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Date:      Wed, 6 Aug 1997 18:35:27 +0930 (CST)
From:      Greg Lehey <grog@lemis.com>
To:        jamil@counterintelligence.ml.org (Jamil J. Weatherbee)
Cc:        hackers@freebsd.org (FreeBSD Hackers)
Subject:   Re: Hot Swappable Kernels
Message-ID:  <199708060905.SAA05837@freebie.lemis.com>
In-Reply-To: <Pine.BSF.3.96.970806004529.266A-100000@counterintelligence.ml.org> from "Jamil J. Weatherbee" at "Aug 6, 97 00:56:38 am"

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Jamil J. Weatherbee writes:
>
> I know this may sound kind of lame:
>
> I was thinking last night of what would be required to have a hot
> swappable kernel.. i.e. being able to compile the kernel binary (probably)
> modules and then insert it into a running system while maintaining its
> running status --- to my knowledge kernel recompiles are the only reason a
> perfectly rebooting system needs to come down every once in a while.

I suspect people are going to shoot you down in flames, and they're
probably justified.  But I suppose you'd like to know that I've done
just that in the past, at Tandem.  The operating system is a loosely
coupled network, so we were able to boot one machine at a time.
Despite the obvious interest of such a scheme for Tandem, and despite
my extensive lobbying, it never came to anything.

I can't imagine how you would start to do such a thing with UNIX.  The
closest you could come to it would be to split most of the kernel into
LKMs, and change them.  But there's a basic conflict of concept
between keeping a kernel running (even if it's no longer the same
kernel) and booting a kernel.

Greg



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