Linux操作系統(tǒng)01-簡(jiǎn)介

1、Linux操作系統(tǒng)簡(jiǎn)介 1Acegene IT Co. Ltd.內(nèi)容提要Linux簡(jiǎn)介L(zhǎng)inux的安裝SHELL及常用程序文件編輯器vi目錄和文件管理文件系統(tǒng)管理用戶管理網(wǎng)絡(luò)管理網(wǎng)絡(luò)文件系統(tǒng)模塊安裝和配置系統(tǒng)管理 系統(tǒng)優(yōu)化開發(fā)工具Internet管理 2Acegene IT Co. Ltd.Linux簡(jiǎn)介 Linux操作系統(tǒng)是可以運(yùn)行在許多不同類型的計(jì)算機(jī)上的一種操作系統(tǒng)的“內(nèi)核”。它是提供命令行或者程序與計(jì)算機(jī)硬件之間接口的軟件的核心部分。Linux操作系統(tǒng)內(nèi)核管理以下事情：比如內(nèi)存、采用什么方法以及在什么時(shí)候打開或者關(guān)閉文件、哪一個(gè)進(jìn)程或者程序可以獲得計(jì)算機(jī)的中央處理單元(CPU)等等。L

2、inux操作系統(tǒng)可以說(shuō)是UNIX操作系統(tǒng)的一個(gè)克隆體，它最初是在1991年10月5日由它的作者Linus Torvalds于赫爾辛基大學(xué)發(fā)布的。3Acegene IT Co. Ltd.Linux功能所有主要的網(wǎng)絡(luò)協(xié)議硬盤配額支持全部的源代碼國(guó)際化的字體和鍵盤作業(yè)控制數(shù)學(xué)協(xié)處理器仿真內(nèi)存保護(hù)多平臺(tái)多處理器多用戶多任務(wù)共享的庫(kù)文件支持多種文件系統(tǒng)虛擬控制臺(tái)虛擬內(nèi)存其他更多功能4Acegene IT Co. Ltd.GPL和FreeLinux操作系統(tǒng)遵從GNU公共許可證（ GNU Public License，簡(jiǎn)稱GPL）的規(guī)定。Linux對(duì)外的一個(gè)重要的特點(diǎn)就是”Free”，自由和免費(fèi)。5Aceg

3、ene IT Co. Ltd.What is Linux?Linux is an operating system with the following attributes:Multi-userMulti-taskingVirtual memory systemX-WindowsCompatible with the IEEE POSIX.1 standardNon-proprietary source codeSource code is available6Acegene IT Co. Ltd.Is Linux the same as UNIX?The command set is si

4、milarThey work the sameThey look the sameLinux cannot use the UNIX trademarkLinux is essentially UNIX7Acegene IT Co. Ltd.Is Linux a real OS?Yes, absolutelyLinux is used In mission critical applicationsAround the worldThere are many flavors of Linux availableWe call them: Distributions8Acegene IT Co.

5、 Ltd.Linux發(fā)行版本的概念大多數(shù)的Linux操作系統(tǒng)的發(fā)行版本都使用標(biāo)準(zhǔn)的Linux內(nèi)核，但有時(shí)候也會(huì)稍微加以修改，這個(gè)操作系統(tǒng)現(xiàn)在的規(guī)模已經(jīng)變得相當(dāng)龐大了，因此許多人更愿意購(gòu)買一張它的CD-ROM光盤。每一種發(fā)行版本彼此之間都稍微有一些差異，這些差異主要表現(xiàn)在它們各自的安裝程序包上，還表現(xiàn)在安全性與可用性等方面?zhèn)戎攸c(diǎn)的不同。把系統(tǒng)內(nèi)核、附帶的工具程序及應(yīng)用軟件包等等打包在一起，這樣組成的一個(gè)Linux操作系統(tǒng)的集合體就是我們說(shuō)的某一種發(fā)行版本。9Acegene IT Co. Ltd.誰(shuí)使用Linux操作系統(tǒng)Linux正在逐漸贏得普通用戶的青睞。但是它仍然不是一個(gè)適用于普通大眾的操作系

6、統(tǒng)。對(duì)那些習(xí)慣了當(dāng)今鼠標(biāo)界面操作系統(tǒng)的人們來(lái)說(shuō)， 學(xué)習(xí)仍是很困難的。需要學(xué)習(xí)一大套從未接觸過(guò)的命令，還需要學(xué)習(xí)與長(zhǎng)期形成的概念不相同的那些對(duì)待與處理事情的方法。對(duì)那些具有UNIX操作系統(tǒng)使用經(jīng)驗(yàn)的人們來(lái)說(shuō)，Linux可是容易多了。專業(yè)用戶、系統(tǒng)管理員和計(jì)算機(jī)開發(fā)人員通常都會(huì)比一般的用戶更容易掌握Linux操作系統(tǒng)。但就是對(duì)這些人來(lái)說(shuō)，這方面的學(xué)習(xí)與實(shí)踐也需要有足夠的耐心與專心。10Acegene IT Co. Ltd.Enterprise vs. RetailRetail distributionsFaster release cycles (4-6 months)Geared for hom

7、e/productivity usersShorter support lifetimesExamples: RHL9, SuSE Linux 9Enterprise level distributionsSlower release cycles (12-18 months)Longer support lifetimes (3-5 years)Examples: RHEL3/4, SLES9Adds performance and scalability enhancements11Acegene IT Co. Ltd.Linux Distribution OverviewThe core

8、 parts of a Linux system are:Linux kernelUser space utilities and applicationsThe kernel and user space programs together make up the complete operating systemLinux KernelCore component of the operating systemConfigurable and tunableProvides main OS functionsI/O, disk, network, etc.CPU SchedulingMem

9、ory managementuname -r shows the kernel version number:# uname -r2.4.9-e.25Kernel conceptsLinux is based on a modular non-microkernel architectureAll device drivers share the same memory with the kernelDevice drivers are modular and can be loaded/unloaded dynamicallyLinux is multi-taskingLinux is a

10、virtual-memory OSMost kernel parameters can be modified on the fly14Acegene IT Co. Ltd.All components of the operating system are delivered via RPM packagesKernelSystem utilitiesApplicationsBoth Red Hat and SLES8 distributions use the RPM Package Manager (RPM)Originally named “Red Hat Package Manage

11、r”Software PackagesLinux UpdatesApply the recommended updates by the distribution vendor:Most vendors provide automatic updatesRed Hat Network supplies updates automaticallyup2dateSuSE usesYaST2 (Yet Another Setup Tool 2)you (YaST Online Update)Linux Enterprise FeaturesLinux enterprise features supp

12、ort :PerformanceScalabilityReliabilitySymmetric MultiprocessingFully multiprocessor capable (SMP)RHEL3: 16 processorsSLES8: 32 processorsUniprocessor configuration supported on bothIntel Hyperthreading (HT) enabled on IA-32Physical-to-logical CPU affinity scheduling18Acegene IT Co. Ltd.Improved Memo

13、ry UtilizationUse more than 4GB of RAM on IA-32RHEL 2.1: max 16GB supportedRHEL3: max 64GB supportedSLES8: up to 64GB supportedSome older drivers not capable of accessing more than 4GB of RAMMay perform “bounce buffering” to compensateUsually not a concern for enterprise-class driversKernel memory u

14、sed more efficiently than beforeRun more processes without swapping19Acegene IT Co. Ltd.Virtual MemoryEach process has a private address spaceKeeps private data in memory securePrevents inter-process data corruptionContiguous view of memoryDemand-based pagingPages are “swapped” out when low on RAMPa

15、ges are “swapped” in when accessed againAllows the system to use more memory than any single space can address20Acegene IT Co. Ltd.Virtual Filesystem (VFS)Linux supports multiple file systemsOS is file system independentMultiple file systems can be used simultaneouslyCross-platform compatibilityPerf

16、ormanceVFS provides a single filesystem interfaceFilesystemsImportant ones to know:ext2/3 - Red Hat default (ext3)reiserfs - SLES8 defaultNFS - Network FilesystemProcfs - kernel virtual filesystemISO 9660 (CD-ROM)OCFS - Oracle Cluster Filesystemext2/3 and reiserfs are the most commonUse OCFS instead

17、 of raw devices in RAC22Acegene IT Co. Ltd.Filesystem CacheBuffers all filesystem I/OAll filesystem I/O is copied to/from cache buffersBy default, writes are not immediately flushedHardware I/O is deferredReads benefit from previous accesses as well as automatic read-aheadMay not need to perform a r

18、eal hardware I/OMade up of page cache and buffer cachePage cache tends to be more heavily usedReduced automatically when low on RAM23Acegene IT Co. Ltd.ProcessDisk fileWriteReadRaw DevicesHave traditionally been considered the high performance solutionBypasses the filesystem buffer cacheMoves larger

19、 buffers than file system I/OsRequires more experienced administration24Acegene IT Co. Ltd.Modular DriversLoadable kernel modules (LKM)Can be unloaded/reloaded without rebootingModules provide:Device driversFile system driversSystem callsNetwork driversExecutable interpretersTerminal device (TTY) dr

20、ivers25Acegene IT Co. Ltd.I/O ModesDisk I/O can be performed in several different modesAsynchronous vs. synchronous Direct vs. bufferedProcessBuffer cacheDisk fileWriteFlushStorage InfrastructureDirect-attached storage (DAS)IDE, SCSIe.g., LSI MegaraidNetwork-Attached Storage (NAS)NFSe.g., Network Ap

21、pliance FilerStorage Area Networks (SAN)FibreChannele.g., EMC Clariion27Acegene IT Co. Ltd.Linux ClustersScalable Shared StorageSCSI, SAN (FibreChannel), Firewire (devel.)Must use raw devices or OCFSNetwork Attached Storage (NFS)LVM and software RAID (“md”) not cluster-awareLinux includes cluster management software28Acegene IT Co. Ltd.Linux Kernel EnhancementsPerformanceAsynchronous I/OEliminate kernel locksLarge SGA: 4 GBSupport more Oracle usersStabilityGraceful degradation under loadManageability(Remote) Crash Dump FacilityConfiguration scripts29Acegene IT Co. Ltd.Kernel Asynchrono