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This article is to share with you about the relationship between Linux and Unix, the editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

Unix and BSD

When it comes to Linux, we first need to understand Unix.

Unix is an operating system that has existed in AT&T Bell Labs for a long time. The project is led by two famous computer scientists, Ken Thompson and Dennis Ritchie.

The official development of Unix began in the summer of 1969, with the first version of Unix released in March 1971 and the second version in 1972.

If you type the date command on a Linux machine or MacOS, you will get a number called the Unix timestamp. This number is the number of seconds since 00:00:00 on January 1, 1970. Why January 1st, 1970? You should know the answer by now, when Unix was in the process of development.

Ken Thompson and Dennis Ritchie created the B language, a programming language supported in earlier versions of Unix. Then, in 1972, Ritchie rewrote B, improved it even better, and became C, which is still very popular today. Most of the later Unix components were written in C.

In the late 1970s, AT&T shared Unix with educational institutions and external business organizations, which led to the birth of many different versions of Unix. The most prominent of these is the educational version built by the computer Systems Research Group at the University of California, Berkeley. This version is widely known as Berkeley Software Distribution, or BSD.

At first, BSD was based on Unix design and code base, but later, the versions of Unix and BSD became more and more distinctive, leading to a "standard competition" between the Unix BSD version and the AT&T codenamed System V version of Unix. In the end, the victory belongs to SystemV. Later versions of BSD brought System V closer to learning and incorporated generally accepted standards.

With the emergence of open source projects such as FreeBSD, NetBSD, and OpenBSD, the history of the BSD branch has come to an end. The final version of BSD was launched in 1995. The final version of Unix is the Unix 10 version released in 1989 and was developed by Bell Laps.

Although development was stopped a long time ago as the official version of Unix and BSD, many current operating systems (from closed source to open source) are based on these two branches.

The more famous and successful commercial version may be Apple's MacOS. Currently, iOS, watchOS and tvOS systems and other Apple operating systems are based on the BSD platform. MacOS is also one of the few operating systems considered to be UNIX-like.

GNU

In the course of the development of Unix, an important thing happened in 1983, which was the premise of drastic changes later.

In September 1983, Richard Stallman announced the introduction of the GNU program (GNU stands for GNU, not Unix).

The goal of the GNU project is to create a free, unix-like operating system in which people are free to copy, develop, modify and distribute software without restrictions.

Keep in mind that derivative versions of Unix and Unix were originally closed source and copyrighted.

In 1985, Richard founded the Free Software Foundation (FSF), a non-profit organization that promotes freedom in software development.

The GNU project created many important products, such as GNU Compiler Collection (gcc), GNU Debugger, GNU Emacs text editor (Emacs), GNU build automator (make), and the most widely used today: the GNU General Public license (GPL).

The GNU project has made many great achievements and created many tools similar to Unix. However, GNU still lacks an important component: the kernel (the part that handles control and communication with hardware devices (CPU, RAM, devices, etc.).

Linux

On August 25, 1991, a Finnish student named Linus Torvalds introduced a personal product that later became the Linux kernel.

Linus's project quickly attracted the attention of many individuals and organizations.

The combination of the Linux kernel and GNU software created the first completely free operating system. Its name is GNU/Linux.

Note:

Linux itself is just a kernel, it is not a complete operating system. The operating system used on computers is called GNU / Linux, and people simply call it Linux.

The Linux operating system does not use or share any part of the Unix or BSD code. It is newly built by Linus and GNU Project and becomes a clone of Unix. This is why Linux and current Unix descendant operating systems such as MacOS have a lot in common.

It is generally believed that commands such as ls, cat, and grep are essentially the same whether they are run on MacOS or Linux. But they are actually two different tools. You can get an introduction to the GNU version by running grep--help or man grepon on Ubuntu and an introduction to the BSD version on Mac. Of course, most GNU and BSD (Unix) tools are the same for every option, but there are exceptions.

You can install the GNU version on Mac instead of the default version, which allows you to use the same commands as Linux.

Linux distribution

Linux is only part of the kernel, and GNU provides the necessary tools to run on that kernel. However, we are free to decide the kernel configuration.

Some organizations and companies create complete operating system distributions called Linux distributions by combining the Linux kernel with utilities or package managers.

Today, there are countless Linux distributions, many of which are very familiar and popular. Some of the most commonly used distributions include: Ubuntu, Debian, CentOS, Fedora, Redhat, Linux Mint, etc.

A distribution can be built on top of another distribution. In fact, the distributions I mentioned above have a lot of close relationships with each other. The two oldest distributions (still in use today) are Slackware and Debian. They were founded in 1993.

Descendant branches of Debian may also be larger distributions. In addition to Debian itself, the main representatives of this branch are Ubuntu (built on Debian), Linux Mint (built on Ubuntu), and Kali Linux.

Another well-known distribution is Redhat, and the main release is Red Hat Enterprise Linux (RHEL), which is aimed at Redhat's enterprise customers. In addition to offering RHEL as a paid distribution, Redhat also offers another free distribution to the community, Fedora.

In fact, the Fedora version is usually tested first for feedback and bug fixes, and then RHEL is built on a stable version of Fedora. In addition, Redhat provides free source code for almost all components of RHEL, and the community can build distributions (similar to RHEL). CentOS is a community version (not supported by Redhat), completely free, and is an enterprise-quality distribution similar to RHEL.

Learn and be familiar with Linux. In my opinion, Ubuntu (or Debian) and CentOS will be the combination you should be familiar with.

There are other operating systems based entirely on the Linux kernel. One of the most prominent is Android. Android may be a popular operating system that uses the Linux kernel.

Linux kernel version

You can view a list of Linux kernel versions on the https://www.kernel.org/ on the project home page.

To check the kernel version on the distribution you are using, you can use the uname-r command.

Using the uname-a command will print out the entire system information and uname-o will print out the operating system name. The result is that the operating system name is GNU / Linux, not just Linux.

Unix-like

MacOS is one of the few operating systems certified by Single UNIX Specification (SUS), and is considered to be a Unix-like operating system.

Currently, the UNIX trademark is copyrighted by Open Group (please note that the letters in the UNIX trademark name are capitalized, while for the operating system, we can write as Unix or UNIX).

"Unix-like (Unix-like") "is used to represent an operating system with SUS certification, and can use the UNIX brand.

The question is: according to the above definition, is Linux a "Unix-like" operating system? The answer is no. Currently, the Linux distribution does not allow the use of the UNIX trademark.

In addition to interpreting "Unix-like" as an integral part of SUS, it has been suggested that the word "Unix-like" should be used in a broader sense. Specifically, it can be divided into three categories:

Genetic UNIX: an operating system that is only directly related to the code base of the Bell Labs Unix version.

Trademark UNIX: the operating system meets the SUS requirements and can use the UNIX trademark.

Functional UNIX: "similar to Unix" operating system, Linux can be classified as such.

The following is a schematic diagram that describes the formation and development of Unix and the operating system closely related to Unix.

This is what the relationship between Linux and Unix is. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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