Operating System 简明教程

Operating System - Linux

Linux 是 UNIX 操作系统流行版本之一。它是开源的，因为它的源代码是免费提供的。它免费使用。Linux 的设计考虑了 UNIX 兼容性。它的功能列表与 UNIX 非常相似。

Linux is one of popular version of UNIX operating System. It is open source as its source code is freely available. It is free to use. Linux was designed considering UNIX compatibility. Its functionality list is quite similar to that of UNIX.

Components of Linux System

Linux 操作系统主要有三个组件

Linux Operating System has primarily three components

  1. Kernel − Kernel is the core part of Linux. It is responsible for all major activities of this operating system. It consists of various modules and it interacts directly with the underlying hardware. Kernel provides the required abstraction to hide low level hardware details to system or application programs.

  2. System Library − System libraries are special functions or programs using which application programs or system utilities accesses Kernel’s features. These libraries implement most of the functionalities of the operating system and do not requires kernel module’s code access rights.

  3. System Utility − System Utility programs are responsible to do specialized, individual level tasks.

linux os

Kernel Mode vs User Mode

内核组件代码在称为 kernel mode 的特殊特权模式下执行，可以完全访问计算机的所有资源。此代码表示一个进程，在单个地址空间中执行，不需要任何上下文切换，因此非常高效且快速。内核运行每个进程并向进程提供系统服务，向进程提供对硬件的受保护访问。

Kernel component code executes in a special privileged mode called kernel mode with full access to all resources of the computer. This code represents a single process, executes in single address space and do not require any context switch and hence is very efficient and fast. Kernel runs each processes and provides system services to processes, provides protected access to hardware to processes.

不需要在内核模式下运行的支持代码位于系统库中。用户程序和其他系统程序在 User Mode 中运行，它们无法访问系统硬件和内核代码。用户程序/实用程序使用系统库访问内核功能以获取系统的底层任务。

Support code which is not required to run in kernel mode is in System Library. User programs and other system programs works in User Mode which has no access to system hardware and kernel code. User programs/ utilities use System libraries to access Kernel functions to get system’s low level tasks.

Basic Features

以下列出了 Linux 操作系统的一些重要功能。

Following are some of the important features of Linux Operating System.

  1. Portable − Portability means software can works on different types of hardware in same way. Linux kernel and application programs supports their installation on any kind of hardware platform.

  2. Open Source − Linux source code is freely available and it is community based development project. Multiple teams work in collaboration to enhance the capability of Linux operating system and it is continuously evolving.

  3. Multi-User − Linux is a multiuser system means multiple users can access system resources like memory/ ram/ application programs at same time.

  4. Multiprogramming − Linux is a multiprogramming system means multiple applications can run at same time.

  5. Hierarchical File System − Linux provides a standard file structure in which system files/ user files are arranged.

  6. Shell − Linux provides a special interpreter program which can be used to execute commands of the operating system. It can be used to do various types of operations, call application programs. etc.

  7. Security − Linux provides user security using authentication features like password protection/ controlled access to specific files/ encryption of data.

Architecture

下图显示了 Linux 系统的架构 −

The following illustration shows the architecture of a Linux system −

linux architecture

Linux 系统的架构由以下层组成 −

The architecture of a Linux System consists of the following layers −

  1. Hardware layer − Hardware consists of all peripheral devices (RAM/ HDD/ CPU etc).

  2. Kernel − It is the core component of Operating System, interacts directly with hardware, provides low level services to upper layer components.

  3. Shell − An interface to kernel, hiding complexity of kernel’s functions from users. The shell takes commands from the user and executes kernel’s functions.

  4. Utilities − Utility programs that provide the user most of the functionalities of an operating systems.