linux里有几种启动级别,而且改动系统的启动级别实在inittab文件里
# Default runlevel. The runlevels used by RHS are:
# 0 - halt (Do NOT set initdefault to this)//关机
# 1 - Single user mode//单用户模式(可以改root密码)
# 2 - Multiuser, without NFS (The same as 3, if you do not have networking)//多用户模式
# 3 - Full multiuser mode
# 4 - unused//保留
# 5 - X11//xwindows
# 6 - reboot (Do NOT set initdefault to this)//重启