第8章 Volume & PersistentVolume(数据卷)

一. 本地卷

• Kubernetes中的Volume提供了在容器中挂载外部存储的能力。
• Pod设置卷来源（spec.volume）和挂载点（spec.containers.volumeMounts）两个信息后才可以使用相应的Volume。

**卷来源: **
① 本地卷: emptyDir、hostpath
② 网络卷：NFS、cephfs ....

1. emptyDir：

创建一个空卷，挂载到Pod中的容器。Pod删除该卷也会被删除。应用场景：Pod中容器之间数据共享

# cat emptyDir-pod.yaml
apiVersion: v1 
kind: Pod
metadata:
  name: emptydir-pod
spec:
  containers:
  - name: write
    image: centos
    command: ["bash","-c","for i in {1..100};do echo $i >> /data/hello;sleep 1;done"]
    volumeMounts:
      - name: data
        mountPath: /data

  - name: read
    image: centos
    command: ["bash","-c","tail -f /data/hello"]
    volumeMounts:
      - name: data
        mountPath: /data

  volumes:
  - name: data
    emptyDir: {}

# kubectl create -f emptyDir-pod.yaml
# kubectl log emptydir-pod -c read

2. hostpath

挂载Node文件系统上文件或者目录到Pod中的容器。应用场景：Pod中容器需要访问宿主机文件

# cat hostpath-pod.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: hostpath-pod
spec:
  containers:
  - name: busybox
    image: busybox
    args:
    - /bin/sh
    - -c
    - sleep 36000
    volumeMounts:
    - name: data
      mountPath: /data
  volumes:
  - name: data
    hostPath:
      path: /tmp
      type: Directory

# kubectl create -f hostpath-pod.yaml
# kubectl get pods -o wide
NAME                                READY   STATUS    RESTARTS   AGE     IP            NODE          NOMINATED NODE
hostpath-pod                        1/1     Running   0          2m49s   172.17.31.6   10.40.6.210   

###到10.40.6.210 Node创建一个/tmp/test.txt
# echo 'test' > /tmp/test.txt
# kubectl exec -it hostpath-pod sh
/ # cat /data/test.txt
test

二. 网络卷

1. NFS 网络存储

要挂载NFS共享目录的Node节点必须安装nfs客户端: yum install nfs-utils -y
NFS服务端 10.40.6.214 安装：yum install nfs-utils -y
服务端配置并启动守护进程：

# cat /etc/exports
/data/nfs *(rw,no_root_squash)

# mkdir /data/nfs -p
# systemctl start nfs

yaml配置文件：

# cat nfs-pod.yaml 
apiVersion: apps/v1beta1 
kind: Deployment 
metadata:
  name: nginx-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx  
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
        ports:
        - containerPort: 80
      volumes:
      - name: www
        nfs:
          server: 10.40.6.214
          path: /data/nfs

# kubectl create -f nfs-pod.yaml 
deployment.apps/nginx-deployment created

# kubectl get pod
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-759cdcdc87-sz88v   1/1     Running   0          74s
nginx-deployment-759cdcdc87-w8f6l   1/1     Running   0          74s

###到 10.40.6.214 /data/nfs 目录下创建index.html
# cat index.html 
hello world!

###进入容器查看index.html
# kubectl exec -it nginx-deployment-759cdcdc87-sz88v bash
[root@nginx-deployment-759cdcdc87-sz88v nginx]# cat /usr/share/nginx/html/index.html
hello world!