关闭和启动系统例如；
shutdown -h now //立即关闭系统
shutdown -h 45 //45min 后关闭系统
shutdown -r now "system will bereboot now!" //发出通告，并重新启动
shutdown
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 run-
level.
-k Don’t really shutdown; only sendthe warning messages to every-
body.
-r Reboot after shutdown. //关机后立即重启
-h Halt or poweroff after shutdown.//关机后不重新启动
-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’t call init(8) to do the shutdown but doit
ourself. The use of this option is discouraged, andits results
are not always what you’d expect.//快速关机，不经过init程序
-f Skip fsck on reboot. //快速关机，重启时跳过fsck
-F Force fsck on reboot.
-c Cancel an already running shutdown. With this option it is of
course not possible to give thetime argument, but you can enter
a explanatory message on thecommand line that will be sent to
all users. //取消一个已经运行的shutdown
time When to shutdown. //设定关机前的时间
Halt
//引发主机关机操作
OPTIONS
-n Don’t sync before reboot or halt. Note that the kernel and stor-
age drivers may still sync.
-w Don’t actually reboot or halt but only write the wtmp record (in
the /var/log/wtmp file).
-d Don’t write the wtmp record. The -n flag implies -d.
-f Force halt or reboot, don’t call shutdown(8).
-i Shut down all network interfaces just before halt or reboot.
-h Put all harddrives on the system in standby modejust before
halt or poweroff.
-p When halting the system, do a poweroff. This is the default when
halt is called as poweroff.
Reboot
//引发主机重启操作
系统重启
Init
init 0 为关机
init 1 为重启
