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 [-t sec] [-arkhncfFHP] time [warning-message]

命令参数：

参数

长参数

描叙

-a

Use /etc/shutdown.allow.

-c

中断关机：当执行"shutdown -h 12:00"指令时，只要按+键就可以中断关机的指令

-f

重新启动时不进行磁盘检测（fsck）

-F

重新启动时进行磁盘检测（fsck）

-h

关闭电源

-k

模拟关机（不是真的关机），只是向登录者发送警告信息出去！

-n

不调用init进程进行关机，而是强行关机

-r

关闭系统然后重新启动，类似于Windows平台restart

-t

延迟关机的时间

-w

仅做测试，并不真的将系统重新开机，只会把重开机的数据写入/var/log目录下的wtmp记录文件

--help

显示命令在线帮助

使用示例：

1: 查看reboot命令的帮助信息

[root@db-server ~]# shutdown --helpshutdown: 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 shutdownSHUTDOWN(8)      Linux System Administrator 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 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 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 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    login(1) to not allow new user logins. Shutdown removes this file if it is stopped before it can signal init    (i.e. it is cancelled or something goes wrong). It also removes it before calling init to change the runlevel.     The -f flag means eboot fast? 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 orce fsck? 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 orce?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 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 SEE ALSO    fsck(8), init(8), halt(8), poweroff(8), reboot(8)                 November 12, 2003          SHUTDOWN(8)(END)