Entering the Linux world [1. Overview of Linux]

Linux system learning

Entering the Linux world [1. Overview of Linux]

Entering the Linux world [2. VM and Linux installation]

Entering the Linux world [3. Linux files and paths]

Enter the Linux world [4, Linux basic commands 1]

Enter the Linux world [5, Linux basic commands 2]

Enter the Linux world [6, Linux editor vim]

Enter the Linux world [7, Linux network and snapshot and clone]

Enter the Linux world [eight, Linux shell commands]

Entering the Linux world [Nine, Linux software installation]

Chapter 1 Linux Overview

1. Operating system

​ Definition: Operating System (OS for short) is a computer program that manages computer hardware and software resources

​ Function: It is to encapsulate the operation of the hardware device in the computer system, to be called by the application software, and to provide an operation interface for the user to interact with the system.

​ In our common operating system there are

​PC side

​ 1、Windows

​ 2、MacOS

​ 3、Linux

​Mobile OS

1. Android and Apple

2. The history of the development of the operating system

​ Unix

​ Before 1965, computers were not as common as they are now. It was not accessible to ordinary people, unless it was a military or academic research institution. At that time, the mainframe could provide up to 30 terminals (30 keyboards, monitors, etc.) ), connect a computer

​ In order to solve the problem of insufficient quantity

​ In 1965, the Multics project was jointly launched by Bell Labs, MIT and General Electric in order to allow the mainframe to support 300 terminals.

​ Around 1969, the progress of this project was slow and funds were short, so Bell Labs withdrew from the research

​ Ken Thompson, who withdrew from this project in 1969, was bored in the laboratory. In order to run the "Star Trek" parade on an idle computer, he used a computer around August when his wife was visiting relatives. A prototype of the Unix operating system was written in a month

​ In 1970, Ken Thompson of Bell Laboratories in the United States, based on the BCPL language, designed a very simple and very close to the hardware B language (taking the initials of BCPL), and he wrote the first UNIX operating system in the B language .

​ Because the B language is not cross-platform, in order to be able to run this great Unix operating system on other computers, Dennis Ritchie and Ken Thompson are going to study a better language based on the B language

​ Ken Thompson (left) and Dennis Ritchie (right)

​ In 1972, Dennis Ritchie of Bell Labs in the United States finally designed a new language based on the B language. He took the second letter of BCPL as the name of the language, which is the C language.

​ In early 1973, the main body of the C language was completed. Thompson and Ritchie couldn't wait to start using it to completely rewrite the now famous Unix operating system

​ Early Unix systems were developed for specialized hardware systems, and different vendors developed specialized Unix operating systems for their own servers.

Minix

​ Because of AT&T (General Electric) policy changes, after the launch of Version 7 Unix, new terms of use were issued to privatize the UNIX source code, and the UNIX source code can no longer be used in universities. Professor Andrew S. Tanenbaum (Tanenbaum) decided to develop a UNIX-compatible operating system without using any AT&T source code in order to teach students the practical details of operating system operation in class to avoid copyright infringement. controversy. He called it MINIX with the meaning of mini-UNIX (mini-UNIX).

​ Linux

​ Because Minix is ​​only used for teaching, so the function is not strong, so Torvalds used GNU bash as a development environment, gcc as a compilation tool, and wrote the Linux kernel-v0.02, but at the beginning Linux was not compatible with Unix, that is, running on Unix The application program cannot run on Linux, that is, the interface between the application program and the kernel is inconsistent, because Unix follows the POSIX specification, so Torvalds modified Linux and followed the POSIX (Portable Operating System Interface, he standardized the application program and the kernel interface specification); at the beginning, Linux was only applicable to 386, and later, with the help of netizens all over the world, it was finally compatible with a variety of hardware;

​ The most famous student user of Minix is ​​Linus Torvalds, who used the Minix operating platform to build the kernel of a new operating system at the University of Helsinki in Finland, which he called Linux.

​ The Linux kernel was originally written as a hobby by **** *Finland ********* *person Linus Torvalds***** while studying at the University of Helsinki of.

​ Linux is a set of Unix-like operating systems that are free to use and spread freely. It is a multi-user, multi-tasking, multi-threading and multi-CPU operating system based on POSIX and UNIX.

Linux can run major UNIX tools, applications, and network protocols. It supports 32-bit and 64-bit hardware. Linux inherits Unix's network-centric design idea and is a multi-user network operating system with stable performance.

​ At present, the well-known distributions on the market are: Ubuntu, RedHat, CentOS, Debain, Fedora, SuSE, OpenSUSE.

​ The difference between Unix and Linux

​ The biggest difference between Linux and UNIX is that the former is free software with open source code, while the latter is traditional commercial software with intellectual property protection for source code .
​ This should be the biggest difference between them. This difference is reflected in the fact that users have a high degree of autonomy for the former, but they can only passively adapt to the latter; this difference is also reflected in the fact that the development of the former is
in a In a completely open environment, the development of the latter is completely in a black box, and only relevant developers can access the prototype of the product .
​ The specific differences are as follows:

UNIX系统大多是与硬件配套的，而Linux则可运行在多种硬件平台上.
UNIX是商业软件，收费，而Linux是自由软件，免费、公开源代码的.
Linux商业化的有RedHat Linux 、SuSe Linux、slakeware Linux、国内的红旗等，还有Turbo Linux.
Unix主要有Sun 的Solaris、IBM的AIX,　HP的HP-UX，以及x86平台的的SCO Unix/Unixware.

3. Linux distribution version

​ The kernel (kernel) is the heart of the system. It is the core program that runs programs and manages hardware devices such as disks and printers. It provides an abstraction layer between raw devices and applications.

​ The Linux kernel version is divided into a stable version and a development version. The two versions are interrelated and circulate each other:

- 稳定版：具有工业级强度，可以广泛地应用和部署。新的稳定版相对于较旧的只是修正一些bug或加入一些新的驱动程序。
- 开发版：由于要试验各种解决方案，所以变化很快。

​ Kernel source URL: http://www.kernel.org All modifications to the Linux source code from all over the world will eventually be aggregated to this website, and the open source community led by Linus will screen and modify it to finally decide whether to enter the Linux mainline in the kernel source code.

​ Linux distributions (also known as GNU/Linux distributions) usually include application software including desktop environments, office suites, media players, and databases.

ranking	Version	describe
1	MX Linux	Based on Debian and antiX
2	Linux Mint	Based on Ubuntu and Debian
3	Ubuntu	One of the top Linux distributions
4	Elementary OS	Based on Debian
5	Manjaro Linux	Based on Arch Linux
6	Zorin OS	Based on Debian
7	Fedora	Leading position in software technology
8	Debian	designed to be very stable
9	CentOS	Best Linux for Enterprise Based on Fedora and Red Hat
10	Kali Linux	Based on Debian

        Linux能做什么？

        Linux可作为企业级服务器，或嵌入式开发平台也包含个人桌面系统。包含虚拟化、数据库服务器、Web服务器、开发平台等等

        哪些人要学习Linux？

        Linux管理员，oracle管理员，网络工程师，程序开发者等等。Linux系统涉及方面非常广泛，生态也越来越强大，非常适合大家学习

​Applications in the field of personal

​ This field is the weakest link of traditional linux applications. Traditional linux has been suppressed by windows due to the shortcomings of simple interface, complex operation, and few application software. However, in recent years, with the rise of excellent desktop environments such as ubuntu and fedora, at the same time Major hardware manufacturers have increased their support, and the share of Linux in the personal desktop field is gradually increasing.

典型代表：ubuntu、fedora、suse linux

​Server area

The application of linux in the server field is an important branch of it

​ The characteristics of linux such as free, stable, and high-efficiency have been well reflected here, but it was also greatly restricted in the early days due to reasons such as maintenance and operation. However, in recent years, the linux server market has been rapidly improved, especially in some Especially in the high-end field

典型代表： Red Hat公司的AS系列
          完全开源的debian系列
          suse EnterPrise 11系列等

​Embedded field

In recent years, the application of linux in the embedded field has been rapidly improved

​Linux has stable operation, good support for the network, low cost, and software can be tailored according to needs. The minimum kernel can reach several hundred KB, etc., which has greatly improved its application in the embedded field in recent years.

小贴士：Minix没有火起来的原因

Andrew Tanenbaum教授在发布Minix3时，接受采访时他透露MINIX3将移植到ARM架构。他说，MINIX3没有统治世界是源于他在1992年犯下的一个错误，当时他认为BSD必然会一统天下，因为它是一个更稳定和更成熟的系统，其它操作系统难以与之竞争。

因此他的MINIX的重心集中在教育上。四名BSD开发者已经成立了一家公司销售BSD系统，他们甚至还有一个有趣的电话号码1-800-ITS-UNIX。

然而他们正因为这个电话号码而惹火上身。美国电话电报公司因电话号码而提起诉讼。

官司打了三年才解决。在此期间，BSD陷于停滞，而Linux则借此一飞冲天。

 他的错误在于没有意识官司竟然持续了如此长的时间，以及BSD会因此受到削弱。如果美国电话电报公司没有起诉，Linux永远不会流行起来，BSD将统治世界。

1-800-ITS-UNIX。

Yet they're getting pissed off over the phone number. AT&T sued over the phone number.

The lawsuit took three years to resolve. During this period, BSD stagnated, and Linux took advantage of it to soar.

His mistake was not knowing that the lawsuit went on for so long, and that BSD would be weakened by it. If AT&T hadn't sued, Linux would never have caught on and BSD would have ruled the world.