If you are a software developer in your 20s or 30s, you have grown up in a world dominated by Linux. For decades, it has been an important participant in the data center, although it is difficult to find a clear operating system market share report, but Linux's data center operating system share may be as high as 70%, while Windows and its variants cover almost all the remaining The percentage. Developers using any mainstream public cloud service can expect the target system to run Linux. In recent years, with the application of Android and Linux-based embedded systems in smart phones, TVs, cars, and other devices, Linux has become widely available.
Even so, most software developers, even those who grew up in this long-established "Linux revolution," have heard of Unix. It sounds like Linux, and you may have heard people use these terms interchangeably. Or you may have heard that Linux is known as a "Unix-like" operating system.
So what is Unix? The manga likes to draw it like a shaman with a “gray beard†image, sits behind a glowing green screen, writes C code and shell scripts, and is powered by old-fashioned, drip-feeding coffee. However, the history of Unix is ​​far richer than those of bearded C programmers in the 1970s. Although articles detailing the history of Unix and "Unix versus Linux" are commonplace, this article will provide a high-level background and list the major differences between these complementary worlds.
The origin of Unix
The history of Unix began at AT&T Bell Laboratories in the late 1960s. A group of programmers wanted to write a multi-tasking, multi-user operating system for the PDP-7. The two most famous members of this Bell Labs research team are Ken Thompson and Dennis Ritchie. Although many concepts of Unix are derivatives of its predecessor (Multics), the Unix team decided in the 1970s to rewrite the small operating system in C language, which is why Unix is ​​distinguished from other operating systems. At the time, there were few operating systems, let alone portable operating systems. On the contrary, because of their design and nature of the underlying language, the operating system is closely related to the hardware platform they have written. Refactoring Unix and Unix via C language can now be ported to many hardware architectures.
In addition to this new portability, the rapid expansion of Unix to other research and academic institutions outside of Bell Labs and even commercial use is due to the fact that several key points of operating system design principles have attracted users and programmers. The first is that Ken Thompson's Unix philosophy has become a powerful model for modular software design and computing. Unix philosophy recommends using a combination of small, specialized programs to accomplish complex, overall tasks. Since Unix is ​​designed around files and pipes, the combination of input and output programs of this "pipe" mode is a set of linear input operations that are still popular. In fact, the current cloud-as-a-service (FaaS) or serverless computing model is credited with many traditions of Unix philosophy.
Rapid growth and competition
By the late 1970s and 1980s, Unix became the origin of an operating system family that spanned research and academic institutions as well as the growing commercial Unix operating system business. Unix is ​​not open source software and Unix source code can be licensed through an agreement with its owner, AT&T. The first known software license was sold to the University of Illinois at the University of Illinois in 1975.
Unix developed rapidly in academia. During Ken Thompson’s academic break in the 1970s, Berkeley became an important activity center. Through a variety of Unix-related activities in Berkeley, a new delivery method for Unix software was born: Berkeley Software Distribution (BSD). Initially, BSD was not a replacement for AT&T Unix, but an add-on that resembles additional software and features. In 1979, when 2BSD (second edition Berkeley software release) appeared, Berkeley graduate student Bill Joy had added now very famous programs such as vi and C shell (/bin/csh).
In addition to being BSD, one of the most popular branches of the Unix family, Unix commercial products broke through the 1980s and 1990s, including HP-UX, IBM's AIX, Sun's Solaris, Sequent and Xenix et al. As the branch grew from its roots, "Unix War" began and standardization became the new focus of the community. The POSIX standard was born in 1988, and other standardization follow-up work has also begun through The Open Group in the 90s.
During this period, AT&T and Sun released System V Release 4 (SVR4), which is used by many commercial vendors. In addition, BSD series operating systems have been growing for many years, and eventually some open source variants are released under the now familiar BSD license. This includes FreeBSD, OpenBSD, and NetBSD, each with slightly different target markets in the Unix server industry. These Unix variants are still in use today, although people have seen their server market share shrink to a single digit (or lower). In all current Unix systems, BSD may have the largest installed base. In addition, each Apple Mac hardware device can be counted as BSD from a historical perspective, because OS X (now macOS) operating system is a BSD derivative product.
Although the entire history of Unix and its academic and commercial variants may require more space, for the sake of our article, let us discuss the rise of Linux.
Go to Linux
Today we are talking about the Linux operating system is actually a combination of two efforts in the early 90s. Richard Stallman wanted to create a truly free and open source alternative to a proprietary Unix system. He is developing utilities and programs under the name of GNU. This is a recursive statement that means "GNU's not Unix!". Although there was a kernel project in progress at the time, it turned out to be a very difficult task, and without the kernel, the dream of free and open source operating systems could not be realized. This is what Linus Torvald did - producing a working and viable kernel that he called Linux - which brought the entire operating system to life. Since Linus uses several GNU tools (such as the GNU compiler collection, GCC), the combination of GNU tools and the Linux kernel is the perfect match.
The Linux distribution uses GNU's components, the Linux kernel, MIT's X-Windows GUI, and other BSD components that can be used under the open source BSD license. Early releases of distributions such as Slackware and Red Hat gave the "ordinary PC users" of the 1990s an opportunity to enter the Linux operating system and allow them to use many features specific to Unix systems in their work and academic life. Utilities.
Since all Linux components are free and open source code, anyone can create a Linux distribution with some effort, so the total number of releases will soon reach hundreds. Today, distrowatch.com lists 312 unique Linux distributions in various forms. Of course, many developers use Linux through cloud providers or use popular free distributions such as Fedora, Canonical's Ubuntu, Debian, Arch Linux, Gentoo, and many other variations. With many companies including IBM migrating from proprietary Unix to Linux and providing middleware and software solutions, it has become feasible for commercial Linux products to provide support on free and open source components. Red Hat has established a commercial support model around Red Hat Enterprise Linux (Red Hat Enterprise Linux). The German vendor SUSE also provides this model using SUSE Linux Enterprise Server (SLES).
Compare Unix and Linux
So far, we have learned about the history of Unix and the rise of Linux, as well as the GNU/Free Software Foundation's support for Unix's free and open source alternatives. Let's take a look at the differences between these two operating systems. They have many common traditions and many of the same goals.
From the user experience point of view, the two are similar! The great attraction of Linux is the availability of operating systems on many hardware architectures, including modern PCs, and the ability to use tools familiar to Unix system administrators and users.
Due to POSIX's standards and compliance, software written on Unix can be compiled against the Linux operating system, usually with only a small amount of porting workload. In many cases, Shell scripts can be used directly on Linux. Although some tools have slightly different flags or command line options between Unix and Linux, many tools are the same in both.
On the one hand, it should be noted that the prevalence of macOS hardware and operating systems as the main development platform for Linux may be attributed to the BOS-like macOS operating system. Many tools and scripts for Linux systems can easily work within the macOS terminal. Many open source software components on Linux are easily available through tools such as Homebrew.
The other differences between Linux and Unix are primarily related to the licensing model: open source and proprietary licensing software. In addition, a common kernel that affects software and hardware vendors is missing from the Unix distribution. For Linux, vendors can create device drivers for specific hardware devices and expect it to run on most distributions to a reasonable extent. Due to the commercial and academic branches of the Unix family, vendors may have to write different drivers for variants of Unix and require licenses and other related permissions to access the SDK or software distribution model to span multiple binary device drivers. Unix variants.
As these two communities have matured over the past decade, many of the advantages of Linux have been adopted in the Unix world. When developers need features from GNU programs that are not part of Unix, many GNU utilities are available as attachments to Unix systems. For example, IBM's AIX provides an AIX Toolbox for Linux applications containing hundreds of GNU packages (such as Bash, GCC, OpenLDAP, and many other packages) that can be added to the AIX installation package to simplify Linux Transitions between Unix-based AIX systems.
Proprietary Unix is ​​still alive and not bad, and many major vendors have promised to support their current version until 2020. It goes without saying that Unix will always appear in the foreseeable future. In addition, the BSD branch of Unix is ​​open source, and NetBSD, OpenBSD, and FreeBSD have a strong user base and open source community. They may not be as prominent or active as Linux, but in recent server reports, they are in areas such as Web services. Far more than the number of proprietary Unix.
Linux has shown that its significant advantage over Unix is ​​its availability on a large number of hardware platforms and devices. The Raspberry Pi Raspberry Pi is popular with amateurs. It is powered by Linux and opens the door to various IoT devices running Linux. We have already mentioned Android devices, cars (including Automotive Grade Linux) and smart TVs, of which Linux has a huge market share. Every cloud provider on the planet offers virtual servers running Linux, and many of today's most popular native cloud architectures are based on Linux, whether you are talking about container runtimes or Kubernetes, or whether many are popular Server platform.
One of the most significant advantages of representing Linux is the transformation of Microsoft in recent years. If you tell software developers ten years ago that the Windows operating system will "run Linux" in 2016, most of them will laugh hysterically. But the existence and popularity of the Windows Linux subsystem (WSL), and the recently announced features of the Windows porting version of Docker, including support for LCOW (Linux Containers on Windows), all testify to the impact of Linux in the entire software world— — and obviously will continue to exist.
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