Fri Dec 1 15:20:11 EST 2017

buildroot anyway

So pretty much I will need to wrap an RPC call into a Debian

lxc-create can instantiate a VM in about 3 minutes if debs are cached
and the container is created on a ram disk.

lxc-create from cache takes only a couple of seconds.

to wrap this in a nix expression, a tar of the VM should probably be
stored in the nix store as produced by another platform.

Transferring these archives isn't even much of a big deal if they run
in ramdisk on the target host.  So basically:

1. Nix machine calls a "debian factory" to create a VM image, and archives it in its store
2. Nix machine pushes this image to run it under a unique name on an lxc host, and gets a root SSH key
3. Nix machine calls into the VM to create a build product
4. Target VM is removed

All of this doesn't even need nix.  It can be done using just make.
It's the idea.