K8s掛載文件到目錄，不清空原有目錄文件

問題

如果只是使用mount功能來掛載一個文件到某個路徑下，則這個路徑下原有的文件將會被清空。

掛載config.toml到/etc/apt/下

apiVersion: apps/v1
kind: Deployment
    spec:
      volumes:
        - name: runner-config-demo1
          configMap:
            name: runner-config-demo1
            items:
              - key: config.toml
                path: config.toml
      containers:
        - name: lcdp-runner
          image: gitlab-runner:v13.5.0
          volumeMounts:
            - name: runner-config-demo1
              mountPath: /etc/apt/

掛載前

$ ls /etc/apt/
apt.conf.d  auth.conf.d  preferences.d  sources.list  sources.list.d  trusted.gpg.d

掛載后

$ ls /etc/apt/
config.toml

解決

使用subPath功能即可

apiVersion: apps/v1
kind: Deployment
    spec:
      volumes:
        - name: runner-config-demo1
          configMap:
            name: runner-config-demo1
            items:
              - key: config.toml
                path: config.toml
      containers:
        - name: lcdp-runner
          image: gitlab-runner:v13.5.0
          volumeMounts:
            - name: runner-config-demo1
              # 注意，區別只在此處，另外，mountPath和subPath都要加上config.toml。
              mountPath: /etc/apt/config.toml
              subPath: config.toml

掛載后

$ ls /etc/apt/
apt.conf.d  auth.conf.d  config.toml  preferences.d  sources.list  sources.list.d  trusted.gpg.d

備注

Docker Swarm也有類似的掛載問題，還沒找到解決方案，有大佬知道解決方案的，希望可以不吝賜教，在評論區留下解決方案可否