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Re: OVF vs. bare container formats for qcow2 images

 

On Wed, Mar 28, 2012 at 04:41:28PM -0400, Lorin Hochstein wrote:
> All:
> 
> Given that I have a qcow2 image from somewhere (e.g., downloaded
> it from a 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
image.

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

> 2. Why does it matter?

OVF provides metadata that is useful to virt/cloud mgmt applications
when deploying a prebuilt disk image.  I've no idea what use OpenStack
makes of the OVF metadata though.

> 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:

  http://uec-images.ubuntu.com/precise/current/precise-server-cloudimg-amd64-disk1.img

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

  http://uec-images.ubuntu.com/precise/current/precise-server-cloudimg-amd64.ovf


Sometimes, people may create a zip/tar.gz file that contains both the
disk image and OVF file in one convenient download.

Regards,
Daniel
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