docker - How to mimic '--volumes-from' in Kubernetes

Question

I'm looking for a pattern that allows to share volumes between two containers running on the same pod in Kubernetes.

My use case is: I have a Ruby on Rails application running inside a docker container. The docker image contains static assets in /app/<app-name>/public directory, and I need to access those assets from the nginx container running alongside in the same pod.

In 'vanilla' docker I would have used --volumes-from flag to share this directory:

docker run --name app -v /app/<app-dir>/public <app-image>
docker run --volumes-from app nginx

After reading this doc: https://github.com/GoogleCloudPlatform/kubernetes/blob/master/docs/volumes.md I tried this (only relevant entries presented):

spec:
  containers:
    - image: <app-image>
      name: <app-name>
      volumeMounts:
        - mountPath: /app/<app-name>/public
          name: assets
    - image: nginx
      name: nginx
      volumeMounts:
        - mountPath: /var/www/html
          name: assets
          readOnly: true
    volumes:
      - name: assets
        hostPath:
          path: /tmp/assets

But:

• Even though /tmp/assets on the node exists, it's empty
• /app/<app-name>/public inside the app container is also empty

As a workaround I'm gonna try to populate the shared directory when the application container is up (simply cp /app/<app-name>/public/* to shared directory), but I really dislike this idea.

Question: how to mimic --volumes-from in Kubernetes, or if there is no direct counterpart, how can I share files from one container to other running in the same pod ?

apiVersion: v1beta3

Client Version: version.Info{Major:"0", Minor:"17", GitVersion:"v0.17.0", GitCommit:"82f8bdac06ddfacf493a9ed0fedc85f5ea62ebd5", GitTreeState:"clean"}
Server Version: version.Info{Major:"0", Minor:"17", GitVersion:"v0.17.0", GitCommit:"82f8bdac06ddfacf493a9ed0fedc85f5ea62ebd5", GitTreeState:"clean"}

Answer 1

Waitting for answers