linux-lecture6 LINUX SYSTEM ADMINISTRATION

LinuxSystemAdministrationLINUXSYSTEMADMINISTRATIONSYSADMINTASKSLinuxSystemAdministrationSettingtheRunLevelSystemServicesUserManagementNetworkSettingsSchedulingJobsQuotaManagementBackupandRestoreAddingandRemovingsoftware/packagesSettingaPrinterMonitoringthesystem(general,logs)Monitoringanyspecificservicesrunning.Eg.DNS,DHCP,Web,NIS,NPT,Proxyetc.InitRunlevelsLinuxSystemAdministrationThefollowingrunlevelsaredefinedinLinux:0-halt(DoNOTsetinitdefaulttothis)1-Singleusermode2-Multiuser,withoutNetwork(Thesameas3,ifyoudonothavenetworking)3–TextMode4-unused5–GraphicalMode6-reboot(DoNOTsetinitdefaulttothis)InitRunlevelsDesktopConfigurationThedefaultrunlevelforasystemtoboottoisconfiguredin/etc/inittab.id:5:initdefault:InGUI:ApplicationsSystemSettingsServerSettingsServicesGenerally,Linuxoperatesinrunlevel3or5.LinuxServicesLinuxSystemAdministrationThereare113deamons,Outofthem,thefollowingaremostwidelyused:apmd:PowerManagementautofs:Automountservicescrond:PeriodicCommandSchedulercups:CommonUnixPrintingSystemdhcpd:TheDHCPserverdovecot:IMAP(InternetMessageAccessProtocol)andPOP3(PostOfficeProtocol)servergpm:Mousehttpd:ApacheWebserverLinuxServicesLinuxSystemAdministrationiptables:KernelbasedPacketFilteringfirewallkudzu:FindsnewHardwaremysqld:MySQLservernamed:BINDservernetwork:Networkingnfs:NetworkFileSharenfslock:NFSfilelockingntpd:NTP(NetworkTimeProtocol)serverportmap:RPC(RemoteProcedureCall)supportpostgresql:ThePostgresqlDatabaseEngineLinuxServicesLinuxSystemAdministrationsendmail:SendmailMailServersmb:SambaNetworkServicessnmpd:SimpleNetworkManagementProtocolsquid:SquidProxyServersshd:OpenSSHandSFTPserversyslog:SystemLoggingxinetd:Providessupportfortelnet,ftp,talk,tftpetc.ypbind:NISServerLinuxServicesLinuxSystemAdministrationStart/Stopboottimeservicesin/etc/rc.d/rc3.dor/etc/rc.d/rc5.dAllservicesstartupscriptswhichstartwithSwillstartatboottimeandallstartupscriptswhichstartwithKwillnotstartatboottime.ThenumberafterSorKisthepriority.K95kudzuK96pcmciaS56xinetdS60vsftpdUseserviceservicenamestart/stop/restarttostart,stoporrestartaservicefromcommandlineCreatinganewUserAccountLinuxSystemAdministrationAddanentryin/etc/passwdand/etc/shadowfile(usenextuidandsuitablegid).YouwillhavetocreatetheuserdirectoryandassignapasswordtotheuserUseuseraddoraddusercommandtocreateanewuser(useradd–ggroup-dhomedirectory-ccomment-sshelllogin-name)andgroupaddtocreateanewgroup(groupaddgroup-name).Youwillhavetoassignapassword(passwdlogin-name)InGUI:ApplicationsSystemSettingsUsersandGroups/etc/passwdFileLinuxSystemAdministration/etc/passwdHoldsuseraccountinfoIncludedfieldsare:LoginnameUserId(uid)GroupId(gid)GeneralCommentabouttheuserHomeDirectoryShell/etc/shadowFileLinuxSystemAdministration/etc/shadowContainstheencryptedpasswordinformationforusers'accountsandoptionallythepasswordaginginformation.Includedfieldsare:LoginnameEncryptedpasswordDayssinceJan1,1970thatpasswordwaslastchangedDaysbeforepasswordmaynotbechangedDaysafterwhichpasswordmustbechangedDaysbeforepasswordistoexpirethatuseriswarnedDaysafterpasswordexpiresthataccountisdisabledDayssinceJan1,1970thataccountisdisabledSuspendingaUserAccountLinuxSystemAdministrationPuta*asstartofPasswordfieldin/etc/shadowChangeloginshellto/sbin/nologinUseGUItosuspendtheuserRemovingaUserAccountLinuxSystemAdministrationRemoveloginidfrom/etc/passwd&/etc/shadowfileanddeletehomedirectoryuserdel–rusernameUseGUItoDeletetheuser