So before building each package the board PXE boots and installs the OS onto the USB-attached hard drive? That seems inefficient. Why not use an overlay filesystem and just throw away the changes after each build? Is there even a need for local storage, or could the nodes run off an NFS export?
For one thing each package needs a different build environment, so the overlay filesystem wouldn't necessarily help much. For another, can you say with confidence that the build process (which typically runs some steps as root) will not affect any system state outside of the filesystem?
