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Date: Mon, 30 Apr 2001 23:04:41 +0200
From: Andreas Ferber <aferber@techfak.uni-bielefeld.de>
To: "Richard B. Johnson" <root@chaos.analogic.com>
Cc: "David S. Miller" <davem@redhat.com>,
        Torrey Hoffman <torrey.hoffman@myrio.com>,
        "'Kenneth Johansson'" <ken@canit.se>,
        Jonathan Lundell <jlundell@pobox.com>, linux-kernel@vger.kernel.org
Subject: Re: 2.4 and 2GB swap partition limit
Message-ID: <20010430230441.A12723@kallisto.sind-doof.de>
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	"David S. Miller" <davem@redhat.com>,
	Torrey Hoffman <torrey.hoffman@myrio.com>,
	'Kenneth Johansson' <ken@canit.se>,
	Jonathan Lundell <jlundell@pobox.com>, linux-kernel@vger.kernel.org
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In-Reply-To: <Pine.LNX.3.95.1010430151259.15968A-100000@chaos.analogic.com>; from root@chaos.analogic.com on Mon, Apr 30, 2001 at 03:14:25PM -0400
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Hi,

On Mon, Apr 30, 2001 at 03:14:25PM -0400, Richard B. Johnson wrote:

> > mv /wherever/exeimage /usr/bin/exeimage
[...]
> > This is also basically how things like libc get installed.
> > A single mv is not only preserves currently referenced contents,
> > it is atomic.

One restriction: /wherever and /usr/bin must be on the same partition,
otherwise the mv will be the same as "rm /usr/bin/exeimage && cp
/wherever/exeimage /usr/bin/exeimage && rm /wherever/exeimage", which
is for sure not atomic.

> Sure, but now you can't get back if the new software doesn't run.
> This is why I recommended the two steps and cautioned about testing
> the new stuff first.

Then create a hardlink first, to keep a backup _and_ atomically
replace the file.

Andreas
-- 
Build a system that even a fool can use and only a fool will want to use it.

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