Not really. The roots of OS X/MacOS are in NeXTSTEP. It uses a Mach microkernel that originated at CMU, as opposed to the FreeBSD kernel (or anything like it, really).

That said, a bunch of FreeBSD userland code and utilities were ported over to make the OS POSIX-ish.

It's probably easiest to think of a Mac as an amalgam of many different influences and operating behaviors, as opposed to a direct descendant of any one particular lineage.

The Darwin kernel in OSX has more than userland code taken from FreeBSD. "The kernel of Darwin is XNU, a hybrid kernel which uses OSFMK (Open Software Foundation Mach Kernel) from the OSF, various elements of FreeBSD (including the process model, network stack, and virtual file system)" [0]

[0] https://en.wikipedia.org/wiki/Darwin_%28operating_system%29

That was more true in the past.

https://www.amazon.com/Mac-OS-Internals-Approach-paperback/d...

https://www.amazon.com/Mac-OS-iOS-Internals-Apples/dp/111805...

Could you explain this in more detail? It seems that the network stack, VFS, etc. from BSD are still heavily used?

https://github.com/apple/darwin-xnu/tree/master/bsd

Also, more recently they imported pf from OpenBSD:

https://github.com/apple/darwin-xnu/blob/master/bsd/net/pf.c

Or do you mean that they have recently taken more code from other BSDs than FreeBSD?

I mean that they have been moving away into more macOS specific code.

The POSIX network stack for example, is now deprecated, and one must use Network.framework for the more up to date features,

"Introducing Network.framework: A modern alternative to Sockets"

https://developer.apple.com/videos/play/wwdc2018/715/

"Optimizing Your App for Today’s Internet"

https://developer.apple.com/videos/play/wwdc2018/714/

Likewise the long term roadmap introduced in Catalina plans to turn macOS into a micro-kernel, by moving all kernel extensions into userspace drivers.

This is about right, and it's changed to be more this way over time. Early versions of OS X had user lands which were more BSD-like than they are now (and optional! Used to be you had to install the "BSD Subsystem" package from your install CD if you wanted to get a proper POSIX environment). For instance, early versions used BSD init, but that was replaced with launchd.

Early versions of OS X had user lands which were more BSD-like than they are now

They still have a lot of userland BSD parts. Including the very broken grep from FreeBSD (which is fixed in FreeBSD now IIRC):

    $ echo "abcdef" | /usr/bin/grep -o "^..."
    abc
    def

(I have to use the full path to grep, because I replace macOS grep by GNU grep.)

People really should complain to Apple about this.

* https://unix.stackexchange.com/a/398249/5132

> It uses a Mach microkernel that originated at CMU,

The macOS kernel is derived from what Apple chooses to release as XNU, which is Mach-ish.

DarwinBSD was/is the base of MacOS but many will argue that it is its own `thing` now.

Darwin is just a name for macOS / OSX. They're the same thing.

There may be confusion due to the fact that Apple used to publish a Darwin iso that you could boot on their ppc machines, but that's been a long time and OSX is still Darwin. If you run uname on a mac it will tell you that it's Darwin.

this is a common misconception. no, it's not.