Re: [Qemu-devel] storing machine data in qcow images?

[Richard W.M. Jones]

On Mon, May 28, 2018 at 08:38:33PM +0200, Kevin Wolf wrote:
> Just accessing the image file within a tar archive is possible and we
> could write a block driver for that (I actually think we should do
> this), but it restricts you because certain operations like resizing
> aren't really possible in tar. Unfortunately, resizing is a really
> common operation for non-raw image formats.

We do this already in virt-v2v (using file.offset and file.size
parameters in the raw driver).

For virt-v2v we only need to read the source so resizing isn't an
issue.  For most of the cases we're talking about the downloaded image
would also be a template / base image, so I suppose only reading would
be required too.

I also wrote an nbdkit tar file driver (supports writes, but not
resizing).
https://manpages.debian.org/testing/nbdkit-plugin-perl/nbdkit-tar-plugin.1.en.html

Rich.

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