Linux—网络时代的操作系统大学毕业论文外文文献翻译及原文

《Linux操作系统》Linux操作系统Linux是一款由Linus Torvalds开发的开源操作系统，它是基于Unix的操作系统，具有免费、自由、安全、稳定等特点。

由于它的开源性质和强大的命令行接口，Linux一直以来都是程序员、系统管理员和服务器管理员等人员的首选操作系统。

Linux的历史早在1991年，Linus Torvalds还是芬兰赫尔辛基大学的大学生时，他开始开发一款操作系统，这个操作系统的灵感来源于他对Minix操作系统的不满，他希望能够开发一款能够完全满足自己需求的操作系统，这就是Linux的雏形。

之后，Linus Torvalds把这个操作系统的源代码公开，让全世界的人都可以免费使用和修改它。

最初，Linux并不太受人们的关注，因为它不如那些商业操作系统那样好听、好看，而且初期的版本还有很多漏洞和不完善的地方。

但是，随着互联网的快速发展，Linux逐渐成为了互联网服务器和个人电脑的操作系统之一，越来越多的人认识到了Linux所具有的各种特点和优点。

Linux的优点Linux系统具有很多优点，下面，我们来看看其中的一些。

1.带来了更低的成本。

Windows和Mac OS X等商业操作系统价格通常非常昂贵，而Linux是开源的，因此他可以带来更低的成本，甚至免费的操作系统体验。

2.良好的安全性。

由于Linux开源的特性，许多开源爱好者可以为Linux 系统贡献代码，极大提高了系统的安全性。

同时，Linux系统自身具有较高的安全性，它可以像Unix这样的操作系统管理权限，用户及程序权限，从而防止黑客攻击等安全问题出现。

3.强大的命令行。

Linux操作系统有很强的命令行功底，这使得没有图形界面的服务器也可以轻松地进行管理。

在Linux下，我们可以通过命令行直接操作系统，完全不需要依赖图形界面。

4.高的可定制性。

Linux开源且免费，在使用时，可以根据个人或企业需求进行定制，获得更高效的体验。

关于linux范文Linux操作系统诞生于1991 年10 月5 日(这是第一次正式向外公布时间)。

Linux存在着许多不同的Linux版本，但它们都使用了Linux内核。

Linux可安装在各种计算机硬件设备中，比如手机、平板电脑、路由器、视频游戏控制台、台式计算机、大型机和超级计算机。

严格来讲，Linux这个词本身只表示Linux内核，但实际上人们已经习惯了用Linux来形容整个基于Linux内核，并且使用GNU 工程各种工具和数据库的操作系统。

Linux是一套使用和自由传播的类Unix操作系统，是一个基于POSIX和UNIX的多用户、多任务、支持多线程和多CPU的操作系统。

它能运行主要的UNIX工具软件、应用程序和网络协议。

它支持32位和64位硬件。

Linux继承了Unix以网络为核心的设计思想，是一个性能稳定的多用户网络操作系统。

linux的核心是的，自由使用的，核心源代码是开放的.而unix 的核心并不公开在对硬件的要求上，linux比unix要低，没有unix那么苛刻.在安装上linux比unix容易掌握.在使用上，linux相对没有unix那么复杂.Unix多数是硬件厂商针对自己的硬件平台的操作系统，主要与CPU等有关，如Sun 的Solaris作为商用，定位在其使用SPARC/SPARCII的CPU的工作站及服务器上，当然Solaris也有x86的版本，而Linux也有其于RISC 的版本。

至于价格，个人使用的Linux基本上算是的，不同的Linux发行厂商针对企业级应用在基本的系统上有些优化，如RedHat的Enterprise产品，这些产品包括支持服务是比较贵的。

像IBM/HP/SUN的Unix，因为主要是针对其硬件平台，所以操作系统通常在设备价格中。

(没有人单独去买一个Unix操作系统的) 在性能上，linux没有unix那么全面，但基本上对个人用户和小型应用来说是绰绰有余.通常情况下，如果你有机会使用到Unix环境，比如银行、电信部门，那一般都是固定机型的Unix。

linux毕业论文课题【摘要】随着计算机技术的不断发展，Linux操作系统越来越成为人们日常生活中必不可少的一部分。

本篇毕业论文主要研究了Linux操作系统的发展历程、特点以及其在不同领域中的应用，旨在探讨Linux操作系统的优点和不足，进一步促进其发展和应用。

【关键词】Linux操作系统；特点；应用；优点；不足一、绪论Linux操作系统是一种自由开源的操作系统，它是由芬兰的林纳斯·托瓦兹（Linus Torvalds）在1991年编写的，它的诞生标志着计算机技术的一个重要转折点。

Linux操作系统与微软Windows和苹果Mac OS是三大主流的操作系统之一，但它与其他两种操作系统有着本质上不同的特点和优点，如更加安全、可靠、高效等。

随着时间的不断推移，Linux操作系统的应用范围也不断扩大，其应用领域涵盖了各个方面，不仅在互联网领域、服务器领域、嵌入式领域等方面有很广泛的应用，也逐渐进入了桌面领域、移动终端领域等。

本篇毕业论文主要从Linux操作系统的发展历程、特点以及其在不同领域中的应用等方面进行探讨，重点研究Linux操作系统的优点和不足，旨在更好地促进Linux操作系统的发展和推广。

二、Linux操作系统的发展历程Linux操作系统的诞生可以追溯到20世纪90年代初期，当时的计算机技术一直被主流操作系统如Windows和Mac OS所主导。

但正是在这个时候，一位年仅21岁的芬兰学生Linus Torvalds开始了他的职业生涯，他在研究过程中发现自己需要一个方便的操作系统来进行工作，于是他开始了自己的创作之路，编写了一个简单的内核程序。

随着时间的推移，这个内核程序越来越完善，于是Linux操作系统诞生了。

在Linux操作系统的早期发展阶段，它的发展受到了很多的限制，如缺乏资金、人力、技术等方面的支持，使得Linux 操作系统的应用范围受到了一定的限制。

但是，正是这些“限制”促使了Linux操作系统自由、开放、共享的理念更加深入人心。

网上选课系统设计的关键技术及系统的构建外文翻译大学毕业论文英文文献翻译毕业设计（论文）外文文献翻译2017届文献、资料题目：网上选课系统设计的关键技术及系统的构建文献、资料来源：文献、资料发表（出版）日期：院（部）：专业：计算机科学与技术班级：姓名：学号：指导教师：翻译日期：2017.02.14网上选课系统设计的关键技术及系统的构建Key Techniques for Web Course-Choosing System Design andConstructionEric T. Freeman / Elisabeth RobsonO'Reilly Media,Nanyang 473004,China 2008-05, TP311.52.摘要学生选课是学分制管理制度改革的核心。

目前，各企业及高校已经研制出的网上选课系统，或因管理模式不同或因系统通用性不强，使得直接投入使用有相当大的困难，为适应南阳理工学院学分制管理制度的改革需要，自主研发了网上选课系统。

给出了网上选课系统设计的三个关键技术：面向对象、系统安全、数据优化，并利用JSP技术构建了网上选课系统，实现了数据录入、查询检索、报表统计等功能。

为整体认识和解决基于学分制网上选课系统的结构方案设计，解决设计中的各种实际问题提供了技术、方法和手段的支持，也为全面系统地实现学分制教学管理模式的构建奠定了基础。

关键词：Web course-choosing / system design / key techniques / construction 引言网上选课是学分制教学管理的重要组成部分，其特点可以概括为培养模式的多样性、学习内容的选择性、学习进程的自主性、学习时间与空间的灵活性等。

灵活性的大量增加严重冲击传统的教学管理模式，手工处理方式已不能适应新的管理模式，各高校都在探索研究适应新的教学管理模式的网上选课系统。

目前各高校自主研发的系统因紧密结合所在院校的教学管理模式，所以软件通用性不高，往往仅适用于所在高校。

我认识的linux（一）linux的基本知识学习linux，基本对linux有了一定的了解，为了更好的学习linux 基本操作，在pc机上装了虚拟机，我还借了张光盘装了linux，装了双系统，亲身体会linux操作。

了解到：Linux是目前全球对大的一个自由免费软件。

它本身是一个功能可与Unix和Windows相媲美的操作系统，具有完备的网络功能，它的用法与Unix非常相似，因此许多用户不在购买昂贵的Unix，转而投入到Linux免费系统的怀抱。

Linux最初由芬兰大学生Linus Torvalds开发，其源程序在Internet 网上公开发布，由此引起了全球电脑爱好者的开发热情，许多人下载源程序并按自己的意愿完善某一方面的功能，再发到网上，Linux因此也被雕刻成为全球最稳定、最有发展前景的操作系统。

Linux的特点：1.开放性开放性是指系统遵循世界标准规范，特别是遵循开放互联国际标准。

凡遵循国际标准所开发的硬件和软件，都能彼此兼容，可方便的实现互连。

2.多用户多用户是指系统资源可以被不同用户各自拥有，即每个用户对自己的资源有特定的权限，互不影响。

Linux和Unix都具有多用户的特性。

3.多任务Linux系统调度每一个进程，平等的访问微处理器。

由于CPU的处理速度非常的快，其结果是，启动的应用程序看起来好像在并行运行。

事实上，从处理器执行一个应用程序的一组指令到Linux调度微处理器再次运行这个程序之间只是很短的时间延迟，用户是感觉不出来的。

4.良好的用户界面Linux向用户提供了两种界面：用户界面和系统调用。

Linux的传统用户界面是基于文本的命令行界面，即shell，它既可以联机使用，又可存在文件上脱机使用。

Shell有很强的程序设计能力，用户可方便的用它编制程序，从而为用户扩充系统功能提供了更高级的手段。

系统调用是给用户提供编程使用的界面。

用户可以在编程时直接使用系统提供的调用命令，系统通过这个界面为用户程序提供低级、高效率的服务。

浅析信息时代的操作系统——Linux
刘雪飞
【期刊名称】《内江职业技术学院学报》
【年(卷),期】2008(002)003
【摘要】Linux是一种计算机操作系统，该操作系统的内核的名字也是“Linux”。

它是自由软件和开放源代码发展中最著名的例子。

本文主要论述了Linux的现状、特点、应用以及对未来软件业的影响。

【总页数】3页(P46-48)
【作者】刘雪飞
【作者单位】内江职业技术学院．四川内江611100
【正文语种】中文
【中图分类】TP316
【相关文献】
1.浅析嵌入式Linux操作系统的实时应用中的问题与优化 [J], 袁世军
2.浅析使用Linux操作系统完成小学计算机教育的可行性 [J], 吴佳骅
3.浅析Linux操作系统的基本配置 [J], 郝国良
4.浅析Linux操作系统的网络安全及防范策略 [J], 韩晓虹
5.Linux操作系统性能评测与测试指标浅析 [J], 周晓宇
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2011-2012学年第一学期 电信学院计算机系

LINUX系统调研报告

课设名称 系统管理与维护 班 级 学 号 姓 名 Linux操作系统常用命令详细介绍 一、 文件管理命令总结及用法： # ls ls -a 列出当前目录下的所有文件，包括以.头的隐含文件 ；# ls ls -l或ll 列出当前目录下文件的详细信息 ；文件管理 # pwd pwd 查看当前所在目录的绝对路经 ； # cd cd .. 回当前目录的上一级目录 ； # cd cd - 回上一次所在的目录 ； # cd cd ~ 或 cd 回当前用户的宿主目录 ； # cd cd ~用户名 回指定用户的宿主目录 ； # mkdir mkdir 目录名 创建一个目录 ； # mkdir mkdir –p 递归式去创建一些嵌套目录 ； # rmdir Rmdir 空目录名 删除一个空目录 ；# rm rm 文件名 文件名 删除一个文件或多个文件 ；# rm rm -rf 非空目录名 递归删除一个非空目录下的一切，不让提式-f ； # cat cat文件名 一屏查看文件内容 ； # more more文件名 分页查看文件内容 ； # less less 文件名 可控分页查看文件内容 ； # grep grep字符 文件名 根据字符匹配来查看文件部分内容 文件管理 ；# mv mv 路经/文件 /经/文件 移动相对路经下的文件到绝对路经下； # mv mv 文件名 新名称 在当前目录下改名 # cp cp /路经/文件 ./ 移动绝对路经下的文件到当前目录下 ； # find find 路经 -name “字符串” 查找路经所在范围内满足字符串匹配的文件和目录 ； # ln ln 源文件 链接名 创建当前目录源文件的硬链接 ln /home/test /usr/test1 在/usr下建立/home/test的硬链接 ； # ln Ln -s a b 创建当前目录下a的符号链接b ； # touch touch file1 file2 创建两个空文件 ； # df df 用于报告文件系统的总容量，使用量，剩余容量；# du du -b /home 查看目前/HOME目录的容量(k)及子目录的容量(k)；# fdisk fdisk -l 查看系统分区信息 ；# fdisk fdisk /dev/sdb 为一块新的SCSI硬盘进行分区 ；# mkfs.ext3 Mkfs.ext3 /dev/sdb1 为第一块SCSI硬盘的第一主分区格式化成 ext3的文件系统 mkfs.ext2 Mkfs.ext2/dev/sdb2 格式化成ext2文件系统 。 二、 磁盘管理命令及总结： # mount mount -t 文件系统类型 设备路经 访问路经 ；# 文件系统类型 Iso9660 光驱文件系统 vfat Fat文件系统(windows) ；# Umount /mnt/cdrom 卸载/mnt/cdrom为空 三、 挂载光驱命令及总结： # mount –t iso9660 /dev/cdrom /mnt/cdrom 挂载FAT # mount –t vfat /dev/hda5 /mnt/cdrom 挂第一个ide的第五个逻辑分区 四、 文件权限命令及总结： # chmod chmod u+s file 为file的属主加上特殊权限 ；chmod g+r file 为file的属组加上读权限 ；chmod o+w file 为file的其它用户加上写权限 ；chmod a-x file 为file的所有用户减去执行权限 ；chmod 765 file 为file的属主设为完全权限，属组设成读写权，其它用户具有读和执心权限；# chown chown root /home 把/home的属主改成root用户 ；# chgrp chgrp root /home 把/home的属组改成root组。 五、 打印管理命令及总结： # redhat-config-printer-tui 进入安装打印机界面 ；# lp lp –d hptr file 打印file到hptr的打印机上；# lpq Lpq –P 打印机名 查看打印机的状态 ；# lprm Lprm –P 打印机名 a 删除打印机内的打印作业 ；# disable Disable –r “changing paper” HPtr 禁用打印机并提示原因 ；# enable Enable HPtr 重新启用被禁用的 。 六、 用户管理命令及总结： # useradd Useradd 创建一个新的用户 ；# groupadd Groupadd 组名 创建一个新的组 ；# passwd Passwd 用户名 为用户创建密码 ；# Passwd -d Passwd -d用户名 删除用户密码也能登陆 ；# Passwd -l Passwd -l用户名 锁定账号密码 ；# Passwd -u Passwd -u用户名 解锁账号密码 ；# Passwd -S Passwd -S用户名 查询账号密码 ；# Usermod -l Usermod -l 新用户名 老用户名 为用户改名 ；# Usermod -L Usermod -L 要锁定用户名 锁定用户登陆 ；# Usermod -U Usermod –U解锁用户名 解锁用户登陆 ；# Usermod -u Usermod –u 501用户名 改变用户UID ；# Userdel Userdel–r 用户名 删除用户一切 ；# Groupmod -n Groupmod –n新用户名 老用户名 为组改名 ；# Groupmod -g Groupmod –g 501 组名 改变组GID ；# groupdel Groupdel组名 先应删它的用户 删除组 ；# gpasswd -a gpasswd -a 用户名 组名 增加用户到组 ；# Id id 用户名 查用户信息 。 七、 软件管理命令及总结： # rpm -qa rpm –qa | less 查询已安装RPM ；# rpm –qa | grep ftp 查询指定RPM ；# rpm -q rpm -q 已安装的RPM包 查是否安装 ；# rpm -q telnet-server 查看telnet服务器包 ；# rpm -qi rpm –qi 软件包名称 查看软件的描述信息 ；# rpm -ql rpm –ql软件包名称 查询软件包的文件列表 ；# rpm -qf rpm –qf软件包名称 查询某个文件所属的软件包 ；# rpm -qp rpm –qp软件包全名 查询未安装的软件包信息 ；# rpm -e rpm –e 软件包名称 删除具体的软件包 ；# rpm -U rpm –Uvh软件包全名 升级软件包并显示过程 ；# rpm -ivh rpm –ivh 软件包全名 安装软件包并显示过程 ；# rpm -V rpm –V软件包名称 验证软件包的大小，类型等 ；# tar -c 创建包 –x 释放包 -v 显示命令过程 –z 代表压缩包 ；# tar -cf tar –cvf benet.tar /home/benet 把/home/benet目录打包 ；# tar -czf tar –zcvf benet.tar.gz /mnt 把目录打包并压缩 ；# tar –tf tar –tf benet.tar 看非压缩包的文件列表 ；# tar –tzf tar –tf benet.tar.gz 看压缩包的文件列表 ；# tar –xf tar –xf benet.tar 非压缩包的文件恢复 ；# tar –zxvf tar –zxvf benet.tar.gz 压缩包的文件解压恢复 ；# tar -jxvf tar –jxvf benet.tar.bz2 ；# diff diff file1 file2 > 补丁名.patch 为新旧文件生成补丁文件 ；# diff diff file1 file2 比较两个文件的区别 ；# Patch Patch file补丁名.patch 打补丁 ；# ./configure –prefix=/usr/local/ 编译前配置 ；# make 编译 ；# make install 安装编译好的源码包 。 八、 启动管理命令及总结： # reboot Init 6 重启LINUX系统 ；# Halt Init 0 Shutdown –h now 关闭LINUX系统 ；# runlevel 显示系统运行级 ；# Init [0123456] 改变系统运行级,7种 ；# Chkconfig –-list [服务名称] 查看服务的状态 ；# Chkconfig –-level on|off|set 设置服务的启动状态 ；# Chkconfig on|off|set 设置非独立服务启状态 ；# Top动态 Ps-aux静态 进程树pstree 查看系统进程 ；# 程序名 & 后台运行程序 ；# fg 把后台运行的进程调回前台 。 九、 进程管理命令及总结： # bg 把前台运行进程调到后台 ；# renice Renice +1 180 把180号进程的优先级加1； # kill Kill PID 终止某个PID进程 ；# at at 5pm + 3 days /bin/ls 指定三天后下午5:00执行/bin/ls ；# crontab Crontab -e 用VI的形式来编辑自动周期性任务 ；# crontab Crontab -l 查看自动周期性任务 ；# crontab Crontab -r 删除自动周期性任务 # crond Service crond 。

班级：09501班******学号：*********** 院系：信息工程学院Linux操作系统摘要：操作系统（Operating System，简称OS）传统上是负责对计算机硬件直接控制及管理的系统软件。

操作系统的功能一般包括处理器管理、存储管理、文件管理、设备管理和作业管理等。

当多个程序同时运行时，操作系统负责规划以优化每个程序的处理时间。

计算机操作系统中DOS、windows(包括2000、XP、VISTA.WIN7）、UNIX、LINUX 比较常见。

本学期我们主要学习了Linux，本文主要对Linux操作系统的版本及特点、Linux与Windows的主要区别、Linux的简单操作、Linux与外围设备的连接以及Linux新的发展基础进行了简单的分析和阐述。

关键词：Linux操作系统、版本特点、主要区别、简单操作、发展一、Linux操作系统的版本及特点发行版为许多不同的目的而制作, 包括对不同计算机结构的支持, 对一个具体区域或语言的本地化，实时应用，和嵌入式系统，甚至许多版本故意地只加入免费软件。

目前，超过三百个发行版被积极的开发，最普遍被使用的发行版有大约十二个。

Linux的发行版本可以大体分为两类，一类是商业公司维护的发行版本，一类是社区组织维护的发行版本，前者以著名的Redhat（RHEL）为代表，后者以Debian为代表。

RedhaRedhat，应该称为Redhat系列，包括RHEL(Redhat Enterprise Linux，也就是所谓的Redhat Advance Server，收费版本)、Fedora Core(由原来的Redhat桌面版本发展而来，免费版本)、CentOS(RHEL的社区克隆版本，免费)。

Redhat应该说是在国内使用人群最多的Linux版本，甚至有人将Redhat等同于Linux，而有些老鸟更是只用这一个版本的Linux。

所以这个版本的特点就是使用人群数量大，资料非常多，言下之意就是如果你有什么不明白的地方，很容易找到人来问，而且网上的一般Linux教程都是以Redhat为例来讲解的。

目录前言 (1)1Linux的简介 (2)1.1什么是Linux (2)1.2Linux系统的主要特点 (2)1.3LINUX的组成 (3)2基本的网络命令以及他们的使用方法 (3)2.1ping命令 (3)2.2ifconfig命令 (4)2.3netstat命令 (4)2.4echo命令 (5)3网络配置文件的配置方法 (6)4telnet配置 (7)4.1telnet简介 (7)4.2telnet建立账户 (7)4.3telnet测试账户 (8)5配置NFS服务器 (9)5.1NFS简介 (9)5.2NFS的文件远程挂载 (10)6配置samba服务器 (11)6.1samba服务器的简介 (12)6.2samba服务器文件共享 (12)7简单shell编程 (13)7.1编写shell脚本 (13)7.2编写弹出式菜单的shell程序 (14)7.3编写一个小九九乘法表 (16)8gcc的简单使用 (17)8.1递归的方法求N的阶乘 (17)8.2求1至n之间的奇数 (18)8.3求1至n的累加和 (19)总结 (21)前言Linux系统是一种自由和开放源码的类Unix操作系统。

目前存在着许多不同的Linux,但它们都使用了Linux内核。

Linux可安装在各种计算机硬件设备中，从手机、平板电脑、路由器和视频游戏控制台，到台式计算机、大型机和超级计算机。

Linux是一个领先的操作系统，世界上运算最快的10台超级计算机运行的都是Linux操作系统。

严格来讲，Linux这个词本身只表示Linux内核，但实际上人们已经习惯了用Linux来形容整个基于Linux内核，并且使用GNU 工程各种工具和数据库的操作系统。

Linux得名于计算机业余爱好者Linus Torvalds。

Linux凭借其自由、免费、开放源代码的优势，经过来自互联网、遍布全球的程序员的努力，再加上IBM、Sun等计算机巨头的支持，Linux在手机操作系统市场中异军突起，尤其是在众多知名厂商宣布支持Linux手机操作系统之后，Linux 的发展将不容忽视。

Linux网络操作系统简介Linux网络操作系统是一种基于Linux内核的操作系统，专门用于网络设备的管理和控制。

它提供了强大的网络功能和灵活的可定制性，使得网络设备能够实现高效的数据传输和管理。

本文将介绍Linux网络操作系统的特点、优势以及应用场景。

特点开源性Linux网络操作系统是开源的，使用GNU通用公共许可证（GPL）等开源协议发布，任何人都可以查看、修改和分发源代码。

这使得开发者能够根据自身需求进行二次开发和定制，以适应不同的网络设备和应用场景。

稳定可靠Linux内核作为其基础，保证了Linux网络操作系统的稳定性和可靠性。

由于其广泛的应用和社区支持，用户可以快速获取补丁和更新，从而解决潜在的问题和漏洞。

强大的网络功能Linux网络操作系统提供了丰富的网络功能，包括路由、防火墙、负载均衡、VPN、虚拟化等。

它支持多种网络协议和技术，如IPv4、IPv6、BGP、OSPF、VLAN、VXLAN等，能够满足各种网络场景的需求。

可扩展性和灵活性Linux网络操作系统的架构设计考虑到了可扩展性和灵活性。

它支持模块化的设计，可以根据需求加载和卸载不同的模块，从而实现功能的扩展和定制。

高度可定制化由于开源的特性，用户可以根据自身需求进行定制和开发。

Linux网络操作系统提供了丰富的工具和API，使得开发者能够自定义网络功能和应用，并且与其他系统进行集成。

优势成本效益Linux网络操作系统是免费开源的，相比于商业网络操作系统，它不需要支付额外的许可费用。

这使得它成为中小型企业和个人用户的首选，能够以更低的成本建立和管理网络设备。

社区支持Linux网络操作系统有一个庞大的开源社区，用户可以在社区中获取帮助、交流经验和分享资源。

这个社区不断更新和完善着操作系统的功能和性能，为用户提供了更好的使用体验。

丰富的应用生态由于其开放性和通用性，Linux网络操作系统拥有丰富的应用生态系统。

用户可以选择各种第三方工具和应用来满足自己的需求，而不局限于特定厂商或生态系统。

文件系统的概述：由于每个操作系统对于文件的描述方式不一致，通常描述一个文件的信息（权限、拥有者、时间等）有一个专有的名词叫做“元数据”，为了能够让操作系统管理存储在磁盘上的文件，需要对磁盘做一个格式化的操作，格式化操作会为某个磁盘/分区来部署一个文件系统，然后操作系统就可以通过文件系统来管理存储在磁盘上的文件了。

LinuxRPM、YUM的概念和操作及进程管理的概念及管理命令RPM即Red-Hat Package Manager●由Red Hat公司提出，被众多Linux发行版所采用●建立统一的数据库文件●详细记录软件包安装、卸载等变化信息●自动分析软件包依赖关系Yum（全称为 Yellow dog Updater,Modified）是一个在Fedora和RedHat以及CentOS中的Shell前端软件包管理器。

基于RP M包管理，能够从指定的服务器自动下载RPM包并且安装，可以自动处理依赖性关系，并且一次安装所有依赖的软件包，无须繁琐地一次次下载、安装。

rpm的简单查询指令·查询已安装的rpm列表：rpm -qa|grep xxrpm包名基本格式查询返回的结果为一个rpm包名：firefox-78.6.0-1.el7.centos.x86_64名称：firefox版本号：78.6.0-1适用操作系统：el7.centos.x86_64表示centos 7.x的64位操作系统如果是i686、i386表示32位操作系统，noarch表示通用基本指令·查询yum服务器是否有需要安装的软件o yum list|grep xx 软件列表·安装指定的yum包o yum install xxx 下载安装进程的基本介绍1）在 Linux 中，每个执行的程序（代码）都称为一个进程。

每一个进程都分配一个ID 号。

（2）每一个进程，都会对应一个父进程，而这个父进程可以复制多个子进程。

例如www 服务器。

Web Server for Embedded SystemsAfter the “everybody-in-the-Internet-wave” now obviously follows the“everything-in-the-Internet-wave”.The most coffee, vending and washingmachines are still not available about the worldwide net. However the embeddedInternet integration for remote maintenance and diagnostic as well as the so-calledM2M communication is growing with a considerable speed rate.Just the remote maintenance and diagnostic of components and systems by Webbrowsers via the Internet, or a local Intranet has a very high weight for manydevelopment projects. In numerous development departments people work oncompletely Web based configurations and services for embedded systems. Theremaining days of the classic user interface made by a small LC-display with frontpanel and a few function keys are over. Through future evolutions in the field ofthe mobile Internet, Bluetooth-based PAN s (Personal Area Network's) andthe rapidly growing M2M communication (M2M=Machine-to-Machine)a further innovating advance is to be expected.The central function unit to get access on an embedded system via Web browser isthe Web server. Such Web servers bring the desired HTML pages (HTML=HyperText Markup Language) and pictures over the worldwide Internetor a local network to the Web browser. This happens HTTP-based (HyperText Transfer Protocol). A TCP/IP protocol stack –that means it is based onsophisticated and established standards–manages the entire communication.Web server (HTTP server) and browser (HTTP client) build TCP/IP-applications. HTTP achieved a phenomenal distribution in the last years.Meanwhile millions of user around the world surf HTTP-based in the WorldWide Web. Today almost every personal computer offers the necessaryassistance for this protocol. This status is valid more and more for embeddedsystems also. The HTTP spreads up with a fast rate too.1. TCP/IP-based HTTP as Communication PlatformHTTP is a simple protocol that is based on a TCP/IP protocol stack (picture 1.A).HTTP uses TCP (Transmission Control Protocol). TCP is a relative complex andhigh-quality protocol to transfer data by the subordinate IP protocol. TCP itselfalways guarantees a safeguarded connection between two communication partnersbased on an extensive three-way-handshake procedure. As aresult the data transfer via HTTP is always protected. Due tothe extensive TCP protocol mechanisms HTTP offers only a low-gradeperformance.Figure 1: TCP/IP stack and HTTP programming modelHTTP is based on a simple client/server-concept. HTTP server and clientcommunicate via a TCP connection. As default TCP port value the port number80 will be used. The server works completely passive. He waits for a request(order) of a client. This request normally refers to the transmition of specificHTML documents. This HTML documents possibly have to be generateddynamically by CGI. As result of the requests, the server will answer with aresponse that usually contains the desired HTML documents among others(picture 1.B).GET /test.htm HTTP/1.1Accept]: image/gif, image/jpeg, */*User selling agent: Mozilla/4.0Host: 192.168.0.1Listing 1.A: HTTP GET-requestHTTP/1.1 200 OKDate: Mon, 06 Dec 1999 20:55:12 GMTServer: Apache/1.3.6 (Linux)Content-length: 82Content-type: text/html<html><head><title>Test-Seite</title></head><body>Test-SeiteThe DIL/NetPCs DNP/1110 – Using the Embedded Linux</body></html>Listing 1.B: HTTP response as result of the GET-request from listing 1.AHTTP requests normally consist of several text lines, which are transmitted to theserver by TCP. The listing 1.A shows an example. The first line characterizes therequest type (GET), the requested object (/test1.htm) and the used HTTP version(HTTP/1.1). In the second request line the client tells the server, which kind offiles it is able to evaluate. The third line includes information about theclient- software. The fourth and last line of the request from listing 1.A is used toinform the server about the IP address of the client. In according to the type ofrequest and the used client software there could follow some further lines. Asan end of the request a blank line is expected.The HTTP responses as request answer mostly consist of two parts. At first thereis a header of individual lines of text. Then follows a content object (optional).This content object maybe consists of some text lines –in case of a HTML file– ora binary file when a GIF or JPEG image should be transferred. The first line of theheader is especially important. It works as status or error message. If anerror occurs, only the header or a part of it will be transmitted as answer.2. Functional principle of a Web ServerSimplified a Web server can be imagined like a special kind of a file server.Picture 2.A shows an overview. The Web server receives a HTTP GET-requestfrom the Web browser. By this request, a specific file is required as answer (seestep 1 into picture 2.A). After that, the Web server tries to get access on the filesystem of the requested computer. Then it attempts to find the desired file (step 2).After the successful search the Web server read the entire file(step 3) and transmit it as an answer (HTTP response comprising of headerand content object) to the Web browser (step 4). If the Web server cannot findthe appropriate file in the file system, an error message (HTTP response whichonly contains the header) is simply be send as response to the client.Figure 2: Functional principle from Web server and browserThe web content is build by individual files. The base is build by static files withHTML pages. Within such HTML files there are references to further filesembedded –these files are typically pictures in GIF or JPEG format. However,also references to other objects, for example Java-Applets, are possible. After aWeb browser has received a HTML file of a Web server, this file will beevaluated and then searched for external references. Now the steps 1 to 4 frompicture 2.A will run again for every external reference in order to request therespective file from the corresponding Web server. Please note, that such areference consists of the name or IP address of a Web server (e.g. ""),as well as the name of the desired file (e.g. "picture1.gif"). So virtually everyreference can refer to another Web server. In other words, a HTML file could belocated on the server "ssv-embedded.de" but the required picture -which isexternal referenced by this HTML file- is located on the Web server"". Finally this (worldwide) networking of separate objects is thecause for the name World Wide Web (WWW). All files, which are required by aWeb server, are requested from a browser like the procedure shown on picture2.A. Normally these files are stored in the file system of the server. TheWebmaster has to update these files from time to time.A further elementary functionality of a Web server is the CommonGateway Interface(CGI) -we have mentioned before. Originally this technologyis made only for simple forms, which are embedded into HTML pages. The data,resulting from the padding of a form, will be transmitted to a Web server viaHTTP-GET or POST-request (see step 1 into picture 2.B). In such a GET- orPOST-request the name of the CGI program, which is needed for theevaluation of a form, is fundamentally included. This program has to be on theWeb server. Normally the directory "/cgi-bin" is used as storage location.As result of the GET- or POST-request the Web server starts the CGI programlocated in the subdirectory "/cgi-bin" and delivers the received data in form ofparameters (step 2). The outputs of a CGI program are guided to the Web server(step 3). Then the Web server sends them all as responses to the Web browser(step 4).3. Dynamic generated HTML PagesIn contradiction to a company Web site server, which informs people about theproduct program and services by static pages and pictures, an embeddedWeb server has to supply dynamically generated contents. The embedded Webserver will generate the dynamic pages in the moment of the first access by abrowser. How else could we check the actual temperature of a system viaInternet? Static HTML files are not interesting for an embedded Web server.The most information about the firmware version and service instructions arestored in HTML format. All other tasks are normally made via dynamic generatedHTML.There are two different technologies to generate a specific HTML page in themoment of the request: First the so-called server-side-scripting and secondthe CGI programming. At the server-side-scripting, script code is embeddedinto a HTML page. If required, this code will be carried out on the server (server-sided).For this, there are numerous script languages available. All these languages areusable inside a HTML-page. In the Linux community PHP is used mostly. Thefavourite of Microsoft is VBScript. It is also possible to insert Java directly intoHTML pages. Sun has named this technology JSP(Java Server Pages).The HTML page with the script code is statically stored in the file system of theWeb server. Before this server file is delivered to the client, a special programreplaces the entire script code with dynamic generated standard HTML. The Webbrowser will not see anything from the script language.Figure 3: Single steps of the Server-Side-ScriptingPicture 3 shows the single steps of the server-side-scripting. In step 1 the Webbrowser requests a specific HTML file via HTTP GET-request. The Web serverrecognizes the specific extension of the desired file (for example *.ASP or *.PHPinstead of *.HTM and/or *.HTML) and starts a so-called scripting engine(see step 2). This program gets the desired HTML file including the script codefrom the file system (step 3), carry out the script code and make a newHTML file without script code (step 4). The included script code will be replacedby dynamic generated HTML. This new HTML file will be read by the Webserver (step 5) and send to the Web browser (step 6). If a server-sided scripting issupposed to be used by an embedded Web server, so you haveto consider the necessary additional resources. A simple example: In orderto carry out the embedded PHP code into a HTML page, additional programmodules are necessary for the server. A scripting engine together with theembedded Web server has to be stored in the Flash memory chip of an embeddedsystem. Through that, during run time more main memory is required.4. Web Server running under LinuxOnce spoken about Web servers in connection with Linux most peopleimmediately think of Apache. After investigations of the Netcraft Surveythis program is the mostly used Web server worldwide. Apache is anenhancement of the legendary NCSA server. The name Apache itself hasnothing to do with Red Indians. It is a construct from "A Patchy Server" becausethe first version was put together from different code and patch files.Moreover there are numerous other Web servers - even for Linux. Most of this arestanding under the GPL (like Apache) and can be used license free. Avery extensive overview you can find at "/". EveryWeb server has his advantages and disadvantages. Some are developed forspecific functions and have very special qualities. Other distinguishes at bestthrough their reaction rate at many simultaneous requests, as wellas the variety of theirconfiguration settings. Others are designed to need minimal resources and offer very small setting possibilities, as well as only one connection to a client.The most important thing by an embedded Web server is the actual resource requirements. Sometimes embedded systems offer only minimal resources, which mostly has to be shared with Linux. Meanwhile there are numerous high- performance 32-bit-386/486-microcontroller or (Strong)ARM-based embedded systems that own just 8 Mbytes RAM and 2 Mbytes Flash-ROM (picture 4). Outgoing from this ROM (Read-only-Memory, i.e. Flash memory chips) a complete Linux, based on a 2.2- or 2.4-Kernel with TCP/IP protocol stack and Web server, will be booted. HTML pages and programs are also stored in the ROM to generate the dynamic Web pages. The space requirements of an embedded system are similar to a little bigger stamp. There it is quite understandable that there is no place for a powerful Web server like Apache.Figure 4: Embedded Web Server Module with StrongARM and LinuxBut also the capability of an Apache is not needed to visualize the counter of a photocopier or the status of a percolator by Web servers and browsers. In most cases a single Web server is quite enough. Two of such representatives are boa () and thttpd (). At first, both Web servers are used in connection with embedded systems running under Linux. The configuration settings for boa and thttpd are poor, but quite enough. By the way, the source code is available to the customer. The practicable binary files for these servers are always smaller than 80 Kbytes and can be integrated in the most embedded systems without problems. For the dynamic generation of HTML pages both servers only offer CGI (Common Gateway Interface) as enlargement. Further technologies, like server-side-includes (SSI) are not available.The great difference between an embedded Web server and Apache is, next to the limited configuration settings, the maximal possible number of simultaneous requests. High performance servers like Apache immediately make an own process for every incoming call request of a client. Inside of this process allfurther steps will then be executed. This requires a very good programming and a lot of free memory resources during run time. But, on the other hand many Web browsers can access such a Web server simultaneously. Embedded Web server like boa and thttpd work only with one single process. If two users need to get access onto a embedded Web server simultaneously, one of both have to wait a few fractions of a second. But in the environment of the embedded systems that is absolutely justifiable. In this case it is first of all a question of remote maintenance, remote configuration and similar tasks. There are not many simultaneous requests expected.The DIL/NetPCs DNP/1110 – Using the Embedded LinuxList of FiguresFigure 1: TCP/IP stack and HTTP programming modelFigure 2: Functional principle from Web server and browserFigure 3: Single steps of the Server-Side-ScriptingFigure 4: Embedded Web Server Module with StrongARM and LinuxListingsListing 1.A: HTTP GET-requestListing 1.B: HTTP response as result of the GET-request from listing 1.A ContactSSV Embedded SystemsHeisterbergallee 72D-30453 HannoverTel. +49-(0)511-40000-0Fax. +49-(0)511-40000-40Email: sales@ist1.deWeb: www.ssv-embedded.deDocument History (Sadnp05.Doc)Revision Date Name1.00 24.05.2002FirstVersion KDWThis document is meant only for the internal application. The contents ofthis document can change any time without announcement. There is takenover no guarantee for the accuracy of the statements. Copyright ©SSV EMBEDDED SYSTEMS 2002. All rights reserved.INFORMATION PROVIDED IN THIS DOCUMENT IS PROVIDED 'ASIS' WITHOUT WARRANTY OF ANY KIND. The user assumes the entirerisk as to the accuracy and the use of this document. Some names withinthis document can be trademarks of their respective holders.北京工业大学毕业设计（译文）译文：嵌入式系统的网络服务器在“每个人都处在互联网的浪潮中”之后，现在很明显随之而来的是“每件事都处在互联网的浪潮中”。

linux操作系统论文Linux操作系统论文一、引言1.1 研究背景1.2 研究目的1.3 研究方法二、Linux操作系统概述2.1 Linux的起源与发展2.2 Linux的特点与优势2.3 Linux的应用领域三、Linux操作系统架构3.1 内核3.1.1 内核的组成与功能3.1.2 内核的模块化设计3.1.3 内核的版本管理3.2 Shell3.2.1 Shell的概念与作用3.2.2 常用的Shell解释器 3.2.3 Shell脚本编程基础3.3 文件系统3.3.1 文件系统的概念与作用 3.3.2 常见的Linux文件系统 3.3.3 文件系统的管理与维护 3.4 进程管理3.4.1 进程的概念与特征3.4.2 进程的创建与调度3.4.3 进程的管理与监控3.5 网络服务3.5.1 Linux网络配置3.5.2 常见的Linux网络服务3.5.3 网络安全与防火墙配置四、Linux操作系统的安全性4.1 用户认证与权限管理4.1.1 用户账号的管理4.1.2 Linux权限模型4.1.3 权限管理工具与技巧4.2 系统安全性规范4.2.1 安全策略与规范4.2.2 安全漏洞的评估与修复 4.2.3 安全审计与监控4.3 数据加密与网络安全4.3.1 数据加密的基本原理4.3.2 Linux下的加密工具4.3.3 网络安全与攻防技术五、Linux操作系统的性能优化5.1 系统资源的管理与优化5.1.1 CPU的优化与使用率监控 5.1.2 内存的优化与使用率监控 5.1.3 硬盘的优化与使用率监控 5.2 进程与服务的优化5.2.1 进程的调度策略与优化5.2.2 服务的启动与优化5.2.3 网络性能的优化与监控六、Linux操作系统的应用案例6.1 云计算与虚拟化6.1.1 Linux在云计算中的应用6.1.2 Linux下的虚拟化技术6.2 大数据与6.2.1 Linux在大数据领域的应用 6.2.2 Linux与的结合6.3 嵌入式系统与物联网6.3.1 Linux在嵌入式系统中的应用6.3.2 Linux在物联网中的应用七、结论7.1 研究工作总结7.2 研究成果与展望附录：附件一、Linux操作系统安装指南附件二、Linux命令手册附件三、实验数据与分析结果法律名词及注释：1、版权：指作品的创作者在法律上享有的权利，包括署名权、署名许可权、发表权、修改权等。

shell 是一个命令语言解释器，它拥有自己内建的 shell 命令集，s hell 也能被系统中其 他应用程序所调用。用户在提示符下输入的命令都由 s hell 先解释然后传给 Linux 核心。
-1-
shell 的种类：sh；csh；ksh、tcsh、bash；在 Linux 中常用的 shell 是 bash，其次是 csh。 shell 命令的基本格式是： 命令名 [选项] <参数 1> <参数 2> „„ 我们学习的 shell 基本命令包括开关机指令（shutdown、halt）、登录和退出（login、logout、 exit、su、who）、修改属性（chmod、chown、chgrp）、创建目录（mkdir）、删除目录（rmdir）、 显示路径（pwd）、文件查看和连接命令（cat）、查看目录（ls）、复制命令（cp）、切换目录 （cd）、移动和重命名（mv）等；在学习过程中，需要上机反复联系才能熟练掌握基本命令 的使用，为后续工作打下坚实的基础。
4、文件系统管理
Linux 操作系统中，以文件来表示所有的逻辑实体与非逻辑实体。逻辑实体系指文件与 目录；非逻辑实体则泛指硬盘、终端机、打印机等。
Linux 文件系统中，结构上以 root file system 位于文件系统的最顶层。 root file system 开机时将 root partition 挂载在 / 的目录，若无法 mount / ，则开机时，不能进入 Linux 系统
Unix/Linux 程序设计 结课论文
通过两个月的课程学习，对与 Linux 有了一个基本的认识和了解，通过上机操作熟悉和 掌握了 Linux 的常用 shell 命令，学会了使用 vi 编辑器编写文件，了解了 Linux 系统的硬件 管理和网络指令，深入认识了 Linux 的文件管理系统和用户管理命令，学习了其文件系统的 压缩和备份以及在 Linux 操纵系统环境下的程序设计。

毕业设计（论文）题目: 浅谈linux操作系统的安全姓名学号专业系部指导教师目录第一章Linux操作系统概述 (1)1.1 Linux发展历史 (1)1.1.1 Linux的诞生和发展 (2)1.1.2 Linux名称的由来 (2)1.2 Linux的发展要素 (3)1.2.1 UNIX操作系统 (3)1.2.2 Minix操作系统 (4)1.2.3 POSIX 标准 (4)1.3 操作系统类型选择和内核版本的选择 (4)1.3.1 常见的不同公司发行的Linux异同 (5)1.3.2内核版本的选择 (9)1.4 Linux的系统架构 (10)1.4.1 Linux内核的主要模块 (10)1.4.2 Linux的文件结构 (12)1.5 GNU通用公共许可证 (13)第二章Linux与其他操作系统的比较 (15)2.1 Linux与UNIX的异同 (15)2.2 Linux和Windows的区别以及安全性的比较 (16)2.3 Linux与其他操作系统的区别 (18)2.4 Linux与其他系统的总体比较总结 (119)2.5 Linux与Windows根本比较—内核 (21)2.6 Linux的特性 (23)2.7 Linux与其他操作系统的区别 (25)第三章Linux的安全性能分析以及增强 (27)3.1 嵌入式Linux 的特点 (27)3.2 嵌入式Linux 现有安全机制及分析 (29)3.3 嵌入式Linux 安全缺陷 (31)3.4 小结 (33)结束语 (34)参考文献 (37)附录 (38)第一章Linux操作系统概述Linux系统是一个类似UNIX的操作系统，Linux系统是UNIX在微机上的完整实现。

UNIX操作系统是1969年由Ken Thompson 和Dennis Ritchie在美国贝尔实验室开发的一种操作系统。

由于其良好而稳定的性能迅速在计算机中得到广泛的应用，在随后几十年中也有了不断的改进。

关于Linux操作系统设计研究毕业论文目录中文摘要 (1)ABSTRACT (2)第1章 Linux概述 (3)1.1 Linux操作系统的诞生和发行版 (3)1.1.1 Linux系统的诞生 (3)1.1.2 Linux 发行版 (3)1.2 Linux应用和特性 (4)1.2.1 linux 的应用 (4)1.2.2 linux 的特性 (4)第2章 Tiny210开发板 (6)2.1 Tiny210 简介 (6)2.2 Tiny210硬件配置 (6)2.3 软件支持 (7)第3章移植前准备 (8)3.1软件平台的搭建 (8)3.1.1 虚拟机的安装 (8)3.1.2 Red Hat linux 的安装 (8)3.1.3 软件包和源码包的准备和下载 (8)第4章 Linux 核 (9)第5章 RTC芯片 (10)5.1 RTC芯片简述 (10)5.2I2C总线简介 (10)第6章字符设备驱动相关知识 (11)6.1 模块机制 (11)6.2 字符设备开发基本步骤 (12)6.3 主设备号和次设备号 (12)6.4 实现字符驱动程序 (13)第7章 RTC驱动实现 (16)7.1 设计思路 (16)7.2 RTC程序实现 (16)7.2.1 RTC基本数据结构 (16)7.2.2注册字符设备 (16)7.2.3 定义操作函数 (17)7.2.4 函数声明 (18)7.3 编译生成.ko文件 (18)7.4 实际运行及结果 (18)第8章结论 (20)谢辞 (21)参考文献 (22)附录A RTC驱动程序 (23)附录B Makefile文件 (41)附录C 应用层测试程序 (41)第1章 Linux概述1.1 Linux操作系统的诞生和发行版1.1.1 Linux系统的诞生1981年IBM推出了微型计算机IBM PC。

在它推出的前10年，MS-DOS操作系统主宰了整个计算机操作系统界。

而在当时，计算机硬件的价格在不断下跌，但软件仍处于高位。

摘自：《Linux企业集群》(The Linux Enterprise Cluster)英文原文:The Linux Enterprise ClusterOverviewThis chapter will introduce the cluster load-balancing software called IP Virtual Server (IPVS). The IPVS software is a collection of kernel patches that were merged into the stock version of the Linux kernel starting with version 2.4.23. When combined with the kernel's routing and packet-filtering capabilities (discussed in Chapter 2) the IPVS-enabled kernel lets you turn any computer running Linux into a cluster load balancer. Together, the IPVS-enabled cluster load balancer and the cluster nodes are called a Linux Virtual Server (LVS).The LVS cluster load balancer accepts all incoming client computer requests for services and decides which cluster node should reply to each request. The load balancer is sometimes called an LVS Director or simply a Director. In this book the terms LVS Director, Director, and load balancer all refer to the same thing.The nodes inside an LVS cluster are called real servers, and the computers that connect to the cluster to request its services are called client computers. The client computers, the Director, and the real servers communicate with each other using IP addresses the same way computers have always exchanged packets over a network; however, to make it easier to discuss this network communication, the LVS community has developed a naming convention to describe each type of IP address based on its role in the network conversation. So before we consider the different types of LVS clusters and the choices you have for distributing your workload across the cluster nodes (called scheduling methods), let's look at this naming convention and see how it helps describe the LVS cluster.LVS IP Address Name ConventionsIn an LVS cluster, we cannot refer to network addresses as simply "IP addresses." Instead, we must distinguish between different types of IP addresses based on the roles of the nodes inside the cluster. Here are four basic types of IP addressesused in a cluster:Virtual IP (VIP) addressThe IP address the Director uses to offer services to client computersReal IP (RIP) addressThe IP address used on the cluster nodesDirector's IP (DIP) addressThe IP address the Director uses to connect to the D/RIP networkClient computer's IP (CIP) addressThe IP address assigned to a client computer that it uses as a source IP address for requests sent to the clusterThe Virtual IP (VIP)The IP address that client computers use to connect to the services offered by the cluster are called virtual IP addresses (VIPs). VIPs are IP aliases or secondary IP addresses on the NIC that connects the Director to the normal, public network.[1] The LVS VIP is important because it is the address that client computers will use when they connect to the cluster. Client computers send packets from their IP address to the VIP address to access cluster services. You tell the client computers the VIP address using a naming service (such as DNS, DDNS, WINS, LDAP, or NIS), and this is the only name or address that client computers ever need to know in order to use the services inside the cluster. (The remaining IP addresses inside the cluster are not known to the client computer.)A single Director can have multiple VIPs offering different services to client computers, and the VIPs can be public IP addresses that can be routed on the Internet, though this is not required. What is required, however, is that the client computers be able to access the VIP or VIPs of the cluster. (As we'll see later, an LVS-NAT cluster can use a private intranet IP address for the nodes inside the cluster, even though the VIP on the Director is a public Internet IP address.)The Real IP (RIP)In LVS terms, a node offering services to the outside world is called a real server. (We will use the terms cluster node and real server interchangeably throughout thisbook.) The IP address used on the real server is therefore called a real IP address (RIP).The RIP address is the IP address that is permanently assigned to the NIC that connects the real server to the same network as the Director. We'll call this network cluster network or the Director/real-server network (D/RIP network). The Director uses the RIP address for normal network communication with the real servers on the D/RIP network, but only the Director needs to know how to talk to this IP address. The Director's IP (DIP)The Director's IP (DIP) address is used on the NIC that connects the Director to the D/RIP network. As requests for cluster services are received on the Director's VIP, they are forwarded out the DIP to reach a cluster node. As is discussed in Chapter 15, the DIP and the VIP can be on the same NIC.The Client Computer's IP (CIP)The client computer's IP (CIP) address may be a local, private IP address on the same network as the VIP, or it may be a public IP address on the Internet.Types of LVS ClustersNow that we've looked at some of the IP address name conventions used to describe LVS clusters, let's examine the LVS packet-forwarding methods.LVS clusters are usually described by the type of forwarding method the LVS Director uses to relay incoming requests to the nodes inside the cluster. Three methods are currently available:Network address translation (LVS-NAT)Direct routing (LVS-DR)IP tunneling (LVS-TUN)Although more than one forwarding method can be used on a single Director (the forwarding method can be chosen on a per-node basis), I'll simplify this discussion and describe LVS clusters as if the Director is only capable of using one forwarding method at a time.The best forwarding method to use with a Linux Enterprise Cluster is LVS-DR (and the reasons for this will be explained shortly), but an LVS-NAT cluster is theeasiest to build. If you have never built an LVS cluster and want to use one to run your enterprise, you may want to start by building a small LVS-NAT cluster in a lab environment using the instructions in Chapter 12, and then learn how to convert this cluster into an LVS-DR cluster as described in Chapter 13. The LVS-TUN cluster is not generally used for mission-critical applications and is mentioned in this chapter only for the sake of completeness. It will not be described in detail.Network Address Translation (LVS-NAT)In an LVS-NAT configuration, the Director uses the Linux kernel's ability (from the kernel's Netfilter code) to translate network IP addresses and ports as packets pass through the kernel. (This is called Network Address Translation (NAT), and it was introduced in Chapter 2).Note We'll examine the LVS-NAT network communication in more detail in Chapter 12.A request for a cluster service is received by the Director on its VIP, and the Director forwards this requests to a cluster node on its RIP. The cluster node then replies to the request by sending the packet back through the Director so the Director can perform the translation that is necessary to convert the cluster node's RIP address into the VIP address that is owned by the Director. This makes it appear to client computers outside the cluster as if all packets are sent and received from a single IP address (the VIP).Basic Properties of LVS-NATThe LVS-NAT forwarding method has several basic properties:The cluster nodes need to be on the same network (VLAN or subnet) as the Director.The RIP addresses of the cluster nodes normally conform to RFC 1918[2] (that is, they are private, non-routable IP addresses used only for intracluster communication).The Director intercepts all communication (network packets going in either direction) between the client computers and the real servers.The cluster nodes use the Director's DIP as their default gateway for reply packets to the client computers.The Director can remap network port numbers. That is, a request received on the Director's VIP on one port can be sent to a RIP inside the cluster on a different port.Any type of operating system can be used on the nodes inside the cluster.A single Director can become the bottleneck for the cluster.At some point, the Director will become a bottleneck for network traffic as the number of nodes in the cluster increases, because all of the reply packets from the cluster nodes must pass through the Director. However, a 400 MHz processor can saturate a 100 Mbps connection, so the network is more likely to become the bottleneck than the LVS Director under normal circumstances.The LVS-NAT cluster is more difficult to administer than an LVS-DR cluster because the cluster administrator sitting at a computer outside the cluster is blocked from direct access to the cluster nodes, just like all other clients. When attempting to administer the cluster from outside, the administrator must first log on to the Director before being able to telnet or ssh to a specific cluster node. If the cluster is connected to the Internet, and client computers use a web browser to connect to the cluster, having the administrator log on to the Director may be a desirable security feature of the cluster, because an administrative network can be used to allow only internal IP addresses shell access to the cluster nodes. However, in a Linux Enterprise Cluster that is protected behind a firewall, you can more easily administer cluster nodes when you can connect directly to them from outside the cluster. (As we'll see in Part IV of this book, the cluster node manager in an LVS-DR cluster can sit outside the cluster and use the Mon and Ganglia packages to gain diagnostic information about the cluster remotely.)Direct Routing (LVS-DR)In an LVS-DR configuration, the Director forwards all incoming requests to the nodes inside the cluster, but the nodes inside the cluster send their replies directly back to the client computers (the replies do not go back through the Director).[3] As shown in Figure 11-3, the request from the client computer or CIP is sent to the Director's VIP. The Director then forwards the request to a cluster node or real server using the same VIP destination IP address (we'll see how the Director does this inChapter 13). The cluster node then sends a reply packet directly to the client computer, and this reply packet uses the VIP as its source IP address. The client computer is thus fooled into thinking it is talking to a single computer, when in reality it is sending request packets to one computer and receiving reply packets from another.LVS-DR network communicationBasic Properties of LVS-DRThese are the basic properties of a cluster with a Director that uses the LVS- DR forwarding method:The cluster nodes must be on the same network segment as the Director.[4]The RIP addresses of the cluster nodes do not need to be private IP addresses (which means they do not need to conform to RFC 1918).The Director intercepts inbound (but not outbound) communication between the client and the real servers.The cluster nodes (normally) do not use the Director as their default gateway for reply packets to the client computers.The Director cannot remap network port numbers.Most operating systems can be used on the real servers inside the cluster.[5]An LVS-DR Director can handle more real servers than an LVS-NAT Director.Although the LVS-DR Director can't remap network port numbers the way an LVS-NAT Director can, and only certain operating systems can be used on the real servers when LVS-DR is used as the forwarding method,[6] LVS-DR is the best forwarding method to use in a Linux Enterprise Cluster because it allows you to build cluster nodes that can be directly accessed from outside the cluster. Although this may represent a security concern in some environments (a concern that can be addressed with a proper VLAN configuration), it provides additional benefits that can improve the reliability of the cluster and that may not be obvious at first:If the Director fails, the cluster nodes become distributed servers, each with their own IP address. (Client computers on the internal network, in other words, can connect directly to the LVS-DR cluster node using their RIP addresses.) You wouldthen tell users which cluster-node RIP address to use, or you could employ a simple round-robin DNS configuration to hand out the RIP addresses for each cluster node until the Director is operational again.[7] You are protected, in other words, from a catastrophic failure of the Director and even of the LVS technology itself.[8] To test the health and measure the performance of each cluster node, monitoring tools can be used on a cluster node manager that sits outside the cluster (we'll discuss how to do this using the Mon and Ganglia packages in Part IV of this book).To quickly diagnose the health of a node, irrespective of the health of the LVS technology or the Director, you can telnet, ping, and ssh directly to any cluster node when a problem occurs.When troubleshooting what appear to be software application problems, you can tell end-users[9] how to connect to two different cluster nodes directly by IP (RIP) address. You can then have the end-user perform the same task on each node, and you'll know very quickly whether the problem is with the application program or one of the cluster nodes.Note In an LVS-DR cluster, packet filtering or firewall rules can be installed on each cluster node for added security. See the LVS-HOWTO at for a discussion of security issues and LVS. In this book we assume that the Linux Enterprise Cluster is protected by a firewall and that only client computers on the trusted network can access the Director and the real servers.IP Tunneling (LVS-TUN)IP tunneling can be used to forward packets from one subnet or virtual LAN (VLAN) to another subnet or VLAN even when the packets must pass through another network or the Internet. Building on the IP tunneling capability that is part of the Linux kernel, the LVS-TUN forwarding method allows you to place cluster nodes on a cluster network that is not on the same network segment as the Director.Note We will not use the LVS-TUN forwarding method in any recipes in this book, and it is only included here for the sake of completeness.The LVS-TUN configuration enhances the capability of the LVS-DR method ofpacket forwarding by encapsulating inbound requests for cluster services from client computers so that they can be forwarded to cluster nodes that are not on the same physical network segment as the Director. For example, a packet is placed inside another packet so that it can be sent across the Internet (the inner packet becomes the data payload of the outer packet). Any server that knows how to separate these packets, no matter where it is on your intranet or the Internet, can be a node in the cluster, as shown in Figure 11-4.[10]LVS-TUN network communicationThe arrow connecting the Director and the cluster node in Figure 11-4 shows an encapsulated packet (one stored within another packet) as it passes from the Director to the cluster node. This packet can pass through any network, including the Internet, as it travels from the Director to the cluster node.Basic Properties of LVS-TUNAn LVS-TUN cluster has the following properties:The cluster nodes do not need to be on the same physical network segment as the Director.The RIP addresses must not be private IP addresses.The Director can normally only intercept inbound communication between the client and the cluster nodes.The return packets from the real server to the client must not go through the Director. (The default gateway can't be the DIP; it must be a router or another machine separate from the Director.)The Director cannot remap network port numbers.Only operating systems that support the IP tunneling protocol[11] can be servers inside the cluster. (See the comments in the configure-lvs script included with the LVS distribution to find out which operating systems are known to support this protocol.)We won't use the LVS-TUN forwarding method in this book because we want to build a cluster that is reliable enough to run mission-critical applications, and separating the Director from the cluster nodes only increases the potential for acatastrophic failure of the cluster. Although using geographically dispersed cluster nodes might seem like a shortcut to building a disaster recovery data center, such a configuration doesn't improve the reliability of the cluster, because anything that breaks the connection between the Director and the cluster nodes will drop all client connections to the remote cluster nodes. A Linux Enterprise Cluster must be able to share data with all applications running on all cluster nodes (this is the subject of Chapter 16). Geographically dispersed cluster nodes only decrease the speed and reliability of data sharing.[2]RFC 1918 reserves the following IP address blocks for private intranets:10.0.0.0 through 10.255.255.255172.16.0.0 through 172.31.255.255192.168.0.0 through 192.168.255.255[3]Without the special LVS "martian" modification kernel patch applied to the Director, the normal LVS-DR Director will simply drop reply packets if they try to go back out through the Director.[4]The LVS-DR forwarding method requires this for normal operation. See Chapter 13 for more info on LVS-DR clusters[5]The operating system must be capable of configuring the network interface to avoid replying to ARP broadcasts. For more information, see "ARP Broadcasts and the LVS-DR Cluster" in Chapter 13[6]The real servers inside an LVS-DR cluster must be able to accept packets destined for the VIP without replying to ARP broadcasts for the VIP (see Chapter 13)[7]See the "Load Sharing with Heartbeat—Round-Robin DNS" section in Chapter 8 for a discussion of round-robin DNS[8]This is unlikely to be a problem in a properly built and properly tested cluster configuration. We'll discuss how to build a highly available Director in Chapter 15.[9]Assuming the client computer's IP address, the VIP and the RIP are all private (RFC 1918) IP addresses[10]If your cluster needs to communicate over the Internet, you will likely need to encrypt packets before sending them. This can be accomplished with the IPSecprotocol (see the FreeS/WAN project at for details). Buildinga cluster that uses IPSec is outside the scope of this book.[11]Search the Internet for the "Linux 2.4 Advanced Routing HOWTO" for more information about the IP tunneling protocol.LVS Scheduling MethodsHaving discussed three ways to forward packets to the nodes inside the cluster, let's look at how to distribute the workload across the cluster nodes. When the Director receives an incoming request from a client computer to access a cluster service on its VIP, it has to decide which cluster node should get the request. The scheduling methods the Director can use to make this decision fall into two basic categories: fixed scheduling and dynamic scheduling.Note When a node needs to be taken out of the cluster for maintenance, you can set its weight to 0 using either a fixed or a dynamic scheduling method. When a cluster node's weight is 0, no new connections will be assigned to it. Maintenance can be performed after all of the users log out normally at the end of the day. We'll discuss cluster maintenance in detail in Chapter 19.Fixed (or Non-Dynamic) Scheduling MethodsIn the case of fixed, or non-dynamic, scheduling methods, the Director selects the cluster node to use for the inbound request without checking to see how many of the previously assigned connections are active. Here is the current list of fixed scheduling methods:Round-robin (RR)When a new request is received, the Director picks the next server on its list of servers, rotating through them in an endless loop.Weighted round-robin (WRR)You assign each cluster node a weight or ranking, based on how much processing load it can handle. This weight is then used, along with the round-robin technique, to select the next cluster node to be used when a new request is received, regardless of the number of connections that are still active. A server with a weight of 2 will receive twice the number of new connections as a server with a weight of 1. Ifyou change the weight of a server to 0, no new connections will be allowed to the server (but currently active connections will not be dropped). We'll look at how LVS uses this weight to balance the incoming workload in the "Weighted Least-Connection (WLC)" section of this chapter.Destination hashingThis method always sends requests for the same IP address to the same server in the cluster. Like the locality-based least-connection (LBLC) scheduling method (which will be discussed shortly), this method is useful when the servers inside the cluster are really cache or proxy servers.Source hashingThis method can be used when the Director needs to be sure the reply packets are sent back to the same router or firewall that the requests came from. This scheduling method is normally only used when the Director has more than one physical network connection, so that the Director knows which firewall or router to send the reply packet back through to reach the proper client computer.中文翻译:Linux企业集群综述本章将要介绍的是一款叫做IP 虚拟服务器（IPVS）的集群负载均衡软件，它是被合并到Linux2.4.23内核起的主干内核版本的补丁集合，当与内核路由和数据包过滤功能（第2章中讨论了）一起使用时启用了IPVS的内核让你可以将任何运行Linux的计算机变成一个集群负载调度器，启用IPVS的集群负载调度器和集群节点一起叫做一个Linux虚拟服务器（LVS）。