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Chapter 1.  Introduction to Linux

Chapter 1.  Introduction to Linux

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officework,butyoucanalsolearnhowtowritedatabase

queries,administerawebserver,filtermailforspamand

viruses,automateyourenvironmentthroughscripting

languages,accesswebservices,andparticipateinthemyriadof

othercutting-edgeactivitiesprovidedbymoderncomputing.

HowdoesLinuxdoallthosethings?Linuxdistributionsharvest

vastamountsofdiversetechnology,especiallynewand

innovativedevelopmentsinhardware.Developershaveaccess

toallthecodethatmakesuptheoperatingsystem.Although

manypeopleconsiderLinuxthelargestcooperativesoftware

developmentprojectinhumanhistory,Linuxdevelopersdon't

needtoevenknoweachother.Ifsomeonewantstowritea

softwareapplication,allhehastodoisdownloadtheLinux

codeorvisititsdocumentationsite.Ifyoustartedcounting

peoplewhohavecontributedtothedevelopmentofLinuxand

itsassociatedprojects,youwouldseehundredsofthousandsof

individuals.

Linuxandopensourcesoftwaredeveloperscomefrommany

walksoflife.MajorcomputervendorssuchasIBM,HP,Novell,

RedHat,Sun,Dell,andotherspayportionsoftheirstaffsto

workonLinux.Universitiesaroundtheglobesponsorprojects

andfoundationsthatcontributetoLinux.TheU.S.Department

ofDefense,NASA,andtheNationalSecurityAgencyhavepaid

fornumerouspiecesoftheLinuxoperatingsystem.Developing

countriessuchasChina,Brazil,Malaysia,SouthAfrica,andViet

Nam,tomentionafew,haveaddedtotheLinuxbase.

IndustrialgiantssuchasGermany,Australia,Japan,theUnited

Kingdom,andothershavealsomadetheirpresencefelt.Butin

theverymidstofthosegiants,manyindividualssuchasyou

andmehavealsocontributedtoLinux.

Duringthe1990s,Linuxgeneratedmoreexcitementinthe

computerfieldthananyotherdevelopmentsincetheadventof

microprocessortechnology.Linuxrejuvenatedadying

technologysectorfollowingthefallofthedot-comboominthe

springof2001.Today,Linuxhassurpassedtheexpectationsof



informedobserversworldwide,includingtheauthorsofthis

book.

Earlyon,Linuxinspiredandcapturedtheloyaltyofitsusers.

TechnologistsinterestedintheserversideoftheInternet

neededtobecomefamiliarwiththeoperatingsystemsthatran

websites,domainnameservices,andemailandservice

providers.Traditionalsoftwaremanufacturerspricedtheir

systemsoutoftherangeofthosewantingtogainwebmastertypeskills.ManypeopleviewedLinuxasagodsendbecause

youcoulddownloaditforfreeandgaintheskillsnecessaryto

becomeawebmasterorsystemadministratorwhileworkingon

relativelylow-costhardware.

Originally,peoplesawLinuxassimplyanoperatingsystem

kernel,offeringthebasicservicesofprocessscheduling,virtual

memory,filemanagement,andhandlingofhardware

peripheralssuchasharddrives,DVDs,printers,terminals,and

soforth.OtherInternetoperatingsystemsbelongedtotheUnix

family,whichbecameavailableforcommercialsaleonlyafter

thebreakupofAT&TandtheBellOperatingSystems.

ToskirtthelegalissuessurroundingAT&T'sUnix,theFree

SoftwareFoundation(FSF)createdaplethoraofapplications

thatperformedmanyofthefunctionsofbasicUnixwhileusing

totallyoriginalFSFcodeinsteadofcodeproducedbyBellLabs.

ThiscollectionofFSFsoftwarewascalledGNU.Tobecomea

completeoperatingsystem,however,FSFneededakernel.

Althoughtheirowneffortsinthatareastalled,anoperating

systemfittingthebillaroseunexpectedlyfromeffortsbya

studentattheUniversityofHelsinkiinFinland:LinusTorvalds.

Peoplenowusetheterm"Linux"torefertothecomplete

systemthekernelalongwiththemanyapplicationsthatitruns:

acompletedevelopmentandworkenvironmentincluding

compilers,editors,graphicalinterfaces,textprocessors,games,

andmore.FSFproponentsaskthatthisbroadercollectionof

softwarebeknownas"GNU/Linux."







1.1.AboutThisBook

ThisbookprovidesanoverviewandguidetoLinuxasadesktop

andaback-officesystem.Wepresentinformationontopicsto

satisfynovicesandwizardsalike.Thisbookshouldprovide

sufficientmaterialforalmostanyonetochoosethetypeof

installationtheywantandgetthemostoutofit.Insteadof

coveringmanyofthevolatiletechnicaldetailsthosethingsthat

tendtochangewithLinux'srapiddevelopmentwegiveyouthe

informationthathelpsyouoverthebumpsasyoutakeyour

firststepswithpopulardistributions,aswellasbackgroundyou

willneedifyouplantogoontomoreadvancedLinuxtopics

suchaswebservices,federatedidentitymanagement,highperformancecomputing,andsoon.

Wegearedthisbookforthosepeoplewhowanttounderstand

thepowerthatLinuxcanprovide.Ratherthanprovideminimal

information,wehelpyouseehowthedifferentpartsofthe

Linuxsystemwork,soyoucancustomize,configure,and

troubleshootthesystemonyourown.Linuxisnotdifficultto

installanduse.Manypeopleconsideriteasierandfastertoset

upthanMicrosoftWindows.However,aswithanycommercial

operatingsystem,someblackmagicexists,andyouwillfind

thisbookusefulifyouplantogobeyonddesktopLinuxanduse

webservicesornetworkmanagementservices.

Inthisbook,wecoverthefollowingtopics:

ThedesignandphilosophyoftheLinuxoperatingsystem,

andwhatitcandoforyou.

InformationonwhatyouneedtorunLinux,including

suggestionsonhardwareplatformsandhowtoconfigure

theoperatingsystemdependingonitsspecifiedrole(e.g.,

desktop,webserver,databaseand/orapplicationserver).



HowtoobtainandinstallLinux.WecovertheRedHat,

SUSE,andDebiandistributionsinmoredetailthanothers,

buttheinformationisusefulinunderstandingjustabout

anydistribution.

Anintroduction,fornewusers,totheoriginalLinux/Unix

systemphilosophy,includingthemostimportantcommands

andconceptsstillinuse.

Personalproductivitythroughslickandpowerfuloffice

suites,imagemanipulation,andfinancialaccounting.

ThecareandfeedingoftheLinuxsystem,includingsystem

administrationandmaintenance,upgradingthesystem,and

howtofixthingswhentheydon'twork.

ExpandingthebasicLinuxsystemanddesktop

environmentswithpowertoolsforthetechnicallyinclined.

TheLinuxprogrammingenvironment.Thetoolsofthetrade

forprogramminganddevelopingsoftwareontheLinux

system.

UsingLinuxfortelecommunicationsandnetworking,

includingthebasicsofTCP/IPconfiguration,PPPfor

Internetconnectivityoveramodem,ISDNconfiguration,

ADSL,cable,email,news,andwebaccessweevenshow

howtoconfigureaLinuxsystemasawebanddatabase

server.

Linuxforfun:audio,video,andgames.

Manythingsexistthatwe'dlovetoshowyouhowtodowith

Linux.Unfortunately,tocoverthemall,thisbookwouldbethe

sizeoftheunabridgedOxfordEnglishDictionaryandwouldbe



impossibleforanyone(letalonetheauthors)tomaintain.

Insteadwe'veincludedthemostsalientandinterestingaspects

ofthesystemandshowyouhowtofindoutmore.

Althoughmuchofthediscussioninthisbookisnotoverly

technical,you'llfinditeasiertonavigateifyouhavesome

experiencewiththecommandlineandtheeditingofsimpletext

files.Forthosewhodon'thavesuchexperience,wehave

includedashorttutorialinChapter4.Part2ofthebookisan

explorationofsystemadministrationthatcanhelpeven

seasonedtechniciansrunLinuxinaservermode.

IfyouarenewtoLinuxandwantmoresystem-oriented

information,you'llwanttopickupanadditionalguideto

command-linebasics.Wedon'tdwellforlongonthe

fundamentals,preferringinsteadtoskiptothefunpartsofthe

system.Atanyrate,althoughthisbookshouldbeenoughto

getyoufunctionalandevenseasonedintheuseofLinux,you

mayhaverequirementsthatwilltakeyouintospecializedareas.

SeeAppendixAforalistofsourcesofinformation.







1.2.Who'sUsingLinux?

Applicationdevelopers,systemadministrators,network

providers,kernelhackers,students,andmultimediaauthorsare

justafewofthecategoriesofpeoplewhofindthatLinuxhasa

particularcharm.

ProgrammersareincreasinglyusingLinuxbecauseofits

extensibilityandlowcosttheycanpickupacomplete

programmingenvironmentforfreeandrunitoninexpensivePC

hardwareandbecauseLinuxoffersagreatdevelopment

platformforportableprograms.InadditiontotheoriginalFSF

tools,Linuxcanutilizeanumberofdevelopmentenvironments

thathavesurfacedoverthelastthreeyears,suchasEclipse

(http://eclipse.org).Eclipseisquiteaphenomenon:atributeto

boththecreativityoftheopensourcecommunityandthe

fertilityofacollaborationbetweenanopensourcecommunity

andamajorvendor(Eclipsewasoriginallydevelopedand

releasedbyIBM).Itisanopensourcecommunityfocusedon

providinganextensibledevelopmentplatformandapplication

frameworksforbuildingsoftware.

Eclipse'stoolsandframeworksspanthesoftwaredevelopment

lifecycle,includingsupportformodeling;language

developmentenvironmentsforJava?,C/C++,andother

languages;testingandperformance;businessintelligence;rich

clientapplications;andembeddeddevelopment.Alarge,

vibrantecosystemofmajortechnologyvendors,innovative

startups,universities,andresearchinstitutionsandindividuals

extend,complement,andsupporttheEclipseplatform.

NetworkingisoneofLinux'sstrengths.Linuxhasbeenadopted

bypeoplewhorunlargenetworksbecauseofitssimplicityof

management,performance,andlowcost.ManyInternetsites

makeuseofLinuxtodrivelargewebservers,e-commerce

applications,searchengines,andmore.Linuxiseasytomerge



intoacorporateoracademicnetworkbecauseitsupports

commonnetworkingstandards.Theseincludebotholdstandbys,suchastheNetworkFileSystem(NFS)andNetwork

InformationService(NIS),andmoreprominentsystemsused

inmodernbusinesses,suchasMicrosoftfilesharing(CIFSand

relatedprotocols)andLightweightDirectoryAccessProtocol

(LDAP).Linuxmakesiteasytosharefiles,supportremote

logins,andrunapplicationsonothersystems.Asoftwaresuite

calledSambaallowsaLinuxmachinetoactasaWindows

serverinActiveDirectoryenvironments.Thecombinationof

LinuxandSambaforthispurposeisfaster(andlessexpensive)

thanrunningWindowsServer2003.Infact,giventheeasewith

whichLinuxsupportscommonnetworkingactivitiesDHCP,the

DomainNameSystem,Kerberossecurity,routingit'shardto

imagineacorporatenetworkingtaskforwhichit'sunsuited.

OneofthemostpopularusesofLinuxisindrivinglarge

enterpriseapplications,includingwebservers,databases,

business-to-businesssystems,ande-commercesites.

BusinesseshavelearnedthatLinuxprovidesaninexpensive,

efficient,androbustsystemcapableofdrivingthemost

mission-criticalapplications.

Asjustoneexampleamongthemanypublicizedeachmonth,

CendantTravelDistributionServicesputitsFaresapplicationon

aLinuxEnterpriseServerwithIBMxSeriesandBladeCenter

serversasthehardwareplatforms.Themovereduced

expendituresby90%whileachieving99.999%availabilityand

handling300to400transactionspersecond.

Linux'seaseofcustomizationevendowntothegutsofthe

kernelmakesthesystemveryattractiveforcompaniesthat

needtoexercisecontrolovertheinnerworkingsofthesystem.

Linuxsupportsarangeoftechnologiesthatensuretimelydisk

accessandresistancetofailure,fromRAID(asetof

mechanismsthatallowanarrayofdiskstobetreatedasa

singlelogicalstoragedevice)tothemostsophisticatedstorage

areanetworks.Thesegreatlyincreasereliabilityandreducethe



costsofmeetingnewregulatorydemandsthatrequirethe

warehousingofdataforaslongas30years.

ThecombinationofLinux,theApachewebserver,theMySQL

databaseengine,andthePHPscriptinglanguageissocommon

thatithasitsownacronymLAMP.WecoverLAMPinmoredetail

inChapter25.

KernelhackerswerethefirsttocometoLinuxinfact,the

developerswhohelpedLinusTorvaldscreateLinuxarestilla

formidablecommunity.TheLinuxkernelmailinglistsseea

greatdealofactivity,andit'stheplacetobeifyouwanttostay

onthebleedingedgeofoperatingsystemdesign.Ifyou'reinto

tuningpagereplacementalgorithms,twiddlingnetwork

protocols,oroptimizingbuffercaches,Linuxisagreatchoice.

Linuxisalsogoodforlearningabouttheinternalsofoperating

systemdesign,andanincreasingnumberofuniversitiesmake

useofLinuxsystemsinadvancedoperatingsystemcourses.

Finally,Linuxisbecominganexcitingforumformultimedia

becauseit'scompatiblewithanenormousvarietyofhardware,

includingthemajorityofmodernsoundandvideocards.

Severalprogrammingenvironments,includingtheMESA3D

toolkit(afreeOpenGLimplementation),havebeenportedto

Linux;OpenGLisintroducedin"IntroductiontoOpenGL

Programming"inChapter21.TheGIMP(afreeAdobe

Photoshopwork-alike)wasoriginallydevelopedunderLinux,

andisbecomingthegraphicsmanipulationanddesigntoolof

choiceformanyartists.Manymovieproductioncompanies

regularlyuseLinuxastheworkhorseforadvancedspecialeffectsrenderingthepopularmoviesTitanicandTheMatrixused

"renderfarms"ofLinuxmachinestodomuchoftheheavy

lifting.

LinuxsystemshavetraveledthehighseasoftheNorthPacific,

managingtelecommunicationsanddataanalysisfor

oceanographicresearchvessels.Linuxsystemsareusedat

researchstationsinAntarctica,andlarge"clusters"ofLinux



machinesareusedatmanyresearchfacilitiesforcomplex

scientificsimulationsrangingfromstarformationto

earthquakes,andinDepartmentofEnergylaboratorieshelping

tobringnewsourcesofenergytoeveryone.Onamorebasic

level,hospitalsuseLinuxtomaintainpatientrecordsand

retrievearchives.TheU.S.judiciaryusesLinuxtomanageits

entireinfrastructure,fromcasemanagementtoaccounting.

FinancialinstitutionsuseLinuxforreal-timetradingofstocks,

bonds,andotherfinancialinstruments.Linuxhastakenover

therolethatUnixusedtoplayasthemostreliableoperating

system.







1.3.SystemFeatures

Linuxhassurpassedthefeaturesfoundinimplementationsof

UnixandWindows.WiththechangesofferedbyIBM'sPower

Architecture,forexample,Linuxprovidesfunctionalityfor

commodityhardwarenormallyonlyfoundonthemost

expensivemainframes.Additionally,thelatestkernelsinclude

thestructureofSecurityEnhancedLinux(SELinux)providedby

theNationalSecurityAgency(http://www.nsa.gov/selinux).

SELinuxprovidesthemosttrustedcomputingenvironment

availabletoday.

NowaddLinux'sabilitytoprovidevirtualizationatthekernel

level.ThroughXen(http://sourceforge.net/projects/xen),Linux

cansecurelyexecutemultiplevirtualmachines,eachrunningits

ownoperatingsystem,onasinglephysicalsystem.Thisallows

enterprisestostopserversprawlandincreaseCPUutilization.



1.3.1.ABagofFeatures

ThissectionprovidesanickeltourofLinuxfeatures.

Linuxisacompletemultitasking,multiuseroperatingsystem

(asareallotherversionsofUnix).Thismeansthatmanyusers

canbeloggedontothesamemachineatonce,runningmultiple

programssimultaneously.Linuxalsosupportsmultiprocessor

systems(suchasdual-Pentiummotherboards),withsupportfor

upto32processorsinasystem,[*]whichisgreatforhighperformanceserversandscientificapplications.

[*]Ona32-bitarchitecture;ona64-bitarchitecture,upto64CPUsaresupported,andpatchesareavailable

thatsupportupto256CPUs.



TheLinuxsystemismostlycompatiblewithanumberofUnix



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