Linux vs Unix: How do they differ?

Determining the differences between Linux and Unix requires a lot of nuance.

While Linux is not Unix, I often find that people wonder what the differences between Linux and Unix are. I’m guilty of that too, as I was unsure of the relationship between the two up until a couple of years ago when I finally sat down and read into it. The short story is that Linux is derived from Unix and is a continuation of Unix design, but in itself is not Unix.



There’s a long and storied history between the two, and it’s extremely difficult to actually find a lot of information on the early days of both systems in context to each other, thanks to many sources being lost to the passage of time. We’ve done the best we can to dig up as much as possible, as nowadays, the differences are surprisingly slim.

Linux vs Unix: Origins

Linux and Unix have an intertwined history, but it’s important to recognize their differences too. Unix was developed as a proprietary operating system in the 1960s by Bell Labs, owned by AT&T. It being proprietary meant that its owners assert control over it in the form of licensing and control of the source code. Nowadays, there are open-source Unix operating systems, such as FreeBSD, but that wasn’t always the case. FreeBSD legally refers to itself as a Unix-like operating system as it has not paid for Unix licensing, but it’s as much Unix as the likes of Solaris are and is often colloquially referred to as Berkeley Unix.

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In the case of Linux, it was built as a hobby project by Linus Torvalds at first. In fact, one of the most famous messages ever in the computing sphere was sent by Torvalds to a Usenet newsgroup on the 25th of August 1991.

Hello everybody out there using minix -I’m doing a (free) operating system (just a hobby, won’t be big and professional like gnu) for 386(486) AT clones. This has been brewing since april, and is starting to get ready. I’d like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).

Linux was inspired by MINIX, a Unix-like kernel written for teaching purposes by Andrew S. Tanenbaum. As Torvalds re-implemented all the MINIX functions into his own kernel (that he dubbed Linux), he chose to build it as a monolithic kernel instead of a microkernel, which Tanenbaum disapproved of.

As an aside, seriously, check that link out. It’s a fascinating read made even more interesting given that we know where Linux is now and where MINIX ended up. Some highlights include Torvalds referring to the “brain-damages” of MINIX, and how he has “more excuses than you have, and Linux still beats the pants of [sic] minix in almost all areas. “

As for Linux itself, it was initially built to run on an Intel 386, a 32-bit microprocessor released in 1985. By this stage, Unix was well-cemented as a known operating system, with many systems making use of it.

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Certification and differences today

Where things get especially murky is that there were Linux distributions that have previously been Unix certified, showing just how close the gap is between the two. This is because the Linux kernel behaves similarly to Unix, and that’s largely owing to its origins. The two previously Unix-certified Linux distributions were:

  • Inspur’s K-UX (expired in February 2019)
  • Huawei’s EulerOS (expired in September 2022)

Because of these licensing restrictions, it doesn’t make sense for Linux distributions to aim for Unix certification. It’s costly and doesn’t carry much of a benefit to anyone, with the exception of those aforementioned outliers. Because of POSIX standards and compliance, applications that are built for Unix can often be ported to Linux machines easily and vice versa. A lot of shell scripts will run directly on both, though maybe with some minor variations.

Interestingly, macOS is Unix compliant alongside Darwin, the core operating system of macOS, iOS, watchOS, tvOS, iPadOS, visionOS, and bridgeOS. bridgeOS runs on secure enclave T-series chips in Mac computers and is said to be a variant of watchOS. Additional macOS components are built on top of Darwin. Because of this, though, macOS is very likely to be the biggest Unix operating system today.

The other way to get a taste of Unix is to install Solaris, a proprietary operating system owned by Oracle. It’s no longer the kingmaker it once was; in fact, the last major update it received was in August 2018, but it’s been around for a long, long time. It still receives minor updates, with Solaris 11.4 SRU57 released in May this year.

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No matter what though, there’s nothing wrong with either platform. macOS is one of the best and most popular operating systems out there, and various Linux distros like Ubuntu and Fedora are excellent too.

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