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

The answer is - for now - you can't. Here's a couple of discussion threads from the Kubernetes issues:

• https://github.com/GoogleCloudPlatform/kubernetes/issues/6120
• https://github.com/GoogleCloudPlatform/kubernetes/issues/831

However, may I suggest that you have an alternate design that might work better?

1. If your assets are locked at the point of the container going live, you could use something like gitRepo volume which would copy it to an emptyDir at the point of going live, and would mean you wouldn't have to move the content around at all, just download it directly to the shared directory.
2. If your assets are locked at the point of the container being built, it's probably best to copy them in at that point, using the Docker COPY command.
3. If you really want to stick with the way you're doing it, you would have to copy the content to the emptyDir volume, which is designed for exactly what you're looking for (minus the lack of having to copy it in).

NFS[1] volumes also could solve your problem, but may be overly complex.

Additionally, I'd recommend that these two services exist in different pods, so you can scale each separately. You can create a service endpoint to communicate between them if you need to.

[1] https://github.com/GoogleCloudPlatform/kubernetes/blob/master/examples/nfs/nfs-web-pod.yaml

[update-2016-8] In latest Kubernetes release, you can use a very nice feature named init-container to replace the postStart part in my answer below, which will make sure the container order.

apiVersion: v1
kind: Pod
metadata:
  name: javaweb-2
spec:
  initContainers:
  - name: war
    image: resouer/sample:v2
    command: ["cp", "/sample.war", "/app"]
    volumeMounts:
    - mountPath: /app
      name: app-volume
  containers:
  - name: tomcat
    image: resouer/mytomcat:7.0
    command: ["sh","-c","/root/apache-tomcat-7.0.42-v2/bin/start.sh"]
    volumeMounts:
    - mountPath: /root/apache-tomcat-7.0.42-v2/webapps
      name: app-volume
    ports:
    - containerPort: 8080
      hostPort: 8001
  volumes:
  - name: app-volume
    emptyDir: {}

NOTE: initContainer is still a beta feature so the work version of this yaml is actually like: http://kubernetes.io/docs/user-guide/production-pods/#handling-initialization, please notice the pod.beta.kubernetes.io/init-containers part.

---original answer begin---

Actually, you can. You need to use container life cycle handler to control what files/dirs you want to share with other containers. Like:

---
apiVersion: v1
kind: Pod
metadata:
    name: server
spec:
    restartPolicy: OnFailure
    containers:
    - image: resouer/sample:v2
      name: war
      lifecycle:
        postStart:
          exec:
            command:
              - "cp"
              - "/sample.war"
              - "/app"
      volumeMounts:
      - mountPath: /app
        name: hostv1 
    - name: peer
      image: busybox
      command: ["tail", "-f", "/dev/null"]
      volumeMounts:
      - name: hostv2
        mountPath: /app/sample.war
    volumes:
    - name: hostv1
      hostPath:
          path: /tmp
    - name: hostv2
      hostPath:
          path: /tmp/sample.war

Please check my gist for more details:

https://gist.github.com/resouer/378bcdaef1d9601ed6aa

And of course you can use emptyDir. Thus, war container can share its /sample.war to peer container without mess peer's /app directory.

If we can tolerate /app been overridden, it will be much simpler:

---
apiVersion: v1
kind: Pod
metadata:
  name: javaweb-2
spec:
  restartPolicy: OnFailure
  containers:
  - image: resouer/sample:v2
    name: war
    lifecycle:
      postStart:
        exec:
          command:
            - "cp"
            - "/sample.war"
            - "/app"
    volumeMounts:
    - mountPath: /app
      name: app-volume
  - image: resouer/mytomcat:7.0
    name: tomcat
    command: ["sh","-c","/root/apache-tomcat-7.0.42-v2/bin/start.sh"]
    volumeMounts:
    - mountPath: /root/apache-tomcat-7.0.42-v2/webapps
      name: app-volume
    ports:
    - containerPort: 8080
      hostPort: 8001 
  volumes:
  - name: app-volume
    emptyDir: {}