== _/etc/inittab_ versus _/etc/rc.d_

One aspect of [[yesterday's problem DispellingNightmare]] is a little
ordering issue between _/etc/inittab_ and stuff in _/etc/rc.d_. Namely:

> Everything in _/etc/rc.d_ runs before other things in _/etc/inittab_
> really takes effect.

(The paths here are for Red Hat; elsewhere, what Red Hat puts in
_/etc/rc.d_ is just put straight into _/etc_, so you have _/etc/init.d_
and _/etc/rc3.d_ and so on.)

Normally the only effect this has is things like being able to log
in via ssh well before you can log in on the console. In the case
yesterday, the machine had one QMail listener being started via
_rc.local_ as part of the regular _rcN.d_ startup scripts, and another
one being started through Dan Bernstein's _svcscan_ system that's kicked
off directly from a line in _/etc/inittab_; the former won, to my
confusion when I was looking at the latter.

(The _init_ and _inittab_ documentation doesn't really say what order
_/etc/inittab_ entries are run in, but I suspect that in the order they
occur in the file is not a bad assumption. The lines that run the system
startup scripts are usually very early in _inittab_.)

Reading _/etc/inittab_ and following everything there can be interesting
in general. Almost all of the bits and pieces are shell scripts, and it
really gives you an understanding of just what the system does when.
(And every so often it's useful to know the commands to force a poweroff
or reboot *right now*.)