linux运行级别halt 0-6

[root@oldboylinux ~/test]#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)无网络多用户模式
#   3 - Full multiuser mode 有网络多用户模式
#   4 - unused  未使用
#   5 - X11  有网络支持有X-Window支持的多用户模式
#   6 - reboot (Do NOT set initdefault to this) 重新引导系统，即重启
# 
id:3:initdefault:
[root@oldboylinux ~/test]#

/etc/inittab 中有定义

0 关机

1 单用户

2 无网络多用户

3 有网络多用户

4 未使用

5 有网络支持有X-Window支持的多用户模式

6 - reboot (Do NOT set initdefault to this) 重新引导系统，即重启