Example UEC Build with QEMU image file support in Packer

httpdir_latest_meta-data_index.html

instance-id

httpdir_latest_meta-dir_instance

foo

httpdir_latest_user-data

#cloud-config

ssh_authorized_keys:
  - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDgSCutRwKJRy0fZwx4cFQd3UtmWwg7raFrWKE+o+0la7W0w3kkPApCPvbG3rbfeVYnp8TbOVa2BRpzz+BDxRQ+9xqdbkURlJpB4/5AO3a91QCN4l8NWJdUkqoAKpt4qdSIPU77UnjNH2VRK8ZryKqNTX8vBChOilCTgkQ+qXKjCP2gcOtBS9nL/2R8bCfpm5l9C7HHtoLcb+8OfwrPTodmbv2rXdskk5c5TCCNAOiG0Hv4srSu3awk/rOVJ5itz9BiZN583YSHF2364D2e+h2TFNVeoBhLYdiSPOUcl4ek/Dg1mCkCF+OmZaF81H5EKrAPTAtu+xODOqrJ0TDOpBEx root@test

packer.json

{
  "builders":
  [
    {
      "type": "qemu",
      "output_directory": "output",
      "iso_url": "http://cloud-images.ubuntu.com/trusty/current/trusty-server-cloudimg-amd64-disk1.img",
      "iso_checksum": "350353fbaee61e6b6f8eefa864bc2516",
      "iso_checksum_type": "md5",
      "ssh_wait_timeout": "300s",
      "shutdown_command": "sudo halt -p",
      "disk_size": 5000,
      "format": "qcow2",
      "accelerator": "kvm",
      "disk_image": true,
      "headless": true,
      "http_directory": "httpdir",
      "http_port_min": 80,
      "http_port_max": 80,
      "ssh_host_port_min": 2222,
      "ssh_host_port_max": 2229,
      "ssh_username": "ubuntu",
      "ssh_key_path": "key",
      "ssh_port": 22,
      "vm_name": "uectest",
      "net_device": "virtio-net",
      "disk_interface": "virtio",
      "boot_wait": "5s"
    }
  ]
}

Replace _ with / because gists can't have directories.