I've done the following so far
since I'm considering very minimal installation suitable for appliance, I considered fedora's busybox, but in that case I would need to create a statically linked ostree
as I mentioned I'm not doing this to be for production server nor a workstation
I tried to start with alpine linux, but they don't provide qcow2 images,
so I run
docker run --rm -ti --name a1 -v `pwd`/alpine-root:/data/ alpine /bin/sh
and inside the container I run
the end result was
OK: 120 MiB in 67 packages
compared to 6 MB without ostree and kernel
I guess linux-virtgrsec is the smallest kernel they have
I'm not sure if 120MB for an embedded appliance is good or bad.
and this image does not have a bootloader yet
but ostree seems to be working!
now I have a directory /alpine-root having a working ostree and a kernel
what's next? add a bootloader and make that a qcow2 and make an ostree out of it