[CentOS] Xen, Amazon, and /proc/cmdline

Amazon (or perhaps Amazon's configuration of Xen) forces a machine to
come up at run level 4, regardless of what's in /etc/inittab.

I've looked through /etc/rc.sysinit and /etc/rc.d/rc, to determine which
(if any script) looks at /proc/cmdline and forces a particular run
level, but to no avail.

It seems that /sbin/init does the forcing.  Can anyone confirm that
/sbin/init reads /proc/cmdline to overwrite /etc/inittab?  I can't seem
to find any reference in man pages or searching the web.

Thanks,
Kurt