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

[Richard W.M. Jones]

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.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org