* If the size of the initrd is too large, it cannot properly unpack into vm's RAM --- size of RAM must be increased accordingly. We could also change [boot params](https://www.lightofdawn.org/blog/?viewDetailed=00128), or use shared disks, etc.

* For hyperkit, apple's vmnet requires sudo to create a bridge interface on host. We've played with a version that use's vpnkit and port forwarding (like linuxkit/Docker for Mac), but this adds lots of complexity in image, and opted for the simpler approach.

* We would like a better template mechanism for reusing base images and extending. Right now, we support using base image reuse, with extensions through docker buildargs---ideally, we would want something like %include support in Dockerfiles.

* Finally, we're investigating how to make images work well on multiple providers. For example, ubuntu does not play nice with hyperkit out-of-the-box, but works fine for vbox and kvm.