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

[Ola Theander]

Hello Giorgos and everybody else

Thank you for your answers. It clarified things a bit but there is still a
few things that I don't understand. Say I want to create my own script that
should run depending on the setting in rc.conf:

- Do I need to parse rc.conf myself in the script or is rc.conf parsed once
and for all by rcorder (or someone else) and the settings are available e.g.
as environment variables? 

- How is my own script found and executed by the rc script? Does the rc
script execute all *.sh files in the /etc/rc.d/ directory or is some other
mechanism used?

- Must the config string in rc.conf have any correspondence to the actual
script file using it? E.g. if I add a setting test_enable="YES" my script
must be named test.sh?

- This last question is somewhat related to the first. Say that I don't have
to parse rc.conf myself, which variable name to I test in my script for the
rc.conf setting? E.g. if I have a config string in rc.conf named
test_enable="YES", how do I test for this variable's value? Do I use
"test_enable" == "YES" or do I use "test" == "YES", i.e. the "_enable" part
may be stripped by the parser?

BTW I use FreeBSD 5.3.

Kind regards, Ola Theander

-----Original Message-----
From: Giorgos Keramidas [mailto:keramida at ceid.upatras.gr] 
Sent: den 13 mars 2005 03:14
To: Ola Theander
Cc: freebsd-questions at freebsd.org
Subject: Re: Confused about connection between an option in rc.conf and the
associated action?

# Redirected from freebsd-newbies to freebsd-questions.
# Please do not post technical questions to freebsd-newbies.
# This is what freebsd-questions is for.  Followups set.

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