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I would like to create a glance image from a running nova instance, and am able to do so with

nova image-create instance-id new-image-name

However, the created image is huge. It appears to be the same size as the disk from the instance's flavor (~150gb) instead of close to the size of the instance's original image (2-3gb).

I found some documentation that seems to have a warning about creating images without associated kernel and ramdisk images not being resizable on boot, but I'm not sure how to I would go about creating an image from and existing instance that has associated kernel and ramdisk images.

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Is the image thick provisioned? If so, you're basically out of luck on that. You could probably use a drive cloning tool to clone the drive to another "virtual" disk. dd can accomplish that. – Nathan C Jun 7 '13 at 11:35
How do I know if the image is thick provisioned? Perhaps you can expand on why I'd be out of luck if that's the case. – mmrobins Jun 10 '13 at 17:48
"Thick" provisioned is the non-sparse configuration which means the space is occupied immediately rather than a slow-growing file. If it's thick provisioned then it'll be much larger than the space it's taking up, as you're seeing. Note that I'm not really an openstack expert so hopefully one will stop by this thread. :-) – Nathan C Jun 10 '13 at 17:54

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