Code review comment for ~jibel/curtin/+git/add-layer-images-support:master

To illustrate this feature and for the sack of completeness, here is an example:

Curtin configuration file:

=====
showtrace: true
storage:
    version: 1
    config:
      - id: vda
        type: disk
        ptable: msdos
        path: /dev/vda
        wipe: superblock
        grub_device: true
      - id: vda1
        type: partition
        number: 1
        size: 10GB
        device: vda
        flag: boot
      - id: vda1_root
        type: format
        fstype: ext4
        volume: vda1
        label: 'desktop-rootfs'
      - id: vda1_mount
        type: mount
        path: /
        device: vda1_root
sources:
  - fsimage-layered://cdrom/casper/02-install/desktop-fr.squashfs
=====

Install a desktop from this configuration with this command:

$ sudo curtin -vv -c config.yaml install

Installation logs: http://paste.ubuntu.com/p/bFbrXbP7CQ/

The Desktop image used for this test is to big for my bandwidth to upload it somewhere but we can do a hangout if you want a live demo.