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Date:      Thu, 6 Sep 2001 16:54:30 -0500
From:      Mike Meyer <mwm@mired.org>
To:        Salvo Bartolotta <bartequi@neomedia.it>
Cc:        Mike Meyer <mwm@mired.org>, Ceri <ceri@techsupport.co.uk>, questions@freebsd.org
Subject:   Re: Good practice for /tmp
Message-ID:  <15255.61590.455896.440737@guru.mired.org>
In-Reply-To: <999807502.3b97da0e9af9f@webmail.neomedia.it>
References:  <999807502.3b97da0e9af9f@webmail.neomedia.it>

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Salvo Bartolotta <bartequi@neomedia.it> types:
> > An mfs is supposedly backed by swap. So if swap is on mfs, what's
> > backing the mfs? Is the inverse of the dual the dual of the inverse?
> > Where's the tylenol?
> Hmm, the dual of a dual is isomorphic to the original space. :-)

But the dual of a graph may not be a graph.

> > Anyway, I agree with you. Putting swap on mfs or md seems sort of
> > pointless. If the goal is to prevent people from reading sensitive
> > information left on swap if the hardware is compromised - which is
> > something security people do worry about - just configure the system
> > without any swap.
> I am probably missing something here. I seem to understand that even systems 
> with a *large* amount of RAM [occasionally] make use of swap; in other words, 
> the OS seems to be tuned to utilize swap, regardless of the amount of RAM 
> present on the machine.

While it's certainly correct that the system runs better with swap - a
minimum of 256MB is recommended by tuning(7) - that doesn't mean it
absolutely has to have any swap at all.

> Enlightenment welcome :-)

During the install process, the system clearly runs without swap -
which is one of the reasons you have to have more memory to install
FreeBSD than you do to use it. The comments in LINT about the
NO_SWAPPING option indicate that it's expected that a system can run
that way.

If you believe pstat -s, I just booted and ran a system sans swap by
the simple expedient bring it up single user, removing the swap
partition from /etc/fstab, and then going multi-user. No problems -
but I was careful not to do anything that would use lots of memory.

	<mike
--
Mike Meyer <mwm@mired.org>			http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

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