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Linux is a Unix-like and mostly POSIX-compliant computer operating system (OS)

What are the practical differences between Unix and Linux without getting into a flame war, because I'm not asking which one is better, I'm asking about the differences between the two. an objective comparison would be perfect to me. Thank you!

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    I'd agree with the general notion of closing this question, but it seems most people are voting to close because of "opinion-based" which seems objectively incorrect (they even explicitly said they're not asking which one is better). It's a question seeking an objective qualification of the difference. There's no opinion in that. It is far too broad of a statement but I'm afraid if I vote to close for that, it'll close the question for the wrong reason.
    – Bratchley
    May 12, 2016 at 13:22
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    To the asker: the differences are huge and numerous. Modern Unix and Linux are only similar in that there's a core set of functionality that is so old that it was a common inspiration for all the modern iterations. They're also alike in that they're more similar to one another than to something like Windows. That's about as much as I could possibly go into the subject without effectively teaching a college-level course on the subject. If you rephrase the question to be more pointed then it's answerable.
    – Bratchley
    May 12, 2016 at 13:24
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    There are a lot of differences ( one interesting difference is that Linux is free/open-source and most UNIX operating systems are not free , but there are many-many other differences). You could try typing in google "differences between linux and unix" and read the numerous pages it finds, because this topic is just too big
    – mazs
    May 12, 2016 at 13:35
  • @Bratchley seeking an objective qualification of the difference that's my point behind asking this question
    – 0x0584
    May 12, 2016 at 13:35
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    @010010001 unfortunately, it's still too broad. The question as put would be like me asking to describe in what objective ways you are different than one of your parents. It's answerable in a kind of vague way, but would require too much time to answer in any way vaguely approaching complete. By "more pointed" I was meaning more along the lines of asking a specific question so that the answer wouldn't take 50 pages to answer appropriately. I've posted some vague details on the other answer that might give you a vague idea if that's all you're going for but we can't answer a question this broad
    – Bratchley
    May 12, 2016 at 13:43

2 Answers 2

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From a practical POV, the main difference between the terms Unix and Linux is that the former describes a wider family of operating systems, while the latter describes a more specific subgroup.

For all practical purposes (thus ignoring RMS, technical accuracy, trademarks and other legal aspects), the term Linux applies to a number of operating systems, known as distributions: e.g. Red Hat, Fedora, Ubuntu, Debian and so on.

Unix (again, blatantly ignoring technical accuracy, trademarks and other legal aspects) is a wider family of operating systems to which Linux belongs. Thus, we could say that all Linux distributions are part of the Unix family. But people have come to use the term Unix to mean Unix operating systems other than Linux. Examples of Unix that are not Linux include OS X, FreeBSD, and Solaris.

Asking for the differences between Unix and Linux is like asking for the differences between Mammals and Dogs.

All dogs are mammals, but one could say that they are generally more suited for being pets than other mammals. That does not mean that other mammals like cats can't be excellent pets.

In the same way, it would be ok to say that generally speaking Linux is less expensive than Unix (that does not exclude the existence of expensive Linux or free Unix distributions)

If you want to compare one operating system to another you will have too be more specific, cause otherwise the terms are to vague to make a clear comparison.

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    "Unix (again, ignoring technical accuracy, trademarks and other legal aspects) is a wider family of operating systems to which Linux belongs." I'm going to have to disagree with this one. Saying Linux isn't Unix is not some sort of pedantic academic argument, they really are different beasts. "Unix-like" is really the best way to describe it. There's undoubtedly inspiration from Unix, but Linux deviates pretty heavily in a lot of areas. That's especially true if "Unix" is understood to mean the traditional Unix OS's like AIX and Solaris.
    – Bratchley
    May 12, 2016 at 13:28
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    that's why I stated ignoring technical accuracy. The OP is clearly new to Linux and Unix to be asking this, no need to confuse him/her getting into details like that. He asked for practical differences.
    – Sam F
    May 12, 2016 at 13:32
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    And there are huge practical differences. Again it's not an academic point where it requires a detailed understanding of the structure of the OS. There are lots of differences that directly impact your ability the administer the system. Package management, device management, operating system tunables, resource control, and firewalling are a broad set of just a few of the things an admin will need to understand to use the system and they vary wildly even between each other much less between Unix and Linux (for example there's no sysfs in AIX or ODM in Linux).
    – Bratchley
    May 12, 2016 at 13:35
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    I read you but my I think my answer is still appropriate, taking into account the context. Just edited to state that I'm blatantly ignoring technical accuracy...
    – Sam F
    May 12, 2016 at 13:37
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    And what I'm saying is that it's so incorrect there's no way that's a good way to describe it to someone. It doesn't make the subject simpler or easier to understand, it just says a thing that's not accurate.
    – Bratchley
    May 12, 2016 at 13:39
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Unix is the mother OS, invented in the 60s. Over time it changed into a standard or certification. Nowadays Mac OS X is certified as UNIX, to give an example. Linux is not UNIX certified.

The main problem with Unix was that it was very expensive. You needed expensive machinery, an expensive license, and an expensive administrator. We're talking tens of thousands of dollars or euros a year. Not a computer you buy as a student. This still goes for AIX and Solaris, which are mainly used by bigger companies and organizations.

Linux grew out of the wish to have an OS available that was cheap and could run on common hardware, like the average PC. One of the features was to make it "free", with a proper license: GNU. It's freely available, doesn't cost anything to download and install, and can run on a cheap computer. Take a Raspbian PI, $40, and there you go.

Technically Linux is built from the ground up, except there where software providers gave away their code. The older UNIX systems like AIX and Solaris are still available, but I wonder how long it will take before IBM and Oracle think it's cheaper to run everything on Linux.

Using Linux as a user or admin, it's mostly the same. Commands are very similar, but there are differences, just as between AIX and Solaris I guess.

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    "Using Linux as a user or admin, it's mostly the same." I'd have to ask how much Unix you've actually had to deal with. Once you get outside of certain core areas (like command names and their general purposes) the differences are actually pretty big and easily noticeable without delving into the details of the OS.
    – Bratchley
    May 12, 2016 at 13:46
  • I haven't worked with UNIX much, well except then for Mac OS X, which I don't consider a "real" UNIX like AIX. But even that OS is pretty different from Linux, so there you go.
    – SPRBRN
    May 12, 2016 at 14:34

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