You need and install alpine system on a disk drive with enought disk space, this system is alpine-master
Setup the alpine-master
with doc from https://wiki.alpinelinux.org/wiki/How_to_make_a_custom_ISO_image_with_mkimage
apk add alpine-sdk build-base apk-tools alpine-conf busybox fakeroot syslinux xorriso
adduser build -G abuild
cd /root/
git clone git://git.alpinelinux.org/aports
apk update
Copy the 3 files from builder directory to alpine-master/root/
- build-iso.sh in
/root/
for building an ISO - genapkovl-custom.sh and mkimg.custom.sh in
/root/aports/scripts
Edit build-iso.sh for your needs
The script run-qemu.sh
is an exemple for running a custom ISO with autoconfiguration for network