Confused about connection between an option in rc.conf and the associated action?

[Giorgos Keramidas]

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On 2005-03-13 02:49, Ola Theander <ola.theander at otsystem.com> wrote:
> Dear subscribers
>
> I'm slightly confused about enabling an option in rc.conf and the associated
> action? E.g. say that I enable gateway_enable="YES" or maybe
> dhcpd_enable="YES", how does FreeBSD associate this simple line to the
> associated action? I've had a theory that adding e.g. test_enable="YES" to
> rc.conf would trigger the execution of the file /etc/rc.d/test.sh at boot
> time but it seems like this isn't how it's done.

The /etc/rc script is the first "rc script" that runs.  This is the one
that takes care of running all the rest of the rc stuff.

In pre-5.X versions of FreeBSD, the /etc/rc script called a predefined
set of /etc/rc.* scripts at specific points during the startup process,
delegating pieces of the work to them.

In 5.3-RELEASE and later versions of FreeBSD, there is a collection of
small /etc/rc.d/* scripts, that are called by /etc/rc instead of the
older /etc/rc.* stuff.  The specific order these scripts will have is
determined at boot time, by the /sbin/rcorder utility.

Each script, either one of the older /etc/rc.* stuff or the newer
/etc/rc.d/* scripts, slurps in /etc/rc.conf and then checks what parts
of the script are enabled to run.  It is the responsibility of the
specific script to check the proper rc.conf variables and act
accordingly.

A small example of an rc script that checks a variable and modifies its
own behavior is /etc/rc.d/tmp, which contains (among other stuff):

    load_rc_config $name

    # If we do not have a writable /tmp, create a memory
    # filesystem for /tmp.  If /tmp is a symlink (e.g. to /var/tmp,
    # then it should already be writable).
    #
    case "${tmpmfs}" in
    [Yy][Ee][Ss])
	    ...

Thus, it's not /etc/rc that checks the "tmpfs" variable from rc.conf,
but the specific script that is interested in its value.

Regards,

Giorgos