Build system image(TODO: package system+vendor by default and put onto /system) The recommendation is to use another layer of chroot with the Ubuntu image to build the system image.
Run dhd helpers:
All the rpm files are built using sb2 and mb2. sb2 is a qemu program that runs commands and installs packages in the $DEVICE target chroot.
Most packages are already pre-built and fetched from the Jolla repos. (Also Silica and other stuff which is closed source)
Configs are set up, libs and bins copied, users/groups set up
Then mic is run: Creates a filesystem image, mounts it, then installs everything from the $DEVICE target and all packages you have marked for inclusion into the final image. During installation, oneshot programs fire, demo content is downloaded, more stuff is set up, install scripts do their thing.
The end result is a packaged .zip file with the boot image, the sailfish rootfs image and flashing scripts.