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Re: OVF vs. bare container formats for qcow2 images


On 04/01/2012 11:15 AM, Lorin Hochstein wrote:

On Mar 29, 2012, at 12:40 PM, Daniel P. Berrange wrote:

On Wed, Mar 28, 2012 at 04:41:28PM -0400, Lorin Hochstein wrote:

Given that I have a qcow2 image from somewhere (e.g., downloaded
it from a uec-images.ubuntu.com <http://uec-images.ubuntu.com>, created one from a raw image using
qemu-img) that i want to add to glance:

1. How can I tell whether it's an "ovf" or "bare" container format?

You are mixing up terminology here. Disk image formats are things like
raw, qcow2, vmdk, etc.

OVF refers to the format of a metadata file provided alongside the
disk image, which describes various requirements for running the

The two are not tied together at all, merely complementary to
each other.

Thanks, that clears things up. I was confused by this language, which sounded to me like the metadata was embedded in the disk image file:


"The container format refers to whether the virtual machine image is in a file format that also contains metadata about the actual virtual machine."

In addition, the docs have examples like this, which clearly aren't meaningful:

Just to add to the confusion the OVF can contain both the metadata file and the disk image file in a single archived file.

"An OVF package consists of several files, placed in one directory. A one-file alternative is the OVA package, which is a TAR file with the OVF directory inside."


I think that what you are reading above refers to the single file alternative.

$> glance add name="My Image" is_public=true \
      container_format=ovf disk_format=raw < /tmp/images/myimage.iso

I'll propose a change to the docs for that.

Whenever I add a qcow2 image to glance, I always choose "ovf",
even though it's probably "bare", because I saw an example
somewhere, and it just works, so I keep doing it. But I don't
know how to inspect a binary file to determine what its container
is (if "file image.qcow2" says it's a QEMU QCOW2 Image (v2), does
that mean it's "bare"?). In particular, why does the user need to
specify this information?

If you simply have a single  someimage.qcow2 file, then you simply
have a disk image. Thus there is no OVF metadata involved at all.

eg, this is the (qcow2) disk image:


While this is an OVF metadata file that optionally accompanies the disk image



It's not clear to me how you would specify the OVF metadata file when adding an image file to glance.

Take care,

Lorin Hochstein
Lead Architect - Cloud Services
Nimbis Services, Inc.
www.nimbisservices.com <https://www.nimbisservices.com/>

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