where is etc inittab equivalent ?

[Tapas Mishra]

I searched a file /etc/inittab in Ubuntu 10.04 bit bit.
It was not there.
On some link found Ubuntu stopped using that 3 years before.

Searching some blogs forums found
/etc/events.d
above directory was missing on my system.

checked /etc/rc.local
did not found what I was looking at.
Also looked at /etc/init.d/rc.local
but could not find the desired entry.

What I am trying to find out is how do Ubuntu decides which run level
is default?
Which file contains that entry?