Linux命令学习总结：详解shutdown命令
本文讲诉了Linux命令学习总结：shutdown命令，具体如下：
命令简介：
该命令可以安全关闭或者重新启动系统。你没有看错，shutdown命令不仅可以关闭系统、也可以重启Linux系统。
命令语法：
/sbin/shutdown[-tsec][-arkhncfFHP]time[warning-message]
命令参数：
使用示例：
1:查看reboot命令的帮助信息
[root@db-server~]#shutdown--help shutdown:invalidoption--- Usage:shutdown[-akrhHPfnc][-tsecs]time[warningmessage] -a:use/etc/shutdown.allow -k:don'treallyshutdown,onlywarn. -r:rebootaftershutdown. -h:haltaftershutdown. -P:haltactionistoturnoffpower. -H:haltactionistojusthalt. -f:doa'fast'reboot(skipfsck). -F:Forcefsckonreboot. -n:donotgothrough"init"butgodownrealfast. -c:cancelarunningshutdown. -tsecs:delaybetweenwarningandkillsignal. **the"time"argumentismandatory!(try"now")** [root@db-server~]#
[root@db-server~]#manshutdown SHUTDOWN(8)LinuxSystemAdministrator鈥檚ManualSHUTDOWN(8) NAME shutdown-bringthesystemdown SYNOPSIS /sbin/shutdown[-tsec][-arkhncfFHP]time[warning-message] DESCRIPTION shutdownbringsthesystemdowninasecureway.Alllogged-inusersarenotifiedthatthesystemisgoing down,andlogin(1)isblocked.Itispossibletoshutthesystemdownimmediatelyorafteraspecifieddelay. AllprocessesarefirstnotifiedthatthesystemisgoingdownbythesignalSIGTERM.Thisgivesprogramslike vi(1)thetimetosavethefilebeingedited,mailandnewsprocessingprogramsachancetoexitcleanly,etc. shutdowndoesitsjobbysignallingtheinitprocess,askingittochangetherunlevel.Runlevel0isusedto haltthesystem,runlevel6isusedtorebootthesystem,andrunlevel1isusedtoputtosystemintoastate whereadministrativetaskscanbeperformed;thisisthedefaultifneitherthe-hor-rflagisgiventoshut- down.Toseewhichactionsaretakenonhaltorrebootseetheappropriateentriesfortheserunlevelsinthe file/etc/inittab. OPTIONS -aUse/etc/shutdown.allow. -tsecTellinit(8)towaitsecsecondsbetweensendingprocessesthewarningandthekillsignal,before changingtoanotherrunlevel. -kDon鈥檛reallyshutdown;onlysendthewarningmessagestoeverybody. -rRebootaftershutdown. -hHaltorpoweroffaftershutdown. -HHaltactionistohaltordropintobootmonitoronsystemsthatsupportit. -PHaltactionistoturnoffthepower. -n[DEPRECATED]Don鈥檛callinit(8)todotheshutdownbutdoitourself.Theuseofthisoptionisdis- couraged,anditsresultsarenotalwayswhatyou鈥檇expect. -fSkipfsckonreboot. -FForcefsckonreboot. -cCancelanalreadyrunningshutdown.Withthisoptionitisofcoursenotpossibletogivethetimeargu- ment,butyoucanenteraexplanatorymessageonthecommandlinethatwillbesenttoallusers. timeWhentoshutdown. warning-message Messagetosendtoallusers. Thetimeargumentcanhavedifferentformats.First,itcanbeanabsolutetimeintheformathh:mm,inwhich hhisthehour(1or2digits)andmmistheminuteofthehour(intwodigits).Second,itcanbeinthefor- mat+m,inwhichmisthenumberofminutestowait.Thewordnowisanaliasfor+0. Ifshutdowniscalledwithadelay,itcreatestheadvisoryfile/etc/nologinwhichcausesprogramssuchas login(1)tonotallownewuserlogins.Shutdownremovesthisfileifitisstoppedbeforeitcansignalinit (i.e.itiscancelledorsomethinggoeswrong).Italsoremovesitbeforecallinginittochangetherunlevel. The-fflagmeans鈥榬ebootfast鈥?Thisonlycreatesanadvisoryfile/fastbootwhichcanbetestedbythesys- temwhenitcomesupagain.Thebootrcfilecantestifthisfileispresent,anddecidenottorunfsck(1) sincethesystemhasbeenshutdownintheproperway.Afterthat,thebootprocessshouldremove/fastboot. The-Fflagmeans鈥榝orcefsck鈥?Thisonlycreatesanadvisoryfile/forcefsckwhichcanbetestedbythesys- temwhenitcomesupagain.Thebootrcfilecantestifthisfileispresent,anddecidetorunfsck(1)with aspecial鈥榝orce鈥?flagsothatevenproperlyunmountedfilesystemsgetchecked.Afterthat,thebootprocess shouldremove/forcefsck. The-nflagcausesshutdownnottocallinit,buttokillallrunningprocessesitself.shutdownwillthen turnoffquota,accounting,andswappingandunmountallfilesystems. ACCESSCONTROL shutdowncanbecalledfrominit(8)whenthemagickeysCTRL-ALT-DELarepressed,bycreatinganappropriate entryin/etc/inittab.Thismeansthateveryonewhohasphysicalaccesstotheconsolekeyboardcanshutthe systemdown.Topreventthis,shutdowncanchecktoseeifanauthorizeduserisloggedinononeofthevir- tualconsoles.Ifshutdowniscalledwiththe-aargument(addthistotheinvocationofshutdownin/etc/init- tab),itcheckstoseeifthefile/etc/shutdown.allowispresent.Itthencomparestheloginnamesinthat filewiththelistofpeoplethatareloggedinonavirtualconsole(from/var/run/utmp).Onlyifoneofthose authorizedusersorrootisloggedin,itwillproceed.Otherwiseitwillwritethemessage shutdown:noauthorizedusersloggedin tothe(physical)systemconsole.Theformatof/etc/shutdown.allowisoneusernameperline.Emptylinesand commentlines(prefixedbya#)areallowed.Currentlythereisalimitof32usersinthisfile. Notethatif/etc/shutdown.allowisnotpresent,the-aargumentisignored. HALTORPOWEROFF The-HoptionjustsetstheinitenvironmentvariableINIT_HALTtoHALT,andthe-Poptionjustsetsthatvari- abletoPOWEROFF.Theshutdownscriptthatcallshalt(8)asthelastthingintheshutdownsequenceshould checktheseenvironmentvariablesandcallhalt(8)withtherightoptionsfortheseoptionstoactuallyhave anyeffect.Debian3.1(sarge)supportsthis. FILES /fastboot /etc/inittab /etc/init.d/halt /etc/init.d/reboot /etc/shutdown.allow NOTES Alotofusersforgettogivethetimeargumentandarethenpuzzledbytheerrormessageshutdownproduces. Thetimeargumentismandatory;in90percentofallcasesthisargumentwillbethewordnow. InitcanonlycaptureCTRL-ALT-DELandstartshutdowninconsolemode.IfthesystemisrunningtheXwindow System,theXserverprocessesallkeystrokes.SomeX11environmentsmakeitpossibletocaptureCTRL-ALT-DEL, butwhatexactlyisdonewiththateventdependsonthatenvironment. Shutdownwasn鈥檛designedtoberunsetuid./etc/shutdown.allowisnotusedtofindoutwhoisexecutingshut- down,itONLYcheckswhoiscurrentlyloggedinon(oneofthe)console(s). AUTHOR MiquelvanSmoorenburg,miquels@cistron.nl SEEALSO fsck(8),init(8),halt(8),poweroff(8),reboot(8) November12,2003SHUTDOWN(8) (END)
2：马上关闭Linux系统，其中now相当于时间为0的状态
[root@db-server~]#shutdown-hnow Broadcastmessagefromroot(pts/1)(SatJan1018:51:342015): ThesystemisgoingdownforsystemhaltNOW!
3：系统2分钟后重新启动，其中+m表示几分钟后关机或开机。
[root@db-server~]#shutdown-r+2 Broadcastmessagefromroot(pts/2)(SatJan1019:56:002015): ThesystemisgoingDOWNforrebootin2minutes!
4：设置系统在那个时间点关机
[root@db-server~]#shutdown-h12:30
或
[root@db-server~]#shutdown-h12:30& [1]4578
最好是使用命令&将关机命令至于后台处理。不影响当前其它操作。
设置多久时间后执行shutdown命令。时间参数有hh：mm或+m两种模式。hh：mm格式表示在几点几分执行shutdown命令。例如“shutdown10：45”表示将在10：45执行shutdown.+m表示m分钟后执行shutdown.比较特别的用法是以now表示立即执行shutdown.值得注意的是这部分参数不能省略。另外，需要注意如果现在已经22:30，你执行了shutdown-h22:00&那么第二天才会关机。
5：将前一个shutdown命令取消息
如下所示，执行了下面命令让Linux在12:30关机，但是如果发现这个时间点不合适，那么可以使用CTRL+C取消
[root@db-server~]#shutdown-h12:30 Shutdowncancelled. [root@db-server~]#
也可以在另外一个命令窗口执行下面命令
[root@db-server~]#shutdown-c
6：向所有登录的用户发出信息
[root@db-server~]#shutdown-k"now" Broadcastmessagefromroot(pts/2)(SatJan1020:09:142015): ThesystemisgoingdowntomaintenancemodeNOW! Shutdowncancelled.
另外登录的会话窗口会收到如下信息
[root@db-server~]# [root@db-server~]# Broadcastmessagefromroot(pts/2)(SatJan1020:11:342015): ThesystemisgoingdowntomaintenancemodeNOW!
一般使用下面语法，如下所示
[root@db-server~]#shutdown-know"TheServerwillshutdownnow" Broadcastmessagefromroot(pts/1)(SatJan1020:14:542015): TheServerwillshutdownnow ThesystemisgoingdowntomaintenancemodeNOW! Shutdowncancelled.
7：重新启动时不进行磁盘检测
[root@db-server~]#shutdown-frnow Broadcastmessagefromroot(pts/1)(SatJan1020:23:592015): ThesystemisgoingdownforrebootNOW!
8：在多少秒后关闭系统并给用户发送提示信息
[root@db-server~]#shutdown-t10-hnow"Systemwillshutdown10sencondlater" Broadcastmessagefromroot(pts/1)(SatJan1020:33:362015): Systemwillshutdown10sencondlater ThesystemisgoingdownforsystemhaltNOW!
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