Can you explain the evolution hierarchy of operating systems (Linux and Windows) from Unix?
History – Evolution of Operating Systems from Unix
history
Related Solutions
We can distinguish UNIX the trademark from Unix the code-base.
AT&T
Unix was initially developed at Bell Labs, owned by AT&T. This Unix team became AT&T's Unix System Laboratories (USL) and produced Unix System V (Roman numeral for five) or SysV for short. The University of California at Berkeley (UCB) also licenced Unix for academic use, their Computer Systems Research Group (CSRG) later made many important changes and additions (notably TCP/IP) in their Berkeley Software Distribution (BSD) which were later incorporated into many descendants of Unix leading to the BSD vs SysV split. Ultimately a lot of the BSD changes were back-ported into SysV (which we can consider the main "ancestral Unix" code base).
Along the way, many different businesses have licenced this code-base (at various stages in it's development) and used it as the basis of their proprietary Unix operating systems - AIX, HPUX, IRIX, Solaris, Ultrix and dozens of others.
Novell (Attachmate)
USL was purchased by Novell. At this time, the ancestral Unix code was known as Unix system V release 4 - or SVR4 for short. Novell named their product Unixware to complement the name of their legacy network OS Netware. Novell have been Acquired by Attachmate.
The Santa Cruz Operation
Novell eventually sold their Unix business to an old SVR3.2 licensee The Santa Cruz Operation (SCO) whose main business up to that point was selling a product named OpenServer that was based on Unix SVR3.2. Novell (since bought by Attachmate) still own some rights‡ to Unix but do not do any work on the source code.
Caldera / The Sco Group / TSG Group Inc
The Santa Cruz Operation later sold their Unix business to a Linux company Caldera who later renamed themselves to The SCO Group (sometimes referred to as new SCO or SCOG) and who had a disastrous failure of leadership leading to chapter-11 bankruptcy and sale of the Unix business to UnXis, a business formed for this purpose. Subsequently The SCO Group were reorganised into TSG Group Inc and TSG Operations Inc. They have no role regarding maintenance of the ancestral Unix code base. In August 2012 TSG Group Inc converted to chapter 7 bankruptcy.
UnXis / Xinuos
So now UnXis are responsible for marketing and developing/maintaining Unixware - the ancestral AT&T Unix code base. Because the Santa Cruz Operation (old SCO) originally ported† Unix to the x86 platform, I believe x86 and x86_64 are the only target platforms that UnXis directly support.
On June 12 2013, UnXis announced it had been renamed Xinuos.
Xinuos no longer seriously support installation of their ancestral Unix products on bare metal. Their SVR3.2 and SVR5 based products are offered as virtual machines (VM) to be run under their "OpenServer 10" product which is a derivative of FreeBSD.
So the body of code with the greatest claim to be the prime descendant of the ancestral Unix code is now, in practical terms, not much more than a compatibility layer between other operating systems and legacy applications.
† Microsoft licensed Unix and ported it to 16-bit Zilog Z8000 - old SCO purchased Xenix from them and ported it to the 16-bit 8086 architecture (used by IBM for their original IBM PC). Old SCO later ported SVR3.2 to x86 as 32-bit SCO-Unix later renamed OpenServer
‡ Novell's rights were contested, somewhat futilely, by The SCO Group (now named TSG Group Inc), the bankrupt remnants of the old Linux company Caldera. It is not yet clear whether TSG Group Inc have finally discontinued this and related litigation, the last activity in a related case against IBM was January 2018 and TSG Group Inc are not commercially active
It is very tempting to want to define the differences between BSD and Linux. Just like Gilles said in the comments, it is not an easy task since they're so numerous and disparate. Very often, the differences won't even be noticeable at the user's level; everything has been worked out so that the OS behaves as you would expect a Unix to.
Moreover multiple distributions are available for each. No matter what you say about Linux/BSD generally, you'll often find a distribution that contradicts it.
The following is a list of comparisons I found scattered over the web.
- Here on U&L, a user has defined the following differences:
Big differences are (in my opinion of course):
- Userland (Linux uses GNU while BSD uses BSD)
- Integration (Linux is a collection of different efforts, BSD is much more unified at the core)
- Packaging (Linux typically manages installed software in binary packages - BSD typically manages a "ports" tree that you use to build software from sources)
Notice the word typically in his last point. Some Linux distributions will manage source code and conversely some BSDs will manage binary packages.
- Matthew D. Fuller has a lengthy comparison between BSDs and Linux you may want to look into. The article will compare both on Design level, Technical differences, Philosophies and finally address common Myths. Here are some excerpts:
BSD is what you get when a bunch of Unix hackers sit down to try to port a Unix system to the PC. Linux is what you get when a bunch of PC hackers sit down and try to write a Unix system for the PC.
--
BSD is designed. Linux is grown. Perhaps that's the only succinct way to describe it, and possibly the most correct.
- User vivek on FreeBSD forums writes:
Key differences:
- FreeBSD full os. Linux is kernel. Linux distribution is os (100+ majro disrtos).
- FreeBSD everything comes from a single source. Linux is like mix of lot of stuff.
- BSD License vs GPL
- FreeBSD Installer
- BSD commands (ls file -l will not work) vs GPL command (ls file -l will work)
- FreeBSD better and updated man pages.
- BSD rc.d style booting vs Linux SysV style init.d booting
Here are some articles describing the history of each:
Written by Dave Tyson, this article describes the history of many Unix variants (including of course BSD and Linux).
Scott Barman describes how both operating systems came to be and how it forged his opinion:
I will give one "solid" opinion: If I had to choose one system that would act as my router, DNS, ftp server, e-mail gateway, firewall, web server, proxy server, etc., that system would run a BSD-based operating system. If I had to choose one system that would act as my desktop workstation, run X, all the application I like, etc., that system would run Linux. HOWEVER, I would have no problem running Linux as my work horse server or running the BSD-based system on my desktop.
Further reading
- This question here on U&L, compares existing BSDs, highlighting what they have in common.
Best Answer
This is a highly simplified history of Unix and its derivatives. Windows does not figure in it because its history is essentially separate.
Once upon a time operating systems were complex and unwieldy. One day in the late 1960s, Ken Thompson, Dennis Ritchie and a few of their colleagues at AT&T Bell Labs decided to write a simpler version of Multics to run games on their PDP-7, and thus Unix was born.
AT&T held the rights to the code, and licenses were expensive. Many other companies sublicensed Unix and sold their own version. Major players included DEC, HP, IBM, Sun. Unix variants added their own extensions, often nicking ideas from each other and from academia.
Meanwhile, in Berkeley, a number of academics were unhappy with the licensing situation and decided to create a version of Unix that didn't include any AT&T-licensed code. Thus in the early 1980s the Berkeley Software Distribution, or BSD, became a free variant of Unix. BSD first ran on Minicomputers such as PDP-11 and VAXen.
Meanwhile, on the East coast, Richard Stallman threw a fit when he couldn't get the source code to his printer driver. He founded the GNU (GNU's not Unix) project in 1983 intending to make a free Unix-like operating system, only better. After a little hesitation, the kernel of this operating system was chosen to be Hurd, which is going to be usable any decade now. Many components of the GNU project are included in all current free unices, in particular the compiler GCC.
Meanwhile, in Finland, Linus Torvalds went on a hacking binge in summer 1991. When he woke up, he realized that he'd written an operating system for his PC, and he decided to share it by putting it on an FTP server in a directory called linux. The success exceeded his expectations.
Many people created software distributions including the Linux kernel, many GNU programs, the X Window System, and other free software. These distributions (Slackware, Debian, Red Hat, SUSE, Gentoo, Ubuntu, etc.) are what people generally refer to when they say “Linux”. Most Linux distributions consist mostly of free-as-in-speech software, though software that is merely free-as-in-beer is often included when no free equivalent exists.
Other currently existing unices include the various forks of BSD (you get a choice of FreeBSD, NetBSD and OpenBSD, all being free, open and developed through the 'net), as well as a disminishing number of commercial variants targeted towards servers: and AIX, HP-UX, Solaris, and a few very minor contenders. Another proprietary unix-based operating system is Mac OS X running on Apple desktops, laptops and PDAs.