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init
首先看看LINUX系统几种运行级别
# 0 - 停机（千万别把initdefault设置为0，否则系统永远无法启动）
# 1 - 单用户模式
# 2 - 多用户，没有 NFS
# 3 - 完全多用户模式(标准的运行级)
# 4 – 系统保留的
# 5 - X11 （x window)
# 6 - 重新启动 （千万不要把initdefault 设置为6，否则将一直在重启 ）
#init 0 切换到运行级别0
动作为运行如下两个脚本：
[root@limt rc0.d]# pwd /etc/rc.d/rc0.d [root@limt rc0.d]# ls -lrt S* lrwxrwxrwx. 1 root root 14 Jun 16 2013 S01halt -> ../init.d/halt lrwxrwxrwx. 1 root root 17 Jun 16 2013 S00killall -> ../init.d/killall
#init 6 切换到运行级别6
动作为运行如下两个脚本：
[root@limt rc6.d]# pwd /etc/rc.d/rc6.d [root@limt rc6.d]# ls -lrt S* lrwxrwxrwx. 1 root root 14 Jun 16 2013 S01reboot -> ../init.d/halt lrwxrwxrwx. 1 root root 17 Jun 16 2013 S00killall -> ../init.d/killall
shutdown
shutdown - bring the system down shutdown [OPTION]... TIME [MESSAGE] -r Requests that the system be rebooted after it has been brought down. -h Requests that the system be either halted or powered off after it has been brought down, with the choice as to which left up to the system. -H Requests that the system be halted after it has been brought down. -P Requests that the system be powered off after it has been brought down. -c Cancels a running shutdown. TIME is not specified with this option, the first argument is MESSAGE. -k Only send out the warning messages and disable logins, do not actually bring the system down.
#shutdown -r 等同reboot，它在系统关闭之前给系统上的所有登录用户提示一条警告信息，然后调用init 6 #shutdown -H 等同halt 它在系统关闭之前给系统上的所有登录用户提示一条警告信息，然后调用init 0 #shutdown -P 等同poweroff 它在系统关闭之前给系统上的所有登录用户提示一条警告信息，然后调用init 0
reboot,poweroff,halt
reboot,poweroff,halt实际为一个命令，后两者为reboot的链接
[root@limt rc0.d]# ls -lrt /sbin/reboot -rwxr-xr-x. 1 root root 14832 3月 20 2012 /sbin/reboot [root@limt rc0.d]# ls -lrt /sbin/poweroff lrwxrwxrwx. 1 root root 6 6月 16 2013 /sbin/poweroff -> reboot [root@limt rc0.d]# ls -lrt /sbin/halt lrwxrwxrwx. 1 root root 6 6月 16 2013 /sbin/halt -> reboot
不带--force参数的reboot实际是调用shutdown名，带--force参数的reboot直接关机
init shutdown reboot poweroff halt区别
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原文地址：http://www.cnblogs.com/limt/p/4247980.html
