This page describes the minimal components needed for a minimal PureDarwin system (also known as "PureDarwin nano").
This system is a proof-of-concept of a minimal bootable Darwin 9 system that can be built from the components that Apple provides through the DarwinBuild project.
A ready-made VMware virtual machine containing a minimal Darwin 9 system (PureDarwin nano (based on 9C31)) can be downloaded here.
MD5 (puredarwinnano0df46.tbz2) = f6853449e263dd83bba0ac9662f29143
SHA1 (puredarwinnano0df46.tbz2) = 7a32331fcb443538f0737c172160f3cef6067ec9
The virtual machine contains an ISO that could be used on real hardware as well.
Here is what such a minimal system needs to consist of:
Notes: VoodooPS2* or (exclusively) ACPIPS2Nub.kext and ApplePS2Controller.kext (sources) are only required if you want to use a PS/2 keyboard and/or mouse.
The number of files can be further brought down by using a prelinked mach_kernel. This removes the need for the System directory.
Using kextcache, the boot process can be faster, the image bigger.
Chameleon is reported to work.
An installer is currently being prepared.
An interactive shell is run by default. In fact, /sbin/launchd is replaced by a shell script that runs /bin/bash
The Z shell (zsh) is also usable as an interactive UNIX command interpreter (shell).