Libguestfs - May 2016 - Re: Can I specify qcow2 preallocation method with virt-builder?

When creating qcow2 images using virt-builder, is there a way to specify
the qcow2 preallocation, as possible with qemu-img create -o
preallocation=metada , for example?

TIA,
Y.

On Tue, May 17, 2016 at 05:15:57PM +0300, Yaniv Kaul
wrote:
> When creating qcow2 images using virt-builder, is there a way to specify
> the qcow2 preallocation, as possible with qemu-img create -o
> preallocation=metada , for example?
No .. but .. it does default to preallocation=metadata provided that
the output format is qcow2:

https://github.com/libguestfs/libguestfs/blob/master/builder/builder.ml#L582-L585
https://github.com/libguestfs/libguestfs/blob/master/src/create.c#L281-L295

Rich.

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On Tue, May 17, 2016 at 03:41:53PM +0100, Richard W.M. Jones
wrote:
> On Tue, May 17, 2016 at 05:15:57PM +0300, Yaniv Kaul wrote:
> > When creating qcow2 images using virt-builder, is there a way to
specify
> > the qcow2 preallocation, as possible with qemu-img create -o
> > preallocation=metada , for example?
> 
> No .. but .. it does default to preallocation=metadata provided that
> the output format is qcow2:
> 
>
https://github.com/libguestfs/libguestfs/blob/master/builder/builder.ml#L582-L585
I should say this only applies when the image needs to be resized
(ie. you supply a --size parameter which != the size of the template),
AND if the resize is the final step that the planner comes up with.

https://rwmj.wordpress.com/2013/12/14/writing-a-planner-to-solve-a-tricky-programming-optimization-problem/

In the general case implementing this is more complicated.  I think it
would require another planner transition.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top