// to be owned by the pod:
  //
  // 1. The owning GID will be the FSGroup
  // 2. The setgid bit is set (new files created in the volume will be owned by FSGroup)
  // 3. The permission bits are OR'd with rw-rw----
  //
  // If unset, the Kubelet will not modify the ownership and permissions of any volume.
  // Note that this field cannot be set when spec.os.name is windows.
  // +optional
  optional int64 fsGroup = 5;