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Date: Mon, 3 Nov 2008 11:04:22 -0600
From: Matt <datahead4@gmail.com>
To: "Marc G. Fournier" <scrappy@hub.org>
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Cc: freebsd-questions@freebsd.org
Subject: Re: copying 'holey' files ...
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On Mon, Nov 3, 2008 at 10:40 AM, Marc G. Fournier <scrappy@hub.org> wrote:
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
>
> I have a disk img for qemu that is 4G, but disk usage is only 650M ... due to
> how the image is created, it will grow to 4G, but only uses as much as it needs
> ... but, if I run a simple 'cp' on the file, it goes from:
>
> image: debian.img
> file format: raw
> virtual size: 4.0G (4294967296 bytes)
> disk size: 652M
>
> to:
>
> image: dtc.img
> file format: raw
> virtual size: 4.0G (4294967296 bytes)
> disk size: 4.0G
>
> Is there a way of moving things around such that it *maintains* the holes,
> instead of fills them in?
>
The "qemu-img" program using the "convert" command should do what you
want it to.  I've used it to make copies of qcow-format disks without
having them grow to their max-size.

Matt