系统初始化过程是指从INIT进程成功启动，一直到系统启动并弹出登录提示之间的过程。当INIT进程成功启动后，，它会根据配置文件/etc/inittab中的设置初始化系统，这个过程主要完成的工作有：重新挂载文件系统、运行系统需要的进程和服务等。
一、INIT进程的配置文件
INIT进程的配置文件是/etc/inittab，这个配置文件会引导INIT进程初始化系统，开启必要的进程、服务等。
查看inittab内容如下：
[root@localhost ~]# cat /etc/inittab## inittabThis file describes how the INIT process should set up#the system in a certain run-level.## Author:Miquel van Smoorenburg, <miquels@drinkel.nl.mugnet.org>#Modified for RHS Linux by Marc Ewing and Donnie Barnes## Default runlevel. The runlevels used by RHS are:# 0 – halt (Do NOT set initdefault to this)# 1 – Single user mode# 2 – Multiuser, without NFS (The same as 3, if you do not have networking)# 3 – Full multiuser mode# 4 – unused# 5 – X11# 6 – reboot (Do NOT set initdefault to this)# #设置系统默认的运行级别id:5:initdefault:#初始化系统脚本# System initialization.si::sysinit:/etc/rc.d/rc.sysinit#启动系统服务l0:0:wait:/etc/rc.d/rc 0l1:1:wait:/etc/rc.d/rc 1l2:2:wait:/etc/rc.d/rc 2l3:3:wait:/etc/rc.d/rc 3l4:4:wait:/etc/rc.d/rc 4l5:5:wait:/etc/rc.d/rc 5l6:6:wait:/etc/rc.d/rc 6#定义Ctrl+Alt+Delete键的作用# Trap CTRL-ALT-DELETEca::ctrlaltdel:/sbin/shutdown -t3 -r now#设置电源选项# When our UPS tells us power has failed, assume we have a few minutes# of power left. Schedule a shutdown for 2 minutes from now.# This does, of course, assume you have powerd installed and your# UPS connected and working correctly. pf::powerfail:/sbin/shutdown -f -h +# If power was restored before the shutdown kicked in, cancel it.pr:#启动终端# Run gettys in standard runlevels1:2345:respawn:/sbin/mingetty tty12:2345:respawn:/sbin/mingetty tty23:2345:respawn:/sbin/mingetty tty34:2345:respawn:/sbin/mingetty tty45:2345:respawn:/sbin/mingetty tty56:2345:respawn:/sbin/mingetty tty6# Run xdm in runlevel 5x:5:respawn:/etc/X11/prefdm -nodaemon没有什么可凭仗，只有他的好身体，没有地方可去，
