Subject: Re: Changing root's shell to /bin/sh
To: None <jonathan@DSG.Stanford.EDU>
From: maximum entropy <firstname.lastname@example.org>
Date: 03/17/1999 14:43:14
>cc: email@example.com, firstname.lastname@example.org, email@example.com
>Date: Wed, 17 Mar 1999 11:04:42 -0800
>From: Jonathan Stone <jonathan@DSG.Stanford.EDU>
>yes. but this amounts to running a `make' over the list of
>dependencies at every boot (possibly changing nothing if the dependencies
It doesn't need to be that complex. The decision-making process
doesn't need to know about dependencies, it just needs to determine if
the configuratioon has changed. What I had in mind is more like:
# this is only a sample, not intended to be a real implementation
# of course it would really need to be written in C, both for speed
# and because cmp is in /usr/bin...
ls -l /etc/rc.d > /etc/rc.d.files.new
cmp /etc/rc.d.files.new /etc/rc.d.files
if [ $? -ne 0 ]
smart-program-to-rebuild-configuration > /etc/rc.d.run.new
if [ $? -eq 0 ]
mv /etc/rc.d.run.new /etc/rc.d.run
mv /etc/rc.d.files.new /etc/rc.d.files
``smart-program-to-rebuild-configuration'' would read all the
"require" and "provide" information from the scripts in /etc/rc.d, and
produce the startup script that would call all of them in the correct
order. The decision-making process would be fast -- either the
configuration has changed or it hasn't.
>iirc, some developers objected fairly fiercely to that idea (not using
>make, but the idea of depending on the dependency-checker, crashes
>halfway through the `atomic' dependency-file update, etc, etc.).
Why is this different from a crash halfway through /etc/rc or
/etc/rc.conf? The example given above would cause it to continue with
the old configuration. Or it could just as easily drop out to single
user mode so you can fix it.
>Would it be a useful first step to take the existing monolithic
>/etc/rc, and break that up into sensible `modules'?
>While leaving all the rc.conf machinery alone?
Maybe, but it might be difficult to determine what's sensible without
an implementation to test it against.
entropy -- it's not just a good idea, it's the second law.