https://cloud-images.ubuntu.com/releases/16.04/release/ubuntu-16.04-server-cloudimg-amd64-disk1.img
http://download.cirros-cloud.net/0.4.0/cirros-0.4.0-aarch64-disk.img
https://cloud-images.ubuntu.com/releases/14.04/release/ubuntu-14.04-server-cloudimg-arm64-uefi1.img
https://cloud-images.ubuntu.com/releases/16.04/release/ubuntu-16.04-server-cloudimg-amd64-disk1.img
http://download.cirros-cloud.net/0.4.0/cirros-0.4.0-aarch64-disk.img
https://cloud-images.ubuntu.com/releases/14.04/release/ubuntu-14.04-server-cloudimg-arm64-uefi1.img