数据在pod对象删除并重新创建后依然存在，表明删除pod对象后，其关联的外部存储设备及其数据并不会一起被删除，因此才具有了跨pod生命周期的数据持久性；若要删除pod后清除数据，需要管理员通过管理接口手动进行。