linux的shutdown命令详解

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linux的shutdown命令详解

linux下关机我们可以采用shutdown命令来实现，下面由店铺为

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linux的shutdown命令详解

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

-a

-c

长参数

描叙

Use /etc/.

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

重新启动时不进行磁盘检测（fsck）

重新启动时进行磁盘检测（fsck）

关闭电源

模拟关机（不是真的关机），只是向登录者发送警告信息出

去！

不调用init进程进行关机，而是强行关机

关闭系统然后重新启动，类似于Windows平台restart

延迟关机的时间

-f

-F

-h

-k

-n

-r

-t

-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

显示命令在线帮助

--help

linux的shutdown命令使用示例

1: 查看reboot命令的帮助信息

[root@db-server ~]# shutdown --help

shutdown: invalid option -- -

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

message]

-a: use /etc/

-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/.

-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

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 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/ 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/ 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/ 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/

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/ 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

MiquelvanSmoorenburg,******************

SEE ALSO

fsck(8), init(8), halt(8), poweroff(8), reboot(8)

November 12, 2003 SHUTDOWN(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 -h now

Broadcast message from root (pts/1) (Sat Jan 10 18:51:34

2015):

The system is going down for system halt NOW!

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

Broadcast message from root (pts/2) (Sat Jan 10 19:56:00

2015):

The system is going DOWN for reboot in 2 minutes!

4：设置系统在那个时间点关机

[root@db-server ~]# shutdown -h 12:30

或

[root@db-server ~]# shutdown -h 12:30 &

[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 “shutdown 10：45”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 -h 22:00 & 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 -h 12:30

Shutdown cancelled.

[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"

Broadcast message from root (pts/2) (Sat Jan 10 20:09:14

2015):

The system is going down to maintenance mode NOW!

Shutdown cancelled.

另外登录的会话窗口会收到如下信息

[root@db-server ~]#

[root@db-server ~]#

Broadcast message from root (pts/2) (Sat Jan 10 20:11:34

2015):

The system is going down to maintenance mode NOW!

一般使用下面语法，如下所示

[root@db-server ~]# shutdown -k now "The Server will

shutdown now"

Broadcast message from root (pts/1) (Sat Jan 10 20:14:54

2015):

The Server will shutdown now

The system is going down to maintenance mode NOW!

Shutdown cancelled.

7：重新启动时不进行磁盘检测

[root@db-server ~]# shutdown -fr now

Broadcast message from root (pts/1) (Sat Jan 10 20:23:59

2015):

The system is going down for reboot NOW!

8：在多少秒后关闭系统并给用户发送提示信息

[root@db-server ~]# shutdown -t 10 -h now "System will

shutdown 10 sencond later"

Broadcast message from root (pts/1) (Sat Jan 10 20:33:36

2015):

System will shutdown 10 sencond later

The system is going down for system halt NOW!

本文标签： 命令关机执行时间信息