kubernetes之subpath的使用

一.subpath简单说明

在Pod中共享卷以供多方使用是很有用的。VolumeMounts.subPath属性可用于指定所引用的卷内的子路径，而不是其根路径。

二.subpath使用场景

1个Pod中可以有多个容器，这里将不同容器的路径挂载在存储卷volume的子路径，这种场景需要使用到subpath。
volume支持将configMap/secret挂载到容器的路径，但是会覆盖容器路径下原有的文件。如何支持选定configmap/secret的key-value挂载到容器中，且不会覆盖掉原目录下的文件，这个时候可以用subpath。

2.1 存储卷挂载

# 这里我们提前创建好一个PVC-CLAIM名称为pvc-subpath
[root@k8s001 subpath]# cat pvc.yaml 
---
kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv-subpath
  labels:
    release: stable
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Recycle
  hostPath:
    path: /mnt/yuhaohao             # 这个是宿主机真实存在的目录
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-subpath
  namespace: default
spec:
 accessModes: ["ReadWriteOnce"]
 resources:
   requests: 
     storage: 10Gi
[root@k8s001 subpath]# kubectl apply -f pvc.yaml 
[root@k8s001 ~]# cat subpath.yaml
[root@k8s001 subpath]# cat subpath.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-subpath-yuhaohao
spec:
  containers:
  - name: redis-container
    image: redis
    volumeMounts:
    - mountPath: /var/lib/redis             # 容器1的挂载目录
      name: subpath-volume                  # 这里指定pvc的volume名称
      subPath: redispvc                     # 存储卷pvc-subpath要挂载的/mnt/yuhaohao的子目录
  - name: nginx-container
    image: nginx
    volumeMounts:
    - mountPath: /var/www/nginx             # 容器2的挂载目录
      name: subpath-volume                  # 这里指定pvc的volume名称
      subPath: nginxpvc                     # 存储卷pvc-subpath要挂载的/mnt/yuhaohao的子目录
  volumes:
  - name: subpath-volume
    persistentVolumeClaim:
      claimName: pvc-subpath                # PVC的名字
[root@k8s-master zhanglei]# kubectl create -f subpath.yaml
[root@k8s001 subpath]# kubectl get pod 
NAME                   READY   STATUS    RESTARTS   AGE
pod-subpath-yuhaohao   2/2     Running   0          106s
[root@k8s001 yuhaohao]# pwd
/mnt/yuhaohao
[root@k8s001 yuhaohao]# ls
nginxpvc  redispvc

2.2 configmap挂载

2.2.1 创建configmap

[root@k8s001 subpath]# cat configmap.yaml 
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: configmap-subpath
  namespace: default
data:
  example.property.1: hello      # key-value键值对
  example.property.2: world
  example.property.file: |-
    property.1=value-1
    property.2=value-2
    property.3=value-3
[root@k8s001 subpath]# kubectl apply -f configmap.yaml 
configmap/configmap-subpath created
[root@k8s001 subpath]# kubectl get cm
NAME                DATA   AGE
configmap-subpath   3      35s
[root@k8s001 subpath]# cat pod-configmap.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: configmap-subpath-test
  labels:
    purpose: configmap-subpath-test
spec:
  containers:
  - name: configmap-subpath-test 
    image: nginx
    volumeMounts:
      - name: config-volume
        mountPath: /etc/nginx/example.property.1       # 容器挂载的目录路径为容器的/etc/nginx，文件名为example.property.1
        subPath: example.property.1                    # 将key名称作为文件名，hello作为文件内容
  volumes:
  - name: config-volume
    configMap:
      name: configmap-subpath      # 指定使用哪个CM
[root@k8s001 subpath]# kubectl apply -f pod-configmap.yaml 
pod/configmap-subpath-test created
[root@k8s001 subpath]# kubectl get pod 
NAME                     READY   STATUS    RESTARTS   AGE
configmap-subpath-test   1/1     Running   0          7s
[root@k8s001 subpath]# kubectl exec configmap-subpath-test cat /etc/nginx/example.property.1
hello