K8s复习笔记2-Volume

1. Volume

将数据和镜像解耦,以及容器间数据共享.不将数据打包到镜像中可以减小镜像大小.
k8s抽象出一个对象,用来保存数据.
常用的卷有:
emptyDir: 本地临时卷,容器删除数据跟着删除
hostPath: 本地卷,容器删除数据不被删除
nfs: nfs共享卷,容器删除数据不被删除
configmap: 配置文件
其他:https://kubernetes.io/zh-cn/docs/concepts/workloads/controllers/deployment/#scaling-a-deployment

1.1 emptyDir

当pod被创建时,会先创建emptyDir卷.只要该pod在该节点上运行,这个卷就会一直存在.被创建的时候这个卷是空的.pod中的容器可以读写该emptyDir卷中的文件.当pod被删除时,emptyDir将被永久删除.可以放一些缓存或日志等不重要的文件.

#apiVersion: extensions/v1beta1
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels: #rs or deployment
      app: ng-deploy-80
  template:
    metadata:
      labels:
        app: ng-deploy-80
    spec:
      containers:
      - name: ng-deploy-80
        image: nginx 
        ports:
        - containerPort: 80
        volumeMounts:
        - mountPath: /cache
          name: empty-volume
      volumes:
      - name: empty-volume
        emptyDir: {
    
    }

pod创建后写入文件到/cache/abc.txt

刚创建的时候目录是空的,写入文件后可以在node节点上读取到该文件内容.

当pod被删除后,emptyDir一并消失

1.2 hostPath

和docker的-v效果比较类似,即使容器被删除,该路径下的数据任然会被保存下来.但发生节点切换就会造成数据丢失.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: ng-deploy-80
  template:
    metadata:
      labels:
        app: ng-deploy-80
    spec:
      containers:
      - name: ng-deploy-80
        image: nginx 
        ports:
        - containerPort: 80
        volumeMounts:
        - mountPath: /data
          name: cache-volume
      volumes:
      - name: cache-volume
        hostPath:
          path: /tmp/cache

创建hostPath

1.3 nfs

1.3.1 nfs 环境准备

apt update
apt install nfs-server
mkdir /data/k8s/ -p
echo '/data/k8s *(rw,sync,no_root_squash)' >> /etc/exports
systemctl enable --now nfs-server
systemctl restart nfs-server

1.3.2 node节点测试是否可以正常访问到nfs

root@k8s-node-1:~# apt install nfs-common
root@k8s-node-1:~# showmount -e 192.168.31.109
Export list for 192.168.31.109:
/data/k8s *
root@k8s-node-1:~# 

1.3.3 单个nfs的yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: ng-deploy-80
  template:
    metadata:
      labels:
        app: ng-deploy-80
    spec:
      containers:
      - name: ng-deploy-80
        image: nginx 
        ports:
        - containerPort: 80
        volumeMounts:
        - mountPath: /usr/share/nginx/html/mysite
          name: my-nfs-volume
      volumes:
      - name: my-nfs-volume
        nfs:
          server: 192.168.31.109
          path: /data/k8s
---
apiVersion: v1
kind: Service
metadata:
  name: ng-deploy-80
spec:
  ports:
  - name: http
    port: 81
    targetPort: 80
    nodePort: 30016
    protocol: TCP
  type: NodePort
  selector:
    app: ng-deploy-80

宿主机上,nfs被挂载到容器的目录,最后被联合挂载到容器中

在pod内,nfs已经被挂载

在nfs服务器上也可以看到这个文件

一般这个都是放图片的,我们也放个图片试试看

把副本数调整成2个

可以看到新建的pod也自动挂载了相同的内容,数据也是完全相同的

1.3.3 多个nfs的yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: ng-deploy-80
  template:
    metadata:
      labels:
        app: ng-deploy-80
    spec:
      containers:
      - name: ng-deploy-80
        image: nginx 
        ports:
        - containerPort: 80
        volumeMounts:
        - mountPath: /usr/share/nginx/html/html
          name: nfs-volume-html
        - mountPath: /usr/share/nginx/html/jpg
          name: nfs-volume-jpg
        - mountPath: /usr/share/nginx/html/yml
          name: nfs-volume-yml
      volumes:
      - name: nfs-volume-html
        nfs:
          server: 192.168.31.109
          path: /data/k8s
      - name: nfs-volume-jpg
        nfs:
          server: 192.168.31.110
          path: /data/k8s
      - name: nfs-volume-yml
        nfs:
          server: 192.168.31.104
          path: /data/k8s
---
apiVersion: v1
kind: Service
metadata:
  name: ng-deploy-80
spec:
  ports:
  - name: http
    port: 81
    targetPort: 80
    nodePort: 30016
    protocol: TCP
  type: NodePort
  selector:
    app: ng-deploy-80

分别在192.168.31.109,192.168.31.110,192.168.31.104创建目录,并映射到pod中不同的目录


yaml被当普通文件下载

最后实现pod挂载3个不同的nfs路径

1.4 Configmap

存在的意义:使得镜像和配置解耦,将配置信息放入configmap,在pod的对象中导入configmap,实现配置导入

apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-config
data:
 default: |
    server {
       listen       80;
       server_name  www.mysite.com;
       index        index.html;
       location / {
           root /data/nginx/html;
           if (!-e $request_filename) {
               rewrite ^/(.*) /index.html last;
           }
       }
    }
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: ng-deploy-80
  template:
    metadata:
      labels:
        app: ng-deploy-80
    spec:
      containers:
      - name: ng-deploy-80
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - mountPath: /data/nginx/html
          name: my-nfs-volume
        - name: nginx-config
          mountPath:  /etc/nginx/conf.d/
      volumes:
      - name: nginx-config
        configMap:
          name: nginx-config
          items:
             - key: default
               path: mysite.conf
      - name: my-nfs-volume
        nfs:
          server: 192.168.31.109
          path: /data/k8sdata
---
apiVersion: v1
kind: Service
metadata:
  name: ng-deploy-80
spec:
  ports:
  - name: http
    port: 81
    targetPort: 80
    nodePort: 30019
    protocol: TCP
  type: NodePort
  selector:
    app: ng-deploy-80

此时访问不存在的页面,会直接将首页返回.
明显configmap配置已经生效

root@k8s-master-01:~/yml# curl 192.168.31.113:30019
in nfs node
root@k8s-master-01:~/yml# curl 192.168.31.113:30019/dak.dkaj
in nfs node
root@k8s-master-01:~/yml# curl 192.168.31.113:30019/dak.jpg
in nfs node

再看下pod下文件,可以看到/etc/nginx/conf.d/mysite.conf的内容正是configmap中default的内容

root@k8s-master-01:~/yml# kubectl exec -it nginx-deployment-7c94b5fcb7-rnj7g sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
# cat /etc/nginx/nginx.conf

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log notice;
pid        /var/run/nginx.pid;


events {
    
    
    worker_connections  1024;
}


http {
    
    
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    include /etc/nginx/conf.d/*.conf;
}
# cat /etc/nginx/conf.d/mysite.conf
server {
    
    
   listen       80;
   server_name  www.mysite.com;
   index        index.html;
   location / {
    
    
       root /data/nginx/html;
       if (!-e $request_filename) {
    
    
           rewrite ^/(.*) /index.html last;
       }
   }
}

1.5 pv/pvc

PersistentVolume/PersistentVvolumeClaim
实现pod和存储的解耦,这样修改storage的时候就不需要修改pod,只需要修改pv和pvc的配置就可以.也可以实现存储和应用的权限隔离.
pv和存储对接,全局资源,不需要指定namespace.
pvc和pod对接,需要指定namespace

这部分后续和ceph一起更新