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Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images? |
Date: |
Mon, 28 May 2018 22:25:10 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, May 28, 2018 at 10:20:54PM +0100, Richard W.M. Jones wrote:
> 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
I should add the other thorny issue with OVA files is that the
metadata contains a checksum (SHA1 or SHA256) of the disk images. If
you modify the disk images in-place in the tar file then you need to
recalculate those.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, (continued)
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Max Reitz, 2018/05/28
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Richard W.M. Jones, 2018/05/28
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Kevin Wolf, 2018/05/28
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Max Reitz, 2018/05/28
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Kevin Wolf, 2018/05/28
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Max Reitz, 2018/05/29
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Kevin Wolf, 2018/05/29
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Eduardo Habkost, 2018/05/29
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Richard W.M. Jones, 2018/05/28
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?,
Richard W.M. Jones <=
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Kevin Wolf, 2018/05/29
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Max Reitz, 2018/05/29