
Ask HN: Why is Mac OS X/iOS not called a flavor of Unix? - ForFreedom
OSX and iOS are built on linux why aren&#x27;t they called flavor of linux?
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ben_bai
Depends on what you mean by Unix.

But OS X is UNIX. www.opengroup.org/openbrand/register/brand3602.htm

~~~
RexRollman
Thank you. I don't understand why this is even being debated.

Conformance statement for El Capitan:
[http://www.opengroup.org/csq/repository/RID=apple%25252FXY1%...](http://www.opengroup.org/csq/repository/RID=apple%25252FXY1%25252F9.html)

~~~
ben_bai
It is what it is, trying to define it makes for a good bonfire story but
that's about it.

Today there are only "Unix-like" and UNIX certified systems left. And I bet it
wouldn't be too hard to certify MS Windows with SFU installed, as a UNIX.

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unimpressive
Because they're not.

"OS X's core is a POSIX compliant operating system (OS) built on top of the
XNU kernel, with standard Unix facilities available from the command line
interface. Apple has released this family of software as a free and open
source operating system named Darwin. On top of Darwin, Apple layered a number
of components, including the Aqua interface and the Finder, to complete the
GUI-based operating system which is OS X.[32]" \- "OS X", _Wikipedia, the free
encyclopedia_

[https://en.wikipedia.org/wiki/Mac_OS_X](https://en.wikipedia.org/wiki/Mac_OS_X)

~~~
beckler
Even though OS X isn't pure UNIX, it is UNIX certified.

[http://www.opengroup.org/openbrand/register/brand3612.htm](http://www.opengroup.org/openbrand/register/brand3612.htm)

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detaro
Because it is wrong, they are not build on Linux. The roots go back to a BSD,
so it's a Unix.

~~~
ForFreedom
Yes, correct... There are falv of Unix too -
[http://www.linfo.org/flavors.html](http://www.linfo.org/flavors.html)

~~~
karlshea
Right, it is considered to be a flavor of Unix. But OS X has nothing to do
with Linux other than a common ancestor.

~~~
runjake
Linux is not an ancestor of any flavor of Unix. It did not evolve from a Unix
codebase.

It is the epitome of a "Unix-like" operating system. At an early point, it
might've been fair to call it a _spiritual_ successor of Minix, though.

~~~
karlshea
> Linux is not an ancestor of any flavor of Unix.

I don't think I suggested that it was.

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informatimago
Why is Mac OS X/iOS not called a flavor of Unix?

Because for a time, Unix was a trademark, therefore everybody else didn't have
a unix offereing, but a Solaris, a A/UX, a A/IX, a Xenix, a FreeBSD, an
OpenBSD, a Darwin, a GNU/Hurd, a GNU/Linux, etc.

OSX and iOS are built on linux

No. They're built on Darwin/Mach.

Why aren't they called flavor of linux?

Because they have not a single bit in common with Linux.

------
jamer
TL;DR: OS X is a Unix, while iOS is merely Unix-like but cannot, due to legal
reasons, be called a Unix. Neither are based on Linux, which is itself another
Unix-like but not a Unix.

Unix is a complicated concept and it has embodied different things in the past
decades. It started out simply enough as a single body of code (with various
additional patches made by different groups using it) and a trademark on the
name at AT&T in the '70s. AT&T partnered with various educational institutions
to help explore the concepts in Unix. The most important of these educational
institutions was University of California, Berkeley which created its own
patches for Unix and called them BSD ("Berkeley Software Distribution"). In
the early '80s, AT&T decided it could make money by licensing the code out to
commercial third parties, giving sale and binary redistribution rights. The
many licensees (major ones were IBM, HP, Sun, and Microsoft) added additional
code to their versions of Unix, much of which implemented similar features but
which were all slightly incompatible with each other. In order to reign in the
incompatibilities, various standards were created, such as the various
versions of POSIX, and a Unix vendor could pay to be certified as meeting one
of these standards. In the early '90s, AT&T sued Berkeley so Berkeley decided
to rewrite all the copyrighted parts of BSD with freely-licensed
reimplementations. Later in the '90s, AT&T sold the rights to the Unix
intellectual property to Novell, who eventually transferred it to X/Open
Consortium, who later merged with OSF and ultimately became the Open Group,
where it remains today[1].

GNU/Linux is an operating system created in the early '90s that was heavily
inspired by Unix (we say it is "Unix-like"), but which does not use any
copyrighted Unix code and which is not certified as meeting any of the Unix
compatibility standards. Due to its free nature, a belief that it was "good
enough" for various commercial purposes, and its avoidance of violating the
Unix copyright, it became a nice alternative to the licensed Unixes in the
'90s, since many of those cost money, or were then in legally ambiguous
situations.[2] The Linux kernel itself has continued to grow over the years
and is now used for various operating systems beyond just GNU/Linux, the
biggest of which is probably Android. As far as I know, none of the Linux-
based operating systems today are certified by the Open Group.

Meanwhile, Mac OS X is based partially on BSD, which was not considered an
official Unix, especially after AT&T's lawsuit. At some point, Apple decided
to pursue Mac OS X compliance with the Open Group's UNIX 03 standard, which
just required meeting a lot of technical requirements, and first got it with
Mac OS X 10.5 Leopard. This makes Mac OS X an official Unix. El Capitan
retains the UNIX 03 certification.[3] Since iOS, watchOS, and tvOS are based
on Mac, they are Unix-like. But they're missing a lot of the requirements from
any of the official Unix standards and so cannot be legally called Unixes.

Also, since none of Apple's operating systems use the Linux kernel it would be
incorrect to say they were a flavor of Linux.

Hope this helps!

[1]
[https://en.wikipedia.org/wiki/History_of_Unix](https://en.wikipedia.org/wiki/History_of_Unix)

[2] "Just for Fun" by Linus Torvalds.
[http://www.amazon.com/dp/0066620732](http://www.amazon.com/dp/0066620732)

[3]
[http://www.opengroup.org/openbrand/register/brand3612.htm](http://www.opengroup.org/openbrand/register/brand3612.htm)

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misterdata
OS X is built around the XNU kernel. XNU stands for "X is Not UNIX" so that's
a clue :-)

