Bug 1119929 - virt-manager creates qcow3 image instead of qcow2
virt-manager creates qcow3 image instead of qcow2
Product: Fedora
Classification: Fedora
Component: virt-manager (Show other bugs)
x86_64 Linux
unspecified Severity medium
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Assigned To: Cole Robinson
Fedora Extras Quality Assurance
Depends On:
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Reported: 2014-07-15 17:24 EDT by Hayley Hudgeons
Modified: 2014-07-16 17:40 EDT (History)
4 users (show)

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Doc Type: Bug Fix
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Clone Of:
Last Closed: 2014-07-16 17:39:33 EDT
Type: Bug
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RHEL 7.3 requirements from Atomic Host:
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Description Hayley Hudgeons 2014-07-15 17:24:03 EDT
Description of problem:
An image was created in virt-manager with the default format set to qcow2 for new images. After trying to use that image in openstack I found that the image is actually a qcow3 image. I am unable to convert from qcow3 to qcow2 because qemu-img doesn't recognize qcow3.

Version-Release number of selected component (if applicable):

How reproducible:
Everytime a new image is created when qcow2 is set as default, it creates a qcow2 image. 

Steps to Reproduce:
1. Set virt-manager prefs so new images are qcow2
2. Create and install a new VM from ISO
3. Run file against the .qcow2 image that is created, and it will show that it is qcow3

Actual results:
A qcow3 image is created:

# file rhel6_sat6.qcow2 
rhel6_sat6.qcow2: QEMU QCOW Image (v3), 8589934592 bytes

Expected results:
I except that this would create a qcow2 image, or at the very least that I could convert it with the latest version of qemu-img

Additional info:
Comment 1 Shanzhi Yu 2014-07-15 21:45:38 EDT
I can convert qcow2v3 to qcow2v2 with latest qemu-img

# rpm -q qemu-img

# qemu-img convert -f qcow2 /var/lib/libvirt/images/qcow2v3.img -O qcow2 -o compat=0.10 /var/lib/libvirt/images/qcow2v2.img 

# file /var/lib/libvirt/images/qcow2v2.img
/var/lib/libvirt/images/qcow2v2.img: QEMU QCOW Image (v2), 1073741824 bytes

Should qemu-img-1.6.2-6.fc20.x86_64 can also do that.
Comment 2 Cole Robinson 2014-07-16 17:39:33 EDT
Yes, virt-manager/virt-install on Fedora 20 by default create images that won't run on RHEL6. It's a pain, but we need to extra features to get acceptable snapshot performance.

See Shanzhi's suggestion for conversion:

> # qemu-img convert -f qcow2 /var/lib/libvirt/images/qcow2v3.img -O qcow2 -o
> compat=0.10 /var/lib/libvirt/images/qcow2v2.img 

Indeed that should work on F20 qemu 1.6 as well. However it will discard any internal qcow2 snapshots, so beware.

(qemu-img etc. don't have an explicit qcow3 version, it's just qcow2 + compat options. The 'QCOW Image (v3)' comes from the qcow2 header, I wish it didn't say that though since it's misleading).
Comment 3 Cole Robinson 2014-07-16 17:40:00 EDT
Also see this mail for more details:


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