Lkd 3rd reading notes -- Chapter 1st/history of Linux

Along came Linus: Introduction to Linux

Linus Torvalds released the first version of Linux in 1991. This version of Linux can only run on Intel 80386 processors, which were then cutting-edge processors. Linus was also a student at Helsinki University (Helsinki is the capital name of Finland) and often worried about having no powerful and free UNIX operating system. At that time, the mainstream PC operating system was Microsoft's dossystem. For Torvalds, this system was not very useful except to use it to play games such as the Persian prince. So Linus switched to minix, a low-cost UNIX system developed for educational purposes. However, according to the license agreement of the minix system, it is almost impossible to modify and submit code for the operating system, and the design of the minux system is not easy to understand, which makes Linus very comfortable.

 

To get rid of these dilemmas, just as all college students do, Linus decides to write its own operating system. Starting from writing a simple terminal simulator, Linus uses its own terminal to connect to the large UNIX System of the school. With the completion of his academic course, his terminal simulator is also evolving. After that, Linus has its own operating system, which is not yet mature but fully functional. In 1991, he uploaded an earlier version to the Internet, which is Linux.

 

After the release of Linux, many users were quickly merged. More importantly, it quickly attracts many hackers to join the ranks of developers and add, modify and improve code together. Thanks to the Linux License Agreement, Linux soon became a collaborative project composed of many developers.

 

Today, Linux is a fully functional operating system that can run on a variety of hardware architectures including alpha, arm, PowerPC, SPARCx86-64. Linux runs in a supercomputer cluster from small to large to full room. Linux consumes the least power to build the largest data center. Today, the interest of commercial organizations in Linux is also increasing, whether it is emerging Linux companies such as RedHat or existing large companies such as IBM, all provide Linux-based solutions for the embedded, mobile, desktop, and server markets.

 

Linux is similar to Unix, but it is not UNIX. Although it draws a lot of inspiration from UNIX and implements UNIX APIs (defined by POSIX and single UNIX specification ), however, it does not directly derive from the Unix source code like other UNIX variants. As we expected, although Linux is not directly related to other UNIX implementations, it does not violate the general design goals of Unix or break the standard programming interfaces of UNIX.

 

One of the biggest characteristics of Linux is that it is not a commercial product, but a collaborative development project through the Internet. Although Linus is the founder and maintainer of Linux, Linux is still being improved through loose developers, and anyone can contribute to Linux. Most of the Linux kernel and Linux software are free and open-source. Specifically, the Linux kernel is released based on gpl2.0. Therefore, you can download the source code for free and make any modifications you want. The only thing you need to comply with is that if you publish your changes, you must provide all the rights you have to use the code, including making your source code public.

 

Linux may represent many meanings in many people's minds. A basic Linux system includes: kernel, C library, tool chain, and basic system tools such as logon program and shell. Linux systems can also include modern X Windows systems that implement a complete desktop environment, such as gnome. Countless free and commercial applications can run on Linux. In this book, when we talk about Linux, it is usually used to refer to the Linux kernel, otherwise it will be explained separately. Strictly speaking, Linux refers to the kernel.