Linux Operating System Basics

1. Linux Overview
Linux is a free and open source Unix-like operating system. The kernel of the operating system was first released by Linus Torvalds on October 5, 1991 and became a Linux operating system after adding user-space applications. Linux is also the most famous example of free software and open source software development. As long as the GNU General Public License is followed, any individual or institution is free to use all the underlying source code of Linux, and can also be freely modified and republished. The birth, development, and growth of the Linux operating system always relies on several important pillars, namely the UNIX operating system, the Minix operating system, the GNU program, the POSIX standard, and the Internet network.
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The father of Linux: Linus Torvalds (Linus Torvalds)

2. Linux History
(1) Unix
Unix operating system is a powerful multi-user, multi-tasking operating system, support a variety of processor architectures, according to the classification of the operating system, belong to the time-sharing system, the earliest by Kenthompson, Dennis Ritchie and Douglas McIlroy in 1969 at &t's Bell Labs developed. At present, its trademark rights are owned by the International Open Standards Organization, only UNIX systems that conform to the single UNIX specification can use the UNIX name, otherwise it can only be called Unix-like (unix-like).
(2) Minix
Minix is a UNIX-like computer operating system based on micro-kernel architecture, invented by Andrew S. Tanenbaum. Minix was originally released in 1987, opening all the source code to university teaching and research work. 2000 re-changed to BSD licensing to become free and open source software.
Because of the policy change at/T, after the launch of version 7 Unix, new terms of use were released, the UNIX source code was privatized, and the UNIX source code was no longer available at the university. To avoid copyright disputes, the Professor decided to develop a UNIX-compatible operating system on its own, without using any of the source code, in order to be able to teach the details of the operation of the student operating system in class. He referred to it as a minix, with the meaning of small Unix (Mini-unix).
Minix no code to copy UNIX, so they do not have any inheritance relationship, Minix as the first open source operating system in the history of the internet after the short-term has been rapid development, a large number of people to download learning.
Since Minix is written by one of the professors, there are some loopholes. At this time, there are users found that the vulnerability exists, want to download some patches or write some patches to fix these vulnerabilities, repair found that the effect is good, and then suggested that the professor use these patches to improve the minix, the results, the professor is more stubborn, meaning: In order to maintain the purity of minix, No foreign code is required. In other words, it is not intended to do commercial distribution, so Minux maintained its most primitive demeanor.
(3) Linux
In the next few years, because of the strong operation of the computer hardware industry, the Intel-led x86 system architecture of the personal computer, so the personal computer is quite a popular machine. But at this point, most of the people use DOS operating systems. At this time, a student named Linus Torvalds at the University of Helsinki in Finland did something unusual. At that time, he had a 386 computer, because he did not like the DOS system on his computer, so he thought: since Minix so good, so stable, then I would not transplant it to a personal computer (fortunately because Stallman advocated the open source concept, He was able to access some source Code, and through this idea, O (∩_∩) o~ He was very interested in reading the UNIX core, and remove the more complex core program, it can be applied to the general personal computer x86 system above).
By the year 1991, he finally put 0.02 version of the original code hobby on the network for everyone to download, because hobby by everyone's affirmation, quite a lot of friends put into this work. Finally, in 1994, the first full core version 1.0 was released and caused the current pandemic ... Because of the development of Linux kernel by the virtual team, we are all through the network to obtain the core Linux kernel source code, through their own careful transformation and then back to the Linux community, and then the development of a step-by-step completion of the complete Linux system, as for the Linus Torvalds is the initiator of this group. Thanks to this collective effort, Linus Torvalds Linux as the GNU licensing model for the same benefit!
Linux is Linus Torvalds influenced by Minix. But in the design philosophy, Linux and Minix big phase of the court. Minix uses the principle of microkernel in kernel design, but Linux is the same as the original UNIX with the concept of macro kernel. At the beginning of the development of Linux, the two sides also had a wonderful idea debate on the news group in 1992. Minix's authors and supporters argue that the single-core architecture of Linux is "a big setback to the 70 's", while Linux supporters argue that Minix itself is not practical.

3. Introduction of five Pillars of Linux
(1) UNIX Operating system
The Linux operating system is a cloned version of the UNIX operating system. The UNIX operating system is a time-sharing operating system developed by Ken.thompson and Dennis Ritchie in the American Bell Lab in the summer of 1969 on the DEC PDP-7 small computer. Ken Thompson developed a prototype of the UNIX operating system in one months in the summer of 1969, during his wife's return to his hometown of California, in order to run his favorite Space travel game on an unused PDP-7 computer. At that time, bcpl language (basic combinatorial programming language) was used, and after Dennis Ritchie was rewritten in 1972 with a very strong transplant C language, Unix systems were popularized in tertiary institutions.
(2) Minix operating system
The MINIX system was developed by Andrew S. Tanenbaum (AST). AST is a member of the Vrije University's mathematics and computer science system in Amsterdam, Netherlands, and is a Fellow of ACM and IEEE (few people worldwide are senior members of the two sessions). MINIX, which he compiled for 1987 years, is mainly used for student learning operating system principles. By 1991 the version was 1.5. There are currently two versions in use: Version 1.5 and version 2.0. Of course the current Minix system is free and can be downloaded from many ftp.
For the Linux system, he later expressed his admiration for the developer Linus. But he believes that the development of Linux is due to the fact that he is able to keep the Minix small, so that students can learn in a semester, and therefore not accept the expansion of many people around the world to minix requirements. So under such a premise inspired the Linus to write Linux system. Of course Linus also just caught this good time.
As an operating system, MINIX is not a good person, but it also provides system source code written in C and assembly language. This is the first time that an aspiring programmer or hacker can read the source code of the operating system. At the time, this source code was a secret that software vendors had been guarding carefully.
(3) GNU Program
In the 70 's, the software industry made two leaders who were head-to-head, from Harvard University Bill Gates and Richard M.stallman. The former announced the advent of the age of copyright, and the creation of the glory of the Microsoft Empire, the latter founded the Free software system GNU in 1984, the development of universal Public Copyright Agreement (Generalpubliclicense, referred to as the GPL), Today, the success of Linux is due to the GPL protocol.
All free software under the GPL complies with the "Copyleft" (non-copyright) principle of Richard M. Stallman: Free software allows users to freely copy, modify and sell, but any modifications to their source code must be made publicly available to all users.
The GNU program and the Free Software Foundation FSF (Software Foundation) was founded by Richard M. Stallman in 1984. Designed to develop a complete operating system like UNIX and free software: the GNU system (GNU is the "GNU's not Unix" recursive abbreviation, it is pronounced "guh-new").
A variety of GNU operating systems using Linux as the core are being used extensively. While these systems are often referred to as "Linux," stallman that, strictly speaking, they should be called Gnu/linux systems.
By the early 90, the GNU project had developed many high-quality free software, including the well-known Emacs editing system, the Bash shell program, the GCC series compiler, the GDB debugger, and so on. These software create a suitable environment for the development of Linux operating system. This is one of the foundations in which Linux can be born, so many people now refer to the Linux operating system as the "Gnu/linux" operating system.
(4) POSIX standard
POSIX (Portable Operating System Interface for Computing Systems) is a cluster of standards developed by IEEE and ISO/IEC. The standard is based on existing UNIX practices and experiences that describe the operating system's invocation of the service interface. Applications that are designed to ensure that they can be ported and run on multiple operating systems at the source code level. It was based on the early work of a UNIX user group (Usr/group) in the early 1980. The UNIX user group originally attempted to reconcile the differences between the system V operating system and the call interface of the BERKELEYCSRG BSD operating system. The/usr/group standard was customized in 1984.
In the early 90, the POSIX standard was being finalized at the time of the final vote, which was 1991-1993. At this point, when Linux was just starting, this UNIX standard provided very important information for Linux, enabling Linux to be developed under standard guidance and compatible with most UNIX operating systems. The original Linux kernel source code (version 0.01, version 0.11) has been prepared for the compatibility of Linux systems with POSIX standards. Several symbolic constants for the requirements of the POSXI standard have been defined in the Linux version 0.01 kernel/include/unistd.h file, and Linus wrote in the comments: "OK, this may be a joke, but I'm working on it."
(5) Internet network
The internet is the communication platform of information and resources for Linux development, communication and development.

4. Linux Features
(1) GNU (GNU is not Unit): world-renowned free software project.
(2) GPL (GNU general public License) common license: In order to free the kernel to mark, let it open source down. This protocol defines three things:
The original creator Linus Torvalds retains the copyright;
Other persons are free to dispose of the software;
Copyright cannot be completely controlled.
(3) LGPL (License) Secondary Public License: for the support of more developers, it is much looser than the GPL (it is not necessary to disclose all the source code).

5. Linux features (different from Windows)
Linux is kernel-based and Windows is packaged well
Linux open source, windows closed
Linux free, Windows charges
Linux supports fewer software, Windows supports more software
Linux is primarily a command line, and Windows is primarily graphical
Linux security is high, Windows security is lower than Linux

6, The Basic principles of Linux:

Consists of a small program with a single purpose, and a combination of small programs to accomplish complex tasks;

all documents;

Try to avoid capturing the user interface;

The configuration file is saved in plain text format.

7, Linux common release version

ArchLinux, a rolling-update operating system based on Kiss (Keep It Simple and Stupid).

CentOS, a distributed version developed from Red Hat, is maintained by volunteers and is designed to provide open source and compatible systems with Red Hat 100%.

Chakra, a semi-rolling update release that derives from ArchLinux and uses only the KDE desktop.

Debian, a system that strongly believes in free software and is maintained by volunteers.

Elementary OS: Based on Ubuntu, the interface resembles Mac OS X.

Fedora, the Community edition of Red Hat, often introduces new features for testing.

Gentoo, a release for advanced users, the source code for all software needs to be compiled on its own.

Knoppix, the first live CD release, can be run from removable media, a derived version of Debian.

Kubuntu, Ubuntu using the KDE desktop.

Linux Mint, a system derived from Ubuntu and compatible with Ubuntu.

Mandriva, originally a derivative version of Red Hat, is now maintained by a company of the same name in France.

A derived version of Opengeu,ubuntu.

OpenSUSE, originally isolated by Slackware, is now maintained by Novell.

A derived version of Pclinuxos,mandriva, a very popular distribution maintained by the community.

The commercial version of Red Hat Enterprise Linux,fedora is maintained by Red Hat and provides technical support.

Slackware, one of the earliest distributions, was created in 1993 and maintained by Patrick J. Volkerding.

Ubuntu, a very popular desktop release, is maintained by canonical.

Systems for Gos and other netbooks

8. User and password

The root user is a super administrator of Linux and can operate all permissions on the Linux operating system.

Password complexity rules:

Numbers, letters, special characters

For example: [email protected]

Use 4 type characters wrongly written at least 3 species;

long enough, greater than 7 bit;

use random strings;

regular replacement;

The cycle period is large enough

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Linux Operating System Basics