NextBSD

NextBSD was an operating system initially based on the trunk version of FreeBSD as of August 2015. It was a fork of FreeBSD which implemented new features developed on branches, but not yet implemented in FreeBSD. As of 2019, the website is defunct, with the last commits on GitHub dating to October 2019. The Wayback Machine captures of the website after December 15, 2017 are domain squatter pages, and as of March 17, 2021, the site is redirects to a fake "Apple Support" page.

Features
The basic features of launchd, notifyd, asld, and libdispatch work.

These can be installed by cloning the NextBSD repository from GitHub, building GENERIC or MACHTEST kernels, installing a new world on an existing 10.x or CURRENT system, and then following the instructions in the README.

Launchd will start the initial jobs that are part of the repo now.

Planned Features
The project refers to an installer as the first planned milestone on their website.

Future plans included convert to rc and tying notifyd in to potential consumers.

History
NeXTBSD was announced by Jordan Hubbard and Kip Macy in August 2015 at the Bay Area FreeBSD Users Group (BAFUG).

Relationship to FreeBSD
NeXTBSD is based on the FreeBSD-CURRENT kernel while adding in Mach IPC, Libdispatch, notifyd, asld, launchd, and other components derived from Darwin, Apple's open-source code for macOS.

Basic Architecture

 * FreeBSD-current kernel + Mach IPC
 * Common Object Runtime (create/delete/retain/release)
 * Libdispatch / ASL / Libnotify
 * launchd
 * launchctl
 * json config files
 * legacy rc system
 * cooperating daemons

Tasks
The units of resource ownership; each task consists of a virtual address space, a port right namespace, and one or more threads. (Implemented as an extension to a process.)

Threads
The units of CPU execution within a task. Simple extension to kthreads.

Address space
In conjunction with memory managers, Mach implements the notion of a sparse virtual address space and shared memory. (No modifications)

Memory objects
The internal units of memory management. Memory objects include named entries and regions; they are representations of potentially persistent data that may be mapped into address spaces. (Unsupported)

Ports
Secure, simplex communication channels, accessible only via send and receive capabilities (known as port rights).

IPC
Message queues, remote procedure calls, notifications, semaphores, and lock sets. (Mach semaphores and lock sets are not supported).

Time
Clocks, timers, and waiting - (rudimentary shims).

Standards adherence
Current BSD operating system variants support many of the common IEEE, ANSI, ISO, and POSIX standards, while retaining most of the traditional BSD behavior. Like AT&T Unix, the BSD kernel is monolithic, meaning that device drivers in the kernel run in privileged mode, as part of the core of the operating system.

A selection of significant Unix versions and Unix-like operating systems that descend from BSD includes:
 * FreeBSD, an open source general purpose operating system.
 * NeXT NEXTSTEP and OPENSTEP, based on the Mach kernel and 4BSD; the ancestor of Mac OS X (macOS)
 * Apple Inc.'s Darwin, the core of macOS and iOS; built on the XNU kernel (part Mach, part FreeBSD, part Apple-derived code) and a userland much of which comes from FreeBSD