Linux命令之shutdown

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shutdown命令安全地将系统关机。 有些用户会使用直接断掉电源的方式来关闭linux,这是十分危险的。因为linux与windows不同,其后台运行着许多进程,所以强制关机可能会导致进程的数据丢失﹐使系统处于不稳定的状态﹐甚至在有的系统中会损坏硬件设备。可用man shutdown来了解命令的详细使用。

SHUTDOWN(8)                                      shutdown                                     SHUTDOWN(8)

NAME
       shutdown - Halt, power-off or reboot the machine

SYNOPSIS
       shutdown [OPTIONS...] [TIME] [WALL...]

DESCRIPTION
       shutdown may be used to halt, power-off or reboot the machine.

       The first argument may be a time string (which is usually "now"). Optionally, this may be followed
       by a wall message to be sent to all logged-in users before going down.

       The time string may either be in the format "hh:mm" for hour/minutes specifying the time to
       execute the shutdown at, specified in 24h clock format. Alternatively it may be in the syntax "+m"
       referring to the specified number of minutes m from now.  "now" is an alias for "+0", i.e. for
       triggering an immediate shutdown. If no time argument is specified, "+1" is implied.

       Note that to specify a wall message you must specify a time argument, too.

       If the time argument is used, 5 minutes before the system goes down the /run/nologin file is
       created to ensure that further logins shall not be allowed.

OPTIONS
       The following options are understood:

       --help
           Print a short help text and exit.

       -H, --halt
           Halt the machine.

       -P, --poweroff
           Power-off the machine (the default).

       -r, --reboot
           Reboot the machine.

       -h
           Equivalent to --poweroff, unless --halt is specified.

       -k
           Do not halt, power-off, reboot, just write wall message.

       --no-wall
           Do not send wall message before halt, power-off, reboot.

       -c
           Cancel a pending shutdown. This may be used cancel the effect of an invocation of shutdown
           with a time argument that is not "+0" or "now".

EXIT STATUS
       On success, 0 is returned, a non-zero failure code otherwise.

SEE ALSO
       systemd(1), systemctl(1), halt(8), wall(1)

systemd 229                                                                                   SHUTDOWN(8)

从man page可知道:shutdown被用来暂停、关闭、重启机器。shutdown后面有3个参数,都是有[],说明都是可选参数。在DESCRIPTION里了解到,如果未指定TIME参数,那就意味着默认配置“+1”,单位为分钟。如果TIME参数为now,那就意味着时间配置为“+0”,单位为分钟。时间也可设置为"hh:mm" = hour/minutes进行操作。

命令参数说明:

--help:帮助
-H/--half:关闭机器
-P/--poweroff:关闭机器
-r/--reboot:重启机器
-h:与--poweroff一样
-k:不暂停、不关闭、不重启机器,只发送消息给在线的用户
--no-wall:暂停、关闭、重启机器前,不发送消息给在线的用户
-c:取消shutdown命令操作

实例:

特定时间执行关机命令

shutdown –h now             //立即关机
shutdown –h 12:00           //在12:00关机

指定五分钟后关机,并发出警告信息

shutdown +5 “This System will be shutdown in 5 minutes”
Broadcast message from [email protected]8(/dev/pts/0) at 13:33 …
 
The system is going down for maintenance in 5 minutes!                 //系统提醒
This System will be shutdown in 5 minutes                              //用户自定义提醒

指定3分钟后重启,并发出警告信息

shutdown –r +3 “3分钟后关机重启”
Broadcast message from [email protected]8(/dev/pts/0) at 13:53 …
 
The system is going down for reboot in 3 minutes!          //系统提醒
3分钟后关机重启                                              //用户自定义提醒

给所有登录用户发送提醒,不关闭重启。

[[email protected] 桌面]# shutdown –k 5 “Waring:maybe the system will be shutdown”
[[email protected] 桌面]#
Broadcast message from [email protected]8(/dev/pts/0) at 14:26 …
 
The system is going down for maintenance in 5 minutes!
Waring:maybe the system will be shutdown

 

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