Re: Exporting qcow2 images as raw data from ova file with qemu-nbd

[Nir Soffer]

On Fri, Jun 26, 2020 at 11:34 PM Richard W.M. Jones <rjones@redhat.com> wrote:
>
> On Fri, Jun 26, 2020 at 10:42:02PM +0300, Nir Soffer wrote:
> > Can we have better support in qemu-img/qemu-nbd for accessing images
> > in a tar file?
> >
> > Maybe something like:
> >
> >     qemu-img info tar://vm.ova?member=fedora-32.qcow2
>
> Isn't this exactly a case where nbdkit-tar-plugin would work despite
> the performance problems with it being written in Python?  Something like:
>
> $ tar tvf disk.ova
> -rw-r--r-- rjones/rjones 2031616 2020-06-26 21:32 disk.qcow2
>
> $ nbdkit -U - tar tar=disk.ova file=disk.qcow2 --run 'qemu-img info 
> --output=json $nbd'
> {
>     "virtual-size": 105923072,
>     "filename": "nbd+unix://?socket=/tmp/nbdkitTjkeRd/socket",
>     "cluster-size": 65536,
>     "format": "qcow2",
>     "format-specific": {
>         "type": "qcow2",
>         "data": {
>             "compat": "1.1",
>             "lazy-refcounts": false,
>             "refcount-bits": 16,
>             "corrupt": false
>         }
>     },
>     "dirty-flag": false
> }
>
> qemu-img measure will work the same way.

Looks like format probing just works this way, I'll try this, thanks!

Nir