Bug 1204131

Summary:	RFE: virt-builder creates qcow v3 images, add build option for qcow v2
Product:	[Community] Virtualization Tools	Reporter:	Stefan Assmann <sassmann>
Component:	libguestfs	Assignee:	Richard W.M. Jones <rjones>
Status:	CLOSED NEXTRELEASE	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	unspecified	CC:	mbooth, ptoscano, rbalakri, rjones, virt-maint
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-11-04 10:17:07 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Stefan Assmann 2015-03-20 13:00:05 UTC

Description of problem:
When building an image in qcow format with
virt-builder centos-7.0 --format qcow --hostname centos-7.0
the output format will be qcow v3, which is not supported for example in centos6.

Would be nice to have a compat option for qcow v2, something like
virt-builder centos-7.0 --format qcowv2 --hostname centos-7.0

Pointer to qcow compat format info
https://lists.fedoraproject.org/pipermail/virt/2014-April/004041.html

So virt-builder could use something like
qemu-img convert -f raw <file.img> -O qcow2 -o compat=0.10 <file.qcow>

Version-Release number of selected component (if applicable):
libguestfs-tools-c-1.28.6-1.fc21.x86_64

Comment 1 Richard W.M. Jones 2015-03-20 13:26:31 UTC

Although it would be nice for virt-builder to be able to create
these directly, I will note there is a qemu-img amend command you
can use to downgrade the image (assuming that the image doesn't already
use certain modern features).

$ virt-builder centos-7.0 --format qcow2
$ qemu-img amend -f qcow2 -o compat=0.10 centos-7.0.qcow2 
$ qemu-img info centos-7.0.qcow2 
image: centos-7.0.qcow2
file format: qcow2
virtual size: 6.0G (6442450944 bytes)
disk size: 943M
cluster_size: 65536
Format specific information:
    compat: 0.10               <--- note

For more details see
https://bugzilla.redhat.com/show_bug.cgi?id=1033490

There is also a bug about adding compat=1.1 support for RHEL 6, but
I cannot find it right now.

Comment 2 Richard W.M. Jones 2015-11-04 10:17:07 UTC

After looking at this, I think the best (and certainly the simplest)
approach is just to document the 'qemu-img amend' command, and
that is the patch I have posted:

https://www.redhat.com/archives/libguestfs/2015-November/msg00023.html

The only problem with this is that the qemu-img amend command won't
run on RHEL 6 itself (you have to run it on RHEL 7), but then again
virt-builder doesn't run on RHEL 6 either.

This fix will appear in 1.31.24.