I have run into a Kubernetes related issue. I just moved from a Pod configuration to a ReplicationController for a Ruby on Rails app and I'm using persistent disks for the Rails pod. When I try apply the ReplicationController it gives the following error:

The ReplicationController "cartelhouse-ror" is invalid. spec.template.spec.volumes[0].gcePersistentDisk.readOnly: Invalid value: false: must be true for replicated pods > 1; GCE PD can only be mounted on multiple machines if it is read-only

Does this mean there is no way to use persistent disks (R/W) when using ReplicationControllers or is there another way?

If not, how can I scale and/or apply rolling updates to the Pod configuration?

Pod configuration:

apiVersion: v1
kind: Pod
metadata:
  name: appname
  labels:
    name: appname
spec:
  containers:
        - image: gcr.io/proj/appname:tag
      name: appname
      env:
            - name: POSTGRES_PASSWORD
              # Change this - must match postgres.yaml password.
          value: pazzzzwd
            - name: POSTGRES_USER
          value: rails
      ports:
            - containerPort: 80
          name: appname
      volumeMounts:
              # Name must match the volume name below.
            - name: appname-disk-per-sto
              # Mount path within the container.
          mountPath: /var/www/html
  volumes:
        - name: appname-disk-per-sto
      gcePersistentDisk:
            # This GCE persistent disk must already exist.
        pdName: appname-disk-per-sto
        fsType: ext4

ReplicationController configuration:

apiVersion: v1
kind: ReplicationController
metadata:
      labels:
        name: appname
      name: appname
spec:
      replicas: 2
      selector:
        name: appname
      template:
        metadata:
          labels:
            name: appname
        spec:
          containers:
            - image: gcr.io/proj/app:tag
              name: appname
              env:
                - name: POSTGRES_PASSWORD
                  # Change this - must match postgres.yaml password.
                  value: pazzzzwd
                - name: POSTGRES_USER
                  value: rails
              ports:
                - containerPort: 80
                  name: appname
              volumeMounts:
                  # Name must match the volume name below.
                - name: appname-disk-per-sto
                  # Mount path within the container.
                  mountPath: /var/www/html
          volumes:
            - name: appname-disk-per-sto
              gcePersistentDisk:
                # This GCE persistent disk must already exist.
                pdName: appname-disk-per-sto
                fsType: ext4