[Openstack] Qcow2 Details on base images

Jay Pipes jaypipes at gmail.com
Thu Aug 2 17:23:34 UTC 2012


On 08/02/2012 07:47 AM, Gaurab Basu wrote:
> Hi Jay,
> 
> Thanks for your reply, it helped me get started.
> 
> I have been going through the code and some of the sparse docs that are
> available.
> 
> This is the code file
> https://github.com/openstack/nova/blob/master/nova/virt/libvirt/utils.py
> 
> However I am facing a new issue and require some help. I wanted to
> modify how openstack handles the cow layer as such and also the qcow2
> format.
> It turns out that openstack issues the external command "qemu-img".
> 
> First of all, is qemu-img internal to openstack ( I mean code for how
> qemu-img is implemented is in openstack or in qemu )
> It is in openstack, where is the code located.
> 
> If it is outside openstack, does that mean i have to change the code in
> qemu and then link those binaries with openstack.

QEMU is a totally separate project from Nova, yes. QEMU is written in C
and has a number of executables such as qemu-img and qemu-nbd, etc. Nova
calls out to these executables in subprocesses.

If you want to make changes to QEMU, yes, you would want to look into
the QEMU contribution process and community.

Here's where to start:

http://wiki.qemu.org/Documentation/GettingStartedDevelopers

Best,
-jay




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