8、kubernetes之存储卷资源

一、存储卷的类型

• emptyDir：在宿主机上分一块内存空间给pod当做存储空间
• hostPath：在宿主机上分一块磁盘空间给pod当做存储空间
• 网络存储：
  • SAN：iSCSI，FC
  • NAS：nfs，cifs
  • 分布式存储：glusterfs，rbd，cephfs，...
  • 云存储：EBS，Azure，Disk

# kubectl explain  pods.spec.volumes  #查看k8s支持的存储

二、emptyDir

apiVersion: v1
kind: Pod
metadata:
  name: pod-vol-demo
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    volumeMounts:
    - name: htmlvomumes
      mountPath: /data/web/html2/
  volumes:
    - name: htmlvomumes
      emptyDir: 
        medium: ""  #使用宿主机内存当做磁盘挂载
        sizeLimit: "1024"  #限制使用的内存

三、hostPath

apiVersion: v1
kind: Pod
metadata:
  name: pod-vol-hostpath
  namespace: default
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    volumeMounts:
    - name: html
      mountPath: /usr/share/nginx/html/
  volumes:
  - name: html
    hostPath:
      path: /data/pod/volume1  #node节点路径
      type: DirectoryOrCreate  #文件夹不存在则创建

四、nfs

• 搭建/测试nfs-server

# yum install nfs-utils -y
# mkdir /data/volumes/
# vim /etc/exports
/data/volumes   192.168.100.0/24(rw,no_root_squash)
# systemctl start nfs
# systemctl enable nfs

# mount -t nfs 192.168.100.1:/data/volumes /mnt/

apiVersion: v1
kind: Pod
metadata:
  name: pod-vol-nfs
  namespace: default
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    volumeMounts:
    - name: html
      mountPath: /usr/share/nginx/html/
  volumes:
  - name: html
    nfs:
      path: /data/volumes
      server: 192.168.100.1

五、pv和pvc

# kubectl explain pv
# kubectl explain pvc
# kubectl get pv
# kubectl get pvc

1、提前准备PV的方式

• 准备存储空间

# mkdir -p /data/volumes/v{1,2,3,4,5}
# vim /etc/exports
/data/volumes/v1        192.168.100.0/24(rw,no_root_squash)
/data/volumes/v2        192.168.100.0/24(rw,no_root_squash)
/data/volumes/v3        192.168.100.0/24(rw,no_root_squash)
/data/volumes/v4        192.168.100.0/24(rw,no_root_squash)
/data/volumes/v5        192.168.100.0/24(rw,no_root_squash)
# exportfs -arv
# showmount -e

• 创建pv

访问模型（accessModes <[]string>）：https://kubernetes.io/docs/concepts/storage/persistent-volumes/#access-modes

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv001
  labels:
    name: pv001
spec:
  nfs:
    path: /data/volumes/v1
    server: 192.168.100.1
  accessModes: ["ReadWriteMany","ReadWriteOnce"]
  capacity:
    storage: 3Gi
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv002
  labels:
    name: pv002
spec:
  nfs:
    path: /data/volumes/v2
    server: 192.168.100.1
  accessModes: ["ReadWriteOnce"]
  capacity:
    storage: 5Gi
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv003
  labels:
    name: pv003
spec:
  nfs:
    path: /data/volumes/v3
    server: 192.168.100.1
  accessModes: ["ReadWriteOnce"]
  capacity:
    storage: 50Gi

• 创建pvc

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc001
  namespace: default
spec:
  accessModes: ["ReadWriteOnce"]
  resources: 
    requests: 
      storage: 6Gi  #要求绑定大于6G的pv
---
apiVersion: v1
kind: Pod
metadata:
  name: pod-vol-pvc
  namespace: default
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    volumeMounts:
    - name: html
      mountPath: /usr/share/nginx/html/
  volumes:
  - name: html
    persistentVolumeClaim:
      claimName: pvc001

2、按pvc需要自动创建pv

• 需要支持resfull风格api的存储来请求动态创建存储，实现动态请求创建pv

六、configmap和secret

• secret和configmap是两个特殊的存储卷，用于用户将集群外的配置注入pod
• secret和configmap的功能相同，configmap以明文存储，secret是用base64编码存放

配置容器化应用的方式：

1. 自定义命令行参数：args: []
2. 把配置文件直接copy进镜像
3. 环境变量加载配置
   1. cloud native的应用程序一般可通过环境变量加载配置
   2. 通过entrypoint脚本来预处理变量为配置文件中的配置信息
4. 存储卷

# kubectl explain cm

• 命令行直接创建cm

# kubectl create configmap nginx-config --from-literal=nginx_port=80 --from-literal=server_name=myapp.dongfei.tech
# kubectl get cm
# kubectl describe cm nginx-config

• 命令行创建secret

# kubectl create secret generic mysql-root-password --from-literal=password=My@Pass
# kubectl get secret
# kubectl describe secret mysql-root-password
# kubectl get secret mysql-root-password -o yaml
# echo TXlAUGFzcw== |base64 -d  #解码
My@Pass

• 将配置文件创建为cm

# cat www.conf 
server {
        server_name myapp.dongfei.tech;
        listen 80;
        root /data/web/html;
}
# kubectl create configmap nginx-www --from-file=./www.conf  #不指定key则将文件名当做key，文件内容当做value

• 将cm通过环境变量注入pod

apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-1
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    env:
    - name: NGINX_SERVER_PORT
      valueFrom:
        configMapKeyRef:
          name: nginx-config
          key: nginx_port
    - name: NGINX_SERVER_NAME
      valueFrom:
        configMapKeyRef:
          name: nginx-config
          key: server_name

• 将cm通过存储卷方式以文件注入容器

apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-2
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    volumeMounts:
    - name: nginxconf
      mountPath: /etc/nginx/conf.d/
      readOnly: true
  volumes:
  - name: nginxconf
    configMap:
      name: nginx-www

• 将secret通过环境变量方式注入容器

apiVersion: v1
kind: Pod
metadata:
  name: pod-secret-1
  namespace: default
  labels:
    app: myapp
    tier: frontend
  annotations:
    dongfei.tech/created-by: "cluster admin"
spec:
  containers:
  - name: myapp
    image: dongfeimg/myapp:v1
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    env:
    - name: MYSQL_ROOT_PASSWORD
      valueFrom:
        secretKeyRef:
          name: mysql-root-password
          key: password