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Ask HN: Why is Mac OS X/iOS not called a flavor of Unix?

7 points by ForFreedom 11y ago

OSX and iOS are built on linux why aren't they called flavor of linux?

ben_bai 11y ago
Depends on what you mean by Unix. But OS X is UNIX. www.opengroup.org/openbrand/register/brand3602.htm
- RexRollman 11y ago
  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%25252F9.html http://www.opengroup.org/csq/repository/RID=apple%25252FXY1%...
  - ben_bai 11y ago
    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.
deleted 11y ago
[deleted]
detaro 11y ago
Because it is wrong, they are not build on Linux. The roots go back to a BSD, so it's a Unix.
- ForFreedom 11y ago
  Yes, correct... There are falv of Unix too - http://www.linfo.org/flavors.html http://www.linfo.org/flavors.html
  - karlshea 11y ago
    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 11y ago
      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 11y ago
        > Linux is not an ancestor of any flavor of Unix. I don't think I suggested that it was.
unimpressive 11y ago
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 11y ago
  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
misterdata 11y ago
OS X is built around the XNU kernel. XNU stands for "X is Not UNIX" so that's a clue :-)
informatimago 11y ago
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.
deleted 11y ago
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jamer 11y ago
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

7 points by ForFreedom 11y ago

OSX and iOS are built on linux why aren't they called flavor of linux?

ben_bai 11y ago

Depends on what you mean by Unix. But OS X is UNIX. www.opengroup.org/openbrand/register/brand3602.htm

RexRollman 11y ago
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%25252F9.html http://www.opengroup.org/csq/repository/RID=apple%25252FXY1%...
- ben_bai 11y ago
  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.

deleted 11y ago

[deleted]

detaro 11y ago

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

ForFreedom 11y ago
Yes, correct... There are falv of Unix too - http://www.linfo.org/flavors.html http://www.linfo.org/flavors.html
- karlshea 11y ago
  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 11y ago
    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 11y ago
      > Linux is not an ancestor of any flavor of Unix. I don't think I suggested that it was.

unimpressive 11y ago

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 11y ago
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

misterdata 11y ago

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

informatimago 11y ago

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.

deleted 11y ago

[deleted]

jamer 11y ago

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