Unix 简明教程

What is Linux?

What is Linux Operating System?

Linux 操作系统是一组程序，充当计算机和最终用户之间的链接。

The Linux operating system is a set of programs which acts as a link between the computer and the end user.

分配系统资源并协调计算机内部所有详细信息的计算机程序称为 Operating System 或 Kernel 。

The computer programs that allocate the system resources and coordinate all the details of the computer’s internals is called the Operating System or the Kernel.

Why Linux Operating System?

Linux 最初旨在作为其他现有但昂贵的操作系统（特别是 Unix、Windows、Mac OS、MS-DOS、Solaris 等）的替代品。当 Linus Torvalds 在赫尔辛基大学就读时，他决定创建自己的操作系统，并将其作为开源软件，以便全球用户可以为改进该系统提出建议。

Linux was developed to be used as an alternative to other existing but expansive operating systems specially Unix, Windows, Mac OS, MS-DOS, Solaris and others. When Linus Torvalds was studying at the University of Helsinki, he decided to create his own operating system and keep it as Open Sources so that users from around the world can contribute their suggestions for improvements of the system.

  1. Linus Torvalds developed his own kernel and a few programs around it in 1991 which later became a full flagged Operating System and soon it was accepted widely by the Computer Engineers in Corporates, Universities and other Institutes.

  2. Today Linux is one of the most widely used Operating Systems and it come in various variants like Ubuntu, CentOS, Fedora, Debian, openSUSE, RedHat, MX Linux, Arch Linux, Gentoo etc.

  3. Several people can use a Unix computer at the same time; hence Unix is called a multiuser system.

  4. A user can also run multiple programs at the same time; hence Unix is a multitasking environment.

What is Linux Shell?

用户通过一个称为 shell 的程序与内核通信。Shell 是一个命令行解释器；它可以翻译用户输入的命令并将其转换为内核可以理解的语言。

Users communicate with the Kernel through a program known as the shell. The shell is a command line interpreter; it translates commands entered by the user and converts them into a language that is understood by the kernel.

Linux Architecture

以下是一个 Linux 系统的基本框图 -

Here is a basic block diagram of a Linux system −

unix architecture

将所有 Linux 版本结合在一起的主要概念是以下四个基础 -

The main concept that unites all the versions of Linux is the following four basics −

  1. Kernel − The kernel is the heart of the Linux operating system. It interacts with the hardware and most of the tasks like memory management, task scheduling and file management.

  2. Shell − The shell is the utility that processes your requests. When you type in a command at your terminal, the shell interprets the command and calls the program that you want. The shell uses standard syntax for all commands. C Shell, Bourne Shell and Korn Shell are the most famous shells which are available with most of the Unix variants.

  3. Commands and Utilities − There are various commands and utilities which you can make use of in your day to day activities. ftp, ssh, cp, mv, cat and grep, etc. are few examples of commands and utilities. There are over 250 standard commands plus numerous others provided through 3rd party software. All the commands come along with various options.

  4. Files and Directories − All the data of Unix is organized into files. All files are then organized into directories. These directories are further organized into a tree-like structure called the filesystem.

Linux Applications

Linux 是一款开源操作系统，广泛用于服务器、Web 服务器、超级计算机和嵌入式系统等。Linux 系统最大的优点是您会找到大量的免费开源软件应用程序。

Linux is an open-source operating system widely used in servers, web servers, supercomputers, and embedded systems etc. The best part of the Linux system is that you will find a vast range of free and open-source software applications.

本节列出了 Linux 操作系统上免费提供的几个重要软件应用程序：

This section lists a few important software applications freely available on Linux Operating System:

  1. VLC Media Player - VLC Media Player is a free and open-source media player software that can play almost all types of media files, including audio and video. VLC media player is widely regarded as one of the best media players in the market.

  2. GNU Image Manipulation Program - GIMP is a free and open-source image editing program that can be used for tasks ranging from image retouching to graphic design. GIMP provides great functionality for image manipulation, color correction, cloning, and selection. It also supports layers, masks, and channels, allowing for more advanced editing techniques.

  3. FileZilla - FileZilla is a free and open-source FTP client that transfers files between a local computer and a remote server. It is known for its easy and user-friendly interface and ease of use to transfer files between two computers.

  4. Web Servers - The most frequent application of Linux is to use it like a Web Server. There are several web server softwares (Apache, NGinx etc) available which can be installed and use on Linux.

  5. Web Browsers - Linux provides an easy way to browse the Internet with the help of various Web Browsers. Firefox is the default browser for various Linux distributions such as Linux Mint and Ubuntu.

  6. LibreOffice - LibreOffice is free and an open source software which provides a great alternative for office suites. LibreOffice supports various file formats such as DOC, DOCX, PPT, PPTX, XLSX, etc.

  7. Vim - This is one of the best text Editor available on Linux. This is loved by millions of software developers around the world.

Linux Licensing

Linux 是自由且开放源代码软件应用的最合适的例子之一。在各个许可证（如 GNU 通用公共许可证 (GPL)）的条款下，任何人都可以出于商业或非商业目的使用、修改和分发 Linux 源代码。

Linux is one of the most suitable examples of free and open-source software applciation. Linux source code may be used, modified, and distributed commercially or non-commercially by anyone under the terms of its respective licenses, such as the GNU General Public License (GPL).

Linux 内核根据 GPLv2 许可，其中 system calls 的例外授予了调用内核的代码而不使用 GPL 许可的权限。

The Linux kernel is licensed under the GPLv2, with an exception for system calls that allows code that calls the kernel via system calls not to be licensed under the GPL

Linux 根据 GNU 通用公共许可证 (GPL) 许可，而它是一种自由软件许可，授予用户运行、研究、共享和修改软件的自由。

Linux is licensed under the GNU General Public License (GPL), which is a free software license that grants users the freedom to run, study, share, and modify the software.