[CentOS-devel] The status of our Vagrant images for Hyper-V

Laurentiu Pancescu

lpancescu at gmail.com
Mon Apr 10 15:13:51 UTC 2017


On 10/04/17 16:57, Michael Vermaes wrote:
> On Fri, Apr 7, 2017 at 7:51 PM, Laurentiu Pancescu <lpancescu at gmail.com> wrote:
>> I would prefer the second option, using VBoxManage to produce small
>> non-sparse .VHD images for our Vagrant boxes, and avoid the compatibility
>> problems posed by sparse files.  But this would need to be done in Image
>> Factory, so it's actually for Ian to decide if using VirtualBox is
>> acceptable.
> 
> After using qemu-img to convert the qcow2 image to VHD and then
> extracting the resulting tar file on the Hyper V host, the resulting
> image was back to being 40GB 'non-sparse'.
> 
> Using VBoxManage instead, 'vagrant up' time was reduced to be
> comparable to the kozo/centos7 box: [snip]
> So I would also say the second option is the way to go if possible :)

qemu-img has several options for the vpc and vhdx formats ("qemu-img 
convert -O vpc -o ?" will show them).  Earlier today I tried all 
possible combinations of subformat, preallocation and block_state_zero, 
without any visible effect: it always produces sparse files for vpc 
(.vhd) and huge non-sparse file for .vhdx.

qemu-img seems to be right to produce sparse .vhd files, if I correctly 
understand the documentation from libvhdi. [1]  VirtualBox doesn't, but 
what they're doing seems to work better in practice.

[1] 
https://github.com/libyal/libvhdi/blob/master/documentation/Virtual%20Hard%20Disk%20(VHD)%20image%20format.asciidoc#4-block-table

Any thoughts about using VBoxManage to convert the images to .vhd? 
VirtualBox supports neither .vhdx nor QCOW2, so we'd need to convert via 
.vmdk or another format.



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