How the Build Process Works

build.sh iterates through stage directories in alphanumeric order and processes each one.

Stage Processing

For each stage directory:

Skip the stage entirely if a SKIP file is present.
Run prerun.sh — typically copies the rootfs from the previous stage.
Iterate through each numbered subdirectory (e.g. 00-configure-apt, 01-sys-tweaks) in order.
Within each subdirectory, process these files if present:

File	Description
`00-run.sh`	Shell script run on the host (must be executable)
`00-run-chroot.sh`	Shell script run inside the chroot (must be executable)
`00-debconf`	Passed to `debconf-set-selections`
`00-packages`	Packages installed via `apt-get install`
`00-packages-nr`	Same, but with `--no-install-recommends`
`00-packages-<arch>`	Arch-specific packages (e.g. `00-packages-amd64`, `00-packages-arm-only`)
`00-packages-nr-<arch>`	Arch-specific packages without recommends
`00-patches`	Directory of quilt patches applied to the rootfs
`00-patches-<arch>`	Arch-specific quilt patches

If the stage contains EXPORT_IMAGE, EXPORT_ISO, or EXPORT_SQUASHFS (and SKIP_IMAGES is not present), add it to the export queue.

After all stages are processed, the build runs the export pipeline for each queued stage:

Marker file	Export pipeline	Output
`EXPORT_IMAGE`	`export-image/`	`.img` disk image (RPi)
`EXPORT_ISO`	`export-iso/`	`.iso` live image (amd64)
`EXPORT_SQUASHFS`	`export-squashfs/`	`.squashfs` filesystem archive

Multiple marker files can coexist in the same stage — all matching exports will run.

prerun.sh — rsync rootfs into work dir
01-set-sources — clean apt caches, run final upgrade
02-network — configure resolv.conf
03-finalise — rewrite fstab for live use, generate initramfs, build squashfs, build ISO with grub-mkrescue

Scripts and package files support arch suffixes:

Scripts that handle arch themselves check ${ARCH} and exit early if not applicable.