kubernets常见配置

subPath

定义：

为了支持单一个pod多次使用同一个volume而设计，subpath翻译过来是子路径的意思，如果是数据卷挂载在容器，指的是存储卷目录的子路径，如果是配置项configMap/Secret，则指的是挂载在容器的子路径

使用场景

1. 同一个pod中多容器挂载同一个卷时提供隔离或者一个容器有多个路径需要挂载，不指定subPath默认存储在存储卷的根目录
2. 将configMap和secret作为文件挂载到容器中而不覆盖挂载目录下的文件

数据卷挂载：一个pod中多容器

nfs-pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nfs-pod
spec:
  containers:
  - image: busybox:1.0
    imagePullPolicy: IfNotPresent
    name: busybox1
    command:
      - "/bin/sh"
    args:
      - "-c"
      - "sleep 36000"
    volumeMounts:
    - mountPath: /mnt
      name: example-volume3
  - image: busybox:1.0
    imagePullPolicy: IfNotPresent
    name: busybox2
    command:
      - "/bin/sh"
    args:
      - "-c"
      - "sleep 36000"
    volumeMounts:
    - mountPath: /opt
      name: example-volume3
  volumes:
  - name: example-volume3
    persistentVolumeClaim:
      claimName: nfs-pvc

Pod有两个名称为busybox1和busybox2的两个容器，都是调用nfs-pvc请求(所以两个容器使用相同的pv)，分别挂载容器内/mnt、/opt目录

[root@master subpath]# kubectl apply -f nfs-pod.yaml
[root@master subpath]# kubectl exec -it nfs-pod -c busybox1 -- /bin/sh 
/ # touch /mnt/aaaa

服务端存储卷根目录

[root@localhost default-nfs-pvc-pvc-74935cdc-a8f5-455b-9418-c21c10aee6c0]# pwd
/opt/default-nfs-pvc-pvc-74935cdc-a8f5-455b-9418-c21c10aee6c0
[root@localhost default-nfs-pvc-pvc-74935cdc-a8f5-455b-9418-c21c10aee6c0]# ls
aaaa

进入另一个busybox2容器，发现在opt下出现了busybox1在/mnt目录下创建的文件

[root@master subpath]# kubectl exec -it nfs-pod -c busybox2 -- /bin/sh 
~ # ls /opt/
aaaa

加上subPath参数后

apiVersion: v1
kind: Pod
metadata:
  name: nfs-pod2
spec:
  containers:
  - image: busybox:1.0
    imagePullPolicy: IfNotPresent
    name: busybox1
    command:
      - "/bin/sh"
    args:
      - "-c"
      - "sleep 36000"
    volumeMounts:
    - mountPath: /mnt
      subPath: mnt
      name: example-volume3
  - image: busybox:1.0
    imagePullPolicy: IfNotPresent
    name: busybox2
    command:
      - "/bin/sh"
    args:
      - "-c"
      - "sleep 36000"
    volumeMounts:
    - mountPath: /opt
      subPath: opt
      name: example-volume3
  volumes:
  - name: example-volume3
    persistentVolumeClaim:
      claimName: nfs-pvc2

服务端存储卷根目录下出现子目录

[root@localhost default-nfs-pvc2-pvc-65769a72-e735-4a58-aef9-63bce183ac73]# pwd
/opt/default-nfs-pvc2-pvc-65769a72-e735-4a58-aef9-63bce183ac73
[root@localhost default-nfs-pvc2-pvc-65769a72-e735-4a58-aef9-63bce183ac73]# ll
总用量 0
drwxrwxrwx. 2 root root 18 3月  17 10:58 mnt
drwxrwxrwx. 2 root root  6 3月  17 10:57 opt

进入busybox1的容器中mnt目录下创建文件

[root@master subpath]# kubectl exec -it nfs-pod2 -c busybox1 -- /bin/sh 
/ # touch /mnt/bbbb

此时进入busybox2的容器的opt目录下，并不会出现bbbb文件

[root@master subpath]# kubectl exec -it nfs-pod2 -c busybox2 -- /bin/sh 
/ # ls /opt/
/ # 

数据卷挂载：一个容器多路径

apiVersion: v1
kind: Pod
metadata:
  name: nfs-pod5
spec:
  containers:
  - image: busybox:1.0
    imagePullPolicy: IfNotPresent
    name: busybox1
    command:
      - "/bin/sh"
    args:
      - "-c"
      - "sleep 36000"
    volumeMounts:
    - mountPath: /home
      name: example-volume3
    - mountPath: /opt
      name: example-volume3
  volumes:
  - name: example-volume3
    persistentVolumeClaim:
      claimName: nfs-pvc5

Pod中只有一个容器，外挂目录分别是/opt与/home,进入容器，在/opt目录下创建bbb文件，由于没有subPath参数，文件创建在存储卷的根目录，所以/home目录下也会产生bbb文件

[root@master subpath]# kubectl apply -f nfs-pod5.yaml
[root@master subpath]# kubectl exec -it nfs-pod5 -- /bin/sh
/ # touch /opt/bbb
/ # ls /home/
bbb

服务端存储卷

[root@localhost default-nfs-pvc5-pvc-4af7377e-5941-4e49-8846-d5f983a8139b]# ls
bbb

加上subPath参数后

apiVersion: v1
kind: Pod
metadata:
  name: nfs-pod6
spec:
  containers:
  - image: busybox:1.0
    imagePullPolicy: IfNotPresent
    name: busybox1
    command:
      - "/bin/sh"
    args:
      - "-c"
      - "sleep 36000"
    volumeMounts:
    - mountPath: /home
      subPath: home
      name: example-volume3
    - mountPath: /opt
      subPath: opt
      name: example-volume3
  volumes:
  - name: example-volume3
    persistentVolumeClaim:
      claimName: nfs-pvc6

Pod中只有一个容器，外挂目录分别是/opt与/home,进入容器，在/opt目录下创建bbbb文件，由于添加subPath参数，文件创建在存储卷的对应的子目录，所以/home目录下不会产生bbb文件

[root@master subpath]# kubectl exec -it nfs-pod6 -- /bin/sh
/ # touch /opt/bbbb
/ # ls /home/
/ #

服务端存储卷

[root@localhost default-nfs-pvc6-pvc-35e5e4ad-c30c-4a93-8650-0573d6f0d11d]# ls
home  opt

配置项configMap/Secret

不加subPath参数，容器中挂载的目录文件都会被覆盖

tomcatconfigmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: tomcat-config
  labels:
    app: tomcat-config
data:
  test1.xml: |
    test1
  test2.xml: |
    test2

tomcat-pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: tomcatpod
spec:
  containers:
  - image: tomcat:1.0
    imagePullPolicy: IfNotPresent
    name: tomcat
    volumeMounts:
    - mountPath: /usr/local/tomcat/temp
      name: tomcat-config
  volumes:
    - name: tomcat-config
      configMap:
        name: tomcat-config

[root@master configmap]# kubectl apply -f tomcatconfigmap.yaml 
configmap/tomcat-config created
[root@master configmap]# kubectl apply -f tomcat-pod.yaml 
pod/tomcatpod created
[root@master configmap]# kubectl exec -it tomcatpod -- /bin/bash
root@tomcatpod:/usr/local/tomcat# cd temp/
root@tomcatpod:/usr/local/tomcat/temp# ls
test1.xml  test2.xml

加上subPath参数，容器中挂载的目录文件就不会被覆盖

tomcat-podsubpath.yaml

apiVersion: v1
kind: Pod
metadata:
  name: tomcatpodsubpath
spec:
  containers:
  - image: tomcat:1.0
    imagePullPolicy: IfNotPresent
    name: tomcat
    volumeMounts:
    - mountPath: /usr/local/tomcat/temp/test3.xml #最终容器中的文件名
      subPath: test1.xml     #configmap中的键。一般来说，名称应该保持一致，这边只是演示
      name: tomcat-config
    - mountPath: /usr/local/tomcat/temp/test2.xml
      subPath: test2.xml
      name: tomcat-config
  volumes:
    - name: tomcat-config
      configMap:
        name: tomcat-config

[root@master configmap]# kubectl apply -f tomcat-podsubpath.yaml
[root@master configmap]# kubectl exec -it tomcatpodsubpath -- /bin/bash
root@tomcatpodsubpath:/usr/local/tomcat# ls temp
safeToDelete.tmp  test2.xml  test3.xml
root@tomcatpodsubpath:/usr/local/tomcat# cat temp/test3.xml 
test1