rc-default task and inittab

Under SysVinit, the initdefault entry in the /etc/inittab file tells init which runlevel) to bring the system to when it comes up. Ubuntu does not include an inittab file and, by default, the Upstart init daemon (using the rc-default task) boots the system to multiuser mode (runlevel 2, the default runlevel). If you want the system to boot to a different runlevel, create an inittab file. The following file causes the system to boot to single-user mode (runlevel S):

$ cat /etc/inittab
:id:S:initdefault:

verified on ubuntu 8.04