I'm trying to boot an instance from a volume using a HOT template. Unfortunately the creation of the instance fails (I just get a very generic "Error" as message) while the volume creation works. If I create an instance from an image things work as they should. As I only have access via Horizon I fear that my debugging capabilities are quite limited.

Here's my template (I use hardcoded parameters for testing)

heat_template_version: 2013-05-23

description: boot instance from volume


resources:
  my_instance:
    type: OS::Nova::Server
    depends_on: cinder_volume
    properties:
      key_name: my_key
      flavor: c1.micro
      name: test
      networks: [{"network": "private"}]
      block_device_mapping: [{ device_name: "vda", volume_id : { get_resource : cinder_volume }, delete_on_termination : "true" }]


  cinder_volume:
    type: OS::Cinder::Volume
    properties:
      size: 10
      image: "Ubuntu Trusty 14.04"

This question has been asked before, but I didn't find any solution.