Linux操作系統(tǒng)

簡(jiǎn)介周炯上海艾基信息技術(shù)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(kāi)發(fā)工具Internet管理Linux——簡(jiǎn)介L(zhǎng)inux操作系統(tǒng)是可以運(yùn)轉(zhuǎn)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中心部分。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)候翻開(kāi)或者封鎖文件、哪一個(gè)進(jìn)程或者程序可以獲得計(jì)算機(jī)的中央處置單元(CPU)等等。Linux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LinusTorvalds于赫爾辛基大學(xué)發(fā)布的。Linux功能一切主要的網(wǎng)絡(luò)協(xié)議硬盤(pán)配額支持全部的源代碼國(guó)際化的字體和鍵盤(pán)作業(yè)控制數(shù)學(xué)協(xié)處置器仿真內(nèi)存維護(hù)多平臺(tái)多處置器多用戶多義務(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GPL和FreeLinux操作系統(tǒng)服從GNU公共答應(yīng)證〔GNUPublicLicense，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〞，自在和免費(fèi)。WhatisLinux?Linuxisanoperatingsystemwiththefollowingattributes:Multi-userMulti-taskingVirtualmemorysystemX-WindowsCompatiblewiththeIEEEPOSIX.1standardNon-proprietarysourcecodeSourcecodeisavailableIsLinuxthesameasUNIX?ThecommandsetissimilarTheyworkthesameTheylookthesameLinuxcannotusetheUNIXtrademarkLinuxisessentiallyUNIXIsLinuxarealOS?Yes,absolutelyLinuxisusedInmissioncriticalapplicationsAroundtheworldTherearemanyflavorsofLinuxavailableWecallthem:DistributionsLinux發(fā)行版本的概念大多數(shù)的Linux操作系統(tǒng)的發(fā)行版本都運(yùn)用規(guī)范的Linux內(nèi)核，但有時(shí)候也會(huì)略微加以修正，這個(gè)操作系統(tǒng)如今的規(guī)模曾經(jīng)變得相當(dāng)龐大了，因此許多人更情愿購(gòu)買一張它的CD-ROM光盤(pán)。每一種發(fā)行版本彼此之間都略微有一些差別，這些差別主要表如今它們各自的安裝程序包上，還表如今平安性與可用性等方面偏重點(diǎn)的不同。把系統(tǒng)內(nèi)核、附帶的工具程序及運(yùn)用軟件包等等打包在一同，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。誰(shuí)運(yùn)用Linux操作系統(tǒng)Linux正在逐漸博得普通用戶的青睞。但是它依然不是一個(gè)適用于普通群眾的操作系統(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。需求學(xué)習(xí)一大套從未接觸過(guò)的命令，還需求學(xué)習(xí)與長(zhǎng)期構(gòu)成的概念不一樣的那些對(duì)待與處置事情的方法。對(duì)那些具有UNIX操作系統(tǒng)運(yùn)用閱歷的人們來(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(kāi)發(fā)人員通常都會(huì)比普通的用戶更容易掌握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)際也需求有足夠的耐心與專心。Enterprisevs.RetailRetaildistributionsFasterreleasecycles(4-6months)Gearedforhome/productivityusersShortersupportlifetimesExamples:RHL9,SuSELinux9EnterpriseleveldistributionsSlowerreleasecycles(12-18months)Longersupportlifetimes(3-5years)Examples:RHEL3/4,SLES9AddsperformanceandscalabilityenhancementsLinuxDistributionOverviewThecorepartsofaLinuxsystemare:LinuxkernelUserspaceutilitiesandapplicationsThekernelanduserspaceprogramstogethermakeupthecompleteoperatingsystemLinuxKernelCorecomponentoftheoperatingsystemConfigurableandtunableProvidesmainOSfunctionsI/O,disk,network,etc.CPUSchedulingMemorymanagementuname-rshowsthekernelversionnumber:#uname-r2.4.9-e.25KernelconceptsLinuxisbasedonamodularnon-microkernelarchitectureAlldevicedriverssharethesamememorywiththekernelDevicedriversaremodularandcanbeloaded/unloadeddynamicallyLinuxismulti-taskingLinuxisavirtual-memoryOSMostkernelparameterscanbemodifiedontheflyAllcomponentsoftheoperatingsystemaredeliveredviaRPMpackagesKernelSystemutilitiesApplicationsBothRedHatandSLES8distributionsusetheRPMPackageManager(RPM)Originallynamed“RedHatPackageManager〞SoftwarePackagesLinuxUpdatesApplytherecommendedupdatesbythedistributionvendor:MostvendorsprovideautomaticupdatesRedHatNetworksuppliesupdatesautomaticallyup2dateSuSEusesYaST2(YetAnotherSetupTool2)you(YaSTOnlineUpdate)LinuxEnterpriseFeaturesLinuxenterprisefeaturessupport:PerformanceScalabilityReliabilitySymmetricMultiprocessingFullymultiprocessorcapable(SMP)RHEL3:16processorsSLES8:32processorsUniprocessorconfigurationsupportedonbothIntelHyperthreading(HT)enabledonIA-32Physical-to-logicalCPUaffinityschedulingImprovedMemoryUtilizationUsemorethan4GBofRAMonIA-32RHEL2.1:max16GBsupportedRHEL3:max64GBsupportedSLES8:upto64GBsupportedSomeolderdriversnotcapableofaccessingmorethan4GBofRAMMayperform“bouncebuffering〞tocompensateUsuallynotaconcernforenterprise-classdriversKernelmemoryusedmoreefficientlythanbeforeRunmoreprocesseswithoutswappingVirtualMemoryEachprocesshasaprivateaddressspaceKeepsprivatedatainmemorysecurePreventsinter-processdatacorruptionContiguousviewofmemoryDemand-basedpagingPagesare“swapped〞outwhenlowonRAMPagesare“swapped〞inwhenaccessedagainAllowsthesystemtousemorememorythananysinglespacecanaddressVirtualFilesystem(VFS)LinuxsupportsmultiplefilesystemsOSisfilesystemindependentMultiplefilesystemscanbeusedsimultaneouslyCross-platformcompatibilityPerformanceVFSprovidesasinglefilesysteminterfaceFilesystemsImportantonestoknow:ext2/3-RedHatdefault(ext3)reiserfs-SLES8defaultNFS-NetworkFilesystemProcfs-kernelvirtualfilesystemISO9660(CD-ROM)OCFS-OracleClusterFilesystemext2/3andreiserfsarethemostcommonUseOCFSinsteadofrawdevicesinRACFilesystemCacheBuffersallfilesystemI/OAllfilesystemI/Oiscopiedto/fromcachebuffersBydefault,writesarenotimmediatelyflushedHardwareI/OisdeferredReadsbenefitfrompreviousaccessesaswellasautomaticread-aheadMaynotneedtoperformarealhardwareI/OMadeupofpagecacheandbuffercachePagecachetendstobemoreheavilyusedReducedautomaticallywhenlowonRAMProcessDiskfileWriteReadRawDevicesHavetraditionallybeenconsideredthehighperformancesolutionBypassesthefilesystembuffercacheMoveslargerbuffersthanfilesystemI/OsRequiresmoreexperiencedadministrationModularDriversLoadablekernelmodules(LKM)Canbeunloaded/reloadedwithoutrebootingModulesprovide:DevicedriversFilesystemdriversSystemcallsNetworkdriversExecutableinterpretersTerminaldevice(TTY)driversI/OModesDiskI/OcanbeperformedinseveraldifferentmodesAsynchronousvs.synchronousDirectvs.bufferedProcessBuffercacheDiskfileWriteFlushStorageInfrastructureDirect-attachedstorage(DAS)IDE,SCSIe.g.,LSIMegaraidNetwork-AttachedStorage(NAS)NFSe.g.,NetworkApplianceFilerStorageAreaNetworks(SAN)FibreChannele.g.,EMCClariionLinuxClustersScalableSharedStorageSCSI,SAN(FibreChannel),Firewire(devel.)MustuserawdevicesorOCFSNetworkAttachedStorage(NFS)LVMandsoftwareRAID(“md〞)notcluster-awareLinuxincludesclustermanagementsoftwareLinuxKernelEnhancementsPerformanceAsynchronousI/OEliminatekernellocksLargeSGA:>4GBSupportmoreOracleusersStabilityGracefuldegradationunderloadManageability(Remote)CrashDumpFacilityConfigurationscriptsK