Re-tested:

= amd64 =

$ sudo ubuntu-device-flash --verbose core --size 3 --channel edge --output=amd64.img --device-part device-e4e9d6632c5266aac95bde68729bcce796509f6abeac8c7ebca25be34aa0c431.tar.xz --oem ./generic-amd64.canonical_1.
0_all.snap 15.04
Determining oem configuration
Fetching information from server...
Downloading and setting up...
Using a custom device tarball
Searching for hardware.yaml in device part
Download finished for /home/james/device-e4e9d6632c5266aac95bde68729bcce796509f6abeac8c7ebca25be34aa0c431.tar.xz
Partitioning...
Download finished for /home/james/.cache/ubuntuimages/ubuntu-core/15.04/edge/generic_amd64/version-26.tar.xz
Download finished for /home/james/.cache/ubuntuimages/pool/ubuntu-4fbe24300a5d5e443a0a455fc3428f780d273bd03673896cfcf51ba0eba4000d.tar.xz
Mapping...
Formatting...
Mapping...
Mounting...
Provisioning...
Installing ./generic-amd64.canonical_1.0_all.snap
Unmounting...
Unmapping...
New image complete
Summary:
 Output: amd64.img
 Architecture: amd64
 Channel: edge
 Version: 26
Launch by running: kvm -m 768 amd64.img
$ sudo kpartx -avs amd64.img
$ sudo mount /dev/mapper/loop0p2 /mnt
$ cat /mnt/install.yaml 
meta:
  timestamp: 2015-04-22T09:08:41.393114048+01:00
  initial-version: "26"
  system-image-server: https://system-image.ubuntu.com
tool:
  name: ubuntu-device-flash
  path: /usr/bin/ubuntu-device-flash
  version: ""
options:
  size: 3
  size-unit: GB
  output: amd64.img
  channel: edge
  device-part: device-e4e9d6632c5266aac95bde68729bcce796509f6abeac8c7ebca25be34aa0c431.tar.xz
  oem: ./generic-amd64.canonical_1.0_all.snap


= armhf =

$ sudo ubuntu-device-flash --verbose core --size 3 --channel edge --output=armhf.img --device-part device-e4e9d6632c5266aac95bde68729bcce796509f6abeac8c7ebca25be34aa0c431.tar.xz --device generic_armhf 15.04 --oem ./beagleblack.canonical_1.7_all.snap
Determining oem configuration
Fetching information from server...
WARNING: this option should only be used to build azure images
Downloading and setting up...
Using a custom device tarball
Searching for hardware.yaml in device part
Download finished for /home/james/device-e4e9d6632c5266aac95bde68729bcce796509f6abeac8c7ebca25be34aa0c431.tar.xz
Download finished for /home/james/.cache/ubuntuimages/ubuntu-core/15.04/edge/generic_armhf/version-22.tar.xz
Download finished for /home/james/.cache/ubuntuimages/pool/ubuntu-3599d2c285a4bd0f54d0b13a290c4f9c8b10ae10354afee55237994af7a28f1c.tar.xz
Partitioning...
Mapping...
Formatting...
Mapping...
Mounting...
Provisioning...
Installing ./beagleblack.canonical_1.7_all.snap
Replicating system-a into system-b
Unmounting...
Unmapping...
New image complete
Summary:
 Output: armhf.img
 Architecture: armhf
 Channel: edge
 Version: 22
$ sudo kpartx -avs armhf.img
$ sudo mount /dev/mapper/loop0p2 /mnt
$ cat /mnt/install.yaml
meta:
  timestamp: 2015-04-22T09:22:29.418832806+01:00
  initial-version: "22"
  system-image-server: https://system-image.ubuntu.com
tool:
  name: ubuntu-device-flash
  path: /usr/bin/ubuntu-device-flash
  version: ""
options:
  size: 3
  size-unit: GB
  output: armhf.img
  channel: edge
  device-part: device-e4e9d6632c5266aac95bde68729bcce796509f6abeac8c7ebca25be34aa0c431.tar.xz
  oem: ./beagleblack.canonical_1.7_all.snap