Re: [kvm-devel] [Qemu-devel] Re: [PATCH] Add support for a configuration file

[Daniel P. Berrange]

On Wed, May 14, 2008 at 06:01:43PM +0200, Andreas F?rber wrote:
> 
> Am 14.05.2008 um 17:30 schrieb Javier Guerra:
> 
> >personally, i find shell scripts enough for setting up parameters.  a
> >static config wouldn't bring much advantages.
> 
> For personal use they are okay, but for distributing a machine, you  
> may need two or three platform-specific scripts for QEMU, or even  
> worse one config file per frontend.
> 
> VMware has the advantage of allowing to distribute one .vmx file along  
> with the image to facilitate its use. QEMU users can be happy if a raw  
> or qcow2 image is provided at all and then need to figure out useful  
> command line parameters (and whether to use qemu or qemu-system-x86_64  
> or whichever).

Re-distribution of virtual machine images is a problem that's tangential
to configuration file. 

There is alot of data you want in the configuration file for a specific
deployment of a VM, that is simply not relevant or desired when distributing
appliances. As such you don't typically want to simply distribute the config
file. Furthermore, the format for distributing appliances can & shouuld be
independant of the virtualization technology used for a specific deployment.

So an appliance format would specify *requirements*, eg a virtualization
product capable of fully virtualizing a x86_64 CPU.  The tool to deploy
an instace of the appliance examines the requirements to decide hwo to
satisfy them, eg it might decide qemu-system-x86_64 will do, or it might
decide to use  'kvm' instead. 

You simply do not want to tie the deployment configuration to the metadata
for redistribution. It happened to more or less work for VMWare with VMDK
and VMX file, only because VMWare were the only game in town with no real
widely deployed alternatives. That time has passed.

Dan.
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