启动级别:
init 0,1,2,3,4,5,6 这是个很久的知识点了，只是自己一直都迷迷糊糊的，今天在翻出来好好理解下。。
- 0: 停机
- 1：单用户形式，只root进行维护
- 2：多用户，不能使用net file system
- 3：完全多用户
- 4：安全模式
- 5：图形化
- 6：重启
编辑 /etc/inittab 文件，可以修改系统默认启动级别
[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)
# 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)
#
id:5:initdefault:
[root@localhost ~]#