Setting up the build environment on HDD
In earlier days, Alpine used a separate Gentoo build environment. Nowadays we build in Alpine itself, and things are much simpler.
We will host this build environment on a HDD installed Alpine, using the "edge" repository.
Boot your build environment
Boot the latest Alpine Linux image on a box with a HDD.
Set basic environment settings (when prompted for disk, select the disk(s) that you wish to use, and use them in sys mode. Note that if you specify two disks, soft raid will be setup on them automatically).
Change your repository to use "edge"
Update/upgrade your system
Then reboot your system.
Start building packages
Now you can move on to creating packages for Alpine.