linux的shutdown命令詳解

時間：2017-07-14 09:39:32 佳洲1085由分享

linux的shutdown命令詳解

　　linux下關機我們可以采用shutdown命令來實現，下面由學習啦小編為大家搜集整理了linux的shutdown命令詳解的相關知識，希望對大家有幫助!

　　linux的shutdown命令詳解

　　命令簡介：

　　該命令可以安全關閉或者重新啟動系統。你沒有看錯，shutdown命令不僅可以關閉系統、也可以重啟Linux系統。

　　命令語法：

　　/sbin/shutdown [-t sec] [-arkhncfFHP] time [warning-message]

　　命令參數：

參數	長參數	描敘
-a		Use /etc/shutdown.allow.
-c		中斷關機：當執行"shutdown -h 12:00"指令時，只要按+鍵就可以中斷關機的指令
-f		重新啟動時不進行磁盤檢測（fsck）
-F		重新啟動時進行磁盤檢測（fsck）
-h		關閉電源
-k		模擬關機（不是真的關機），只是向登錄者發送警告信息出去！
-n		不調用init進程進行關機，而是強行關機
-r		關閉系統然后重新啟動，類似于Windows平臺restart
-t		延遲關機的時間
-w		僅做測試，并不真的將系統重新開機，只會把重開機的數據寫入/var/log目錄下的wtmp記錄文件
	--help	顯示命令在線幫助

　　linux的shutdown命令使用示例

　　1: 查看reboot命令的幫助信息

　　[root@db-server ~]# shutdown --help

　　shutdown: invalid option -- -

　　Usage: shutdown [-akrhHPfnc] [-t secs] time [warning message]

　　-a: use /etc/shutdown.allow

　　-k: don't really shutdown, only warn.

　　-r: reboot after shutdown.

　　-h: halt after shutdown.

　　-P: halt action is to turn off power.

　　-H: halt action is to just halt.

　　-f: do a 'fast' reboot (skip fsck).

　　-F: Force fsck on reboot.

　　-n: do not go through "init" but go down real fast.

　　-c: cancel a running shutdown.

　　-t secs: delay between warning and kill signal.

　　** the "time" argument is mandatory! (try "now") **

　　[root@db-server ~]#

　　[root@db-server ~]# man shutdown

　　SHUTDOWN(8) Linux System Administrator鈥檚 Manual SHUTDOWN(8)

　　NAME

　　shutdown - bring the system down

　　SYNOPSIS

　　/sbin/shutdown [-t sec] [-arkhncfFHP] time [warning-message]

　　DESCRIPTION

　　shutdown brings the system down in a secure way. All logged-in users are notified that the system is going

　　down, and login(1) is blocked. It is possible to shut the system down immediately or after a specified delay.

　　All processes are first notified that the system is going down by the signal SIGTERM. This gives programs like

　　vi(1) the time to save the file being edited, mail and news processing programs a chance to exit cleanly, etc.

　　shutdown does its job by signalling the init process, asking it to change the runlevel. Runlevel 0 is used to

　　halt the system, runlevel 6 is used to reboot the system, and runlevel 1 is used to put to system into a state

　　where administrative tasks can be performed; this is the default if neither the -h or -r flag is given to shut-

　　down. To see which actions are taken on halt or reboot see the appropriate entries for these runlevels in the

　　file /etc/inittab.

　　OPTIONS

　　-a Use /etc/shutdown.allow.

　　-t sec Tell init(8) to wait sec seconds between sending processes the warning and the kill signal, before

　　changing to another runlevel.

　　-k Don鈥檛 really shutdown; only send the warning messages to everybody.

　　-r Reboot after shutdown.

　　-h Halt or poweroff after shutdown.

　　-H Halt action is to halt or drop into boot monitor on systems that support it.

　　-P Halt action is to turn off the power.

　　-n [DEPRECATED] Don鈥檛 call init(8) to do the shutdown but do it ourself. The use of this option is dis-

　　couraged, and its results are not always what you鈥檇 expect.

　　-f Skip fsck on reboot.

　　-F Force fsck on reboot.

　　-c Cancel an already running shutdown. With this option it is of course not possible to give the time argu-

　　ment, but you can enter a explanatory message on the command line that will be sent to all users.

　　time When to shutdown.

　　warning-message

　　Message to send to all users.

　　The time argument can have different formats. First, it can be an absolute time in the format hh:mm, in which

　　hh is the hour (1 or 2 digits) and mm is the minute of the hour (in two digits). Second, it can be in the for-

　　mat +m, in which m is the number of minutes to wait. The word now is an alias for +0.

　　If shutdown is called with a delay, it creates the advisory file /etc/nologin which causes programs such as

　　(i.e. it is cancelled or something goes wrong). It also removes it before calling init to change the runlevel.

　　The -f flag means 鈥榬eboot fast鈥? This only creates an advisory file /fastboot which can be tested by the sys-

　　tem when it comes up again. The boot rc file can test if this file is present, and decide not to run fsck(1)

　　since the system has been shut down in the proper way. After that, the boot process should remove /fastboot.

　　The -F flag means 鈥榝orce fsck鈥? This only creates an advisory file /forcefsck which can be tested by the sys-

　　tem when it comes up again. The boot rc file can test if this file is present, and decide to run fsck(1) with

　　a special 鈥榝orce鈥?flag so that even properly unmounted filesystems get checked. After that, the boot process

　　should remove /forcefsck.

　　The -n flag causes shutdown not to call init, but to kill all running processes itself. shutdown will then

　　turn off quota, accounting, and swapping and unmount all filesystems.

　　ACCESS CONTROL

　　shutdown can be called from init(8) when the magic keys CTRL-ALT-DEL are pressed, by creating an appropriate

　　entry in /etc/inittab. This means that everyone who has physical access to the console keyboard can shut the

　　system down. To prevent this, shutdown can check to see if an authorized user is logged in on one of the vir-

　　tual consoles. If shutdown is called with the -a argument (add this to the invocation of shutdown in /etc/init-

　　tab), it checks to see if the file /etc/shutdown.allow is present. It then compares the login names in that

　　file with the list of people that are logged in on a virtual console (from /var/run/utmp). Only if one of those

　　authorized users or root is logged in, it will proceed. Otherwise it will write the message

　　shutdown: no authorized users logged in

　　to the (physical) system console. The format of /etc/shutdown.allow is one user name per line. Empty lines and

　　comment lines (prefixed by a #) are allowed. Currently there is a limit of 32 users in this file.

　　Note that if /etc/shutdown.allow is not present, the -a argument is ignored.

　　HALT OR POWEROFF

　　The -H option just sets the init environment variable INIT_HALT to HALT, and the -P option just sets that vari-

　　able to POWEROFF. The shutdown script that calls halt(8) as the last thing in the shutdown sequence should

　　check these environment variables and call halt(8) with the right options for these options to actually have

　　any effect. Debian 3.1 (sarge) supports this.

　　FILES

　　/fastboot

　　/etc/inittab

　　/etc/init.d/halt

　　/etc/init.d/reboot

　　/etc/shutdown.allow

　　NOTES

　　A lot of users forget to give the time argument and are then puzzled by the error message shutdown produces.

　　The time argument is mandatory; in 90 percent of all cases this argument will be the word now.

　　Init can only capture CTRL-ALT-DEL and start shutdown in console mode. If the system is running the X window

　　System, the X server processes all key strokes. Some X11 environments make it possible to capture CTRL-ALT-DEL,

　　but what exactly is done with that event depends on that environment.

　　Shutdown wasn鈥檛 designed to be run setuid. /etc/shutdown.allow is not used to find out who is executing shut-

　　down, it ONLY checks who is currently logged in on (one of the) console(s).

　　AUTHOR

　　Miquel van Smoorenburg, miquels@cistron.nl

linux的shutdown命令詳解

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