Can the linux shutdown command shut down immediately?

The Linux shutdown command shutdown can shut down the system immediately. The root user only needs to execute the "shutdown -h now" command. The shutdown command can be used to perform the shutdown process and send messages to all programs being executed by users before shutting down. The shutdown command requires the system administrator root user to use it.

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

The Linux shutdown command shutdown can shut down the computer immediately.

Linux commands to shut down immediately are:

• shutdown -h now Shut down immediately (for root users)

• halt Shut down immediately

• poweroff Shut down immediately

If If you set the shutdown through the shutdown command, you can use the shutdown -c command to cancel the restart

linux shutdown command introduction

The Linux shutdown command can be used to perform the shutdown process and send messages to all programs being executed by the user before shutting down. The shutdown command can also be used to restart the computer.

Usage permissions: System administrator.

grammar

shutdown [-t seconds] [-rkhncfF] time [message]

##Parameter Description：

• ##-t seconds: set after a few seconds Perform the shutdown procedure.
• -k: It does not actually shut down the computer, it just sends a warning message to all users.
• -r : Shut down and then restart.
• #-h : Stop after shutdown.
• #-n: Instead of using normal procedures to shut down, forcefully kill all running programs and then shut down automatically.
• #-c : Cancel the shutdown action currently in progress.
• -f: When shutting down, do not perform fcsk action (check Linux file system).
• #-F: Force fsck action when shutting down.
• #time: Set the shutdown time.
• #message: Warning message sent to all users.

Example

Shut down immediately

# shutdown -h now

Specify shutdown after 10 minutes

# shutdown -h 10

Restart the computer

# shutdown -r now

Command syntax:

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

命令参数：

示例：
1：马上关闭Linux系统，其中 now 相当于时间为 0 的状态示例：

# shutdown -h now

2：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

3：设置系统在那个时间点关机

# shutdown -h 12:30

或后台执行 

# shutdown -h 12:30 &

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。

4：查看后台是否执行shutdown命令

# jobs
[1]+ Running shutdown -h 08:00 &

5：取消shutdown命令执行

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。

# shutdown -h 12:30
Shutdown cancelled.

也可以在另外一个命令窗口执行下面命令

# shutdown -c

6：向所有登录的用户发出信息

# 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!

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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		Delay shutdown time
##-w		# It’s just for testing, it doesn’t really restart the system, it only writes the restarted data The wtmp record file in the /var/log directory
	##--help	Display command online help

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