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Date:      Sun, 17 Jul 2011 08:32:06 +0200
From:      Polytropon <freebsd@edvax.de>
To:        Aryeh Friedman <aryeh.friedman@gmail.com>
Cc:        FreeBSD Mailing List <freebsd-questions@freebsd.org>
Subject:   Re: how to force a hard reboot remotely
Message-ID:  <20110717083206.db111314.freebsd@edvax.de>
In-Reply-To: <CAGBxaXnz3cD6ZKaDiDW_YEWpdhwjkAUBLM07T0_2NkpGc5QfmA@mail.gmail.com>
References:  <CAGBxaXnz3cD6ZKaDiDW_YEWpdhwjkAUBLM07T0_2NkpGc5QfmA@mail.gmail.com>

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On Sat, 16 Jul 2011 22:40:19 -0400, Aryeh Friedman wrote:
> Is there any way to force a complete power down and then reset of a
> i386 without physically being present?

I'm not fully sure what you mean by "reset" in terms
that it happens _after_ powering down. When a machine
is powered down (i. e. switched off), it's "implicitely"
a reset - compare to pressing the RESET button which
will keep the system powered on, but will perform a
(very hard) reset.

Allow me to point you to the following manpages:

	man shutdown

	man reboot

	man init

A problem will be: How to power a machine back on that
has been powered off?

I assume you don't want the hard reset, you want to
perform a clean shutdown first, followed by a powering
down, and THEN power the machine back up.

That's quite easy, although you need something more than
just onboard means.

I may introduce a (quite stupid) solution I "invented" many
years ago: Prior to performing the "shutdown -p <time>"
command, you access one of the parallel port's lines in
order to start a timer (a quite basic transistor + relay
is sufficient). This timer runs at least as long as the
shutdown needs in average. Let's assume the shutdown
needs (including all timeouts and wait states) 5 minutes.
After those 5 minutes, the timer generates a "pressing"
of the machine's power button, which means it will power
on again.

It's comparable to C. E. Shannon's "Ultimate Machine" in
some regards. :-)

Of couse, this approach can be used even to switch on
AT systems which (unlike ATX) have a real power switch.
This switch is then replaced by a self-supporting relay
system that can be externally triggered (as those systems
can't reflect the -p option of shutdown, just -h is
possible).

I hope this is a little inspiration about what's possible
if you're willing to get your hands dirty. :-)

-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...



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