设置运行级别
查看开机加载级别：7个级别 规范场景默认都是3
cat /etc/inittab --> 系统开机启动加载的文件，可以设置运行级别
# Default runlevel. The runlevels used are:··:反引号，tab之上
# 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 (没有用的模式)
# 5 - X11 (桌面模式)
# 6 - reboot (Do NOT set initdefault to this)
id:3:initdefault:
查看当前的运行级别[默认就是3]：runlevel
切换运行级别
init 5 (切换桌面模式)
==>startx