引言
一个业务压测要进行非正常关机，如何模拟呢？
这让我首先重新去深入理解 Linux 系统中的几个关机命令（shutdown/halt）。
shutdown
man shutdown:
shutdown arranges for the system to be brought down in a safe way. All logged-in users are notified that the system is going down and, within the last five minutes of TIME, new logins are prevented.
从上面的说明可以看到，shutdown 是一个安全的正常关机的命令。
以下是来自网友详细一点 shutdown 过程的说明：
shutdown -h now will call /etc/rc.d/rc or /etc/init.d/rc. The rc script will call the kill scripts for the new runlevel (0 for -h, 6 for -r), followed by any start scripts. You'll see S30killprocs or S00killall or something like that depending on your distro. This comes after all the kill scripts have been called to attempt to stop each service gracefully in turn. It will try kill -15 first, followed by kill -9. Short answer: shutdown -h now or shutdown -r now are graceful.
reboot/halt/poweroff
我们首先要看下这 3 个命令所处路径：
[root@Aliyun-BJ-01 ~]# ll /sbin/halt /sbin/reboot /sbin/poweroff lrwxrwxrwx. 1 root root 6 Aug 14 2014 /sbin/halt -> reboot lrwxrwxrwx. 1 root root 6 Aug 14 2014 /sbin/poweroff -> reboot -rwxr-xr-x. 1 root root 14832 Mar 12 2014 /sbin/reboot
上面是在 CentOS 系统下，可以看到 halt/poweroff 命令实际是指向 reboot 命令的软链接。
所以我们man reboot/man halt/man poweroff会得到相同的结果
These programs allow a system administrator to reboot, halt or poweroff the system. When called with --force or when in runlevel 0 or 6, this tool invokes the reboot(2) system call itself and directly reboots the system. Otherwise this simply invokes the shutdown(8) tool with the appropriate arguments. -f, --force Does not invoke shutdown(8) and instead performs the actual action you would expect from the name.
从上面可以看出不带 -f 选项，则就会调用 shutdown 命令执行正常重启或关机，
如果带 -f 选项就是强制直接重启或关机，非正常关机应该可以这样模拟。
群里一朋友说了另一个简单的方法：kill -9 1，直接强制杀掉 init 进程，这个应该也算是非正常关机。
总结
模拟非正常关机/重启的方法：
