/etc  存放各种配置文件

•    /etc/inittab   控制启动模式              

       [root@localhost ~]# cat /etc/inittab

  # inittab is only used by upstart for the default runlevel.

  #

  # ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.

  #

  # System initialization is started by /etc/init/rcS.conf

  #

  # Individual runlevels are started by /etc/init/rc.conf

  #

  # Ctrl-Alt-Delete is handled by /etc/init/control-alt-delete.conf

  #

  # Terminal gettys are handled by /etc/init/tty.conf and /etc/init/serial.conf,

  # with configuration in /etc/sysconfig/init.

  #

  # For information on how to write upstart event handlers, or how

  # upstart works, see init(5), init(8), and initctl(8).

  #

  # Default runlevel. The runlevels used are:

  #   0 - halt (Do NOT set initdefault to this)（关机）

  #   1 - Single user mode （单用户模式）

  #   2 - Multiuser, without NFS (The same as 3, if you do not have networking) （多用户模式）

  #   3 - Full multiuser mode （命令行模式）

  #   4 - unused （没有使用）

  #   5 - X11  （桌面模式）

  #   6 - reboot (Do NOT set initdefault to this)（重启）

  # id:3:initdefault:

1. 查看运行级别
   

   [root@localhost ~]# runlevel

   N 3

2. 不同模式切换

   init 数字

linux文件存放目录详解