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Date:      Tue, 2 Feb 1999 09:45:51 -0800 (PST)
From:      David Wolfskill <dhw@whistle.com>
To:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: more modular rc/init/uninit system...
Message-ID:  <199902021745.JAA16874@pau-amma.whistle.com>
In-Reply-To: <36B6ADB3.6D6F5247@newsguy.com>

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>Date: Tue, 02 Feb 1999 16:48:03 +0900
>From: "Daniel C. Sobral" <dcs@newsguy.com>

>The suggestion was to have each service's script know what depends
>on it.

And it seems to me that this is backwards (because it becomes a
maintenance issue).

Consider Makefile dependencies:  we list, for a given target, what that
target depends on.

Similarly, the given script should be able to say (if invoked with, for
example, a "-dependencies" argument) what services it needs to be up in
order to run.  (A list echoed to standard output would seem ideal.)

Thus, given a list of services to be brought up, it would be possible to
ask each one what its list of dependencies is, and perform transitive
closure on the list.

It may be useful to cache the information in a file; in the usual case,
I would expect it to be rare for a services dependencies to change
unless one of the scripts in the (transitive closure of the) set of
scripts needed to start it up has changed.  (In the rare case where that
is not the case, merely invalidate the cache.  If the cache is
implemented as a normal file, unlinking it should do the job rather
effectively.)

david
-- 
David Wolfskill		UNIX System Administrator
dhw@whistle.com		voice: (650) 577-7158	pager: (650) 371-4621

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