[Kimchi-devel] [RFC] Guest cloning

[Christy Perez]

I'm guessing that Brent and Adam already discussed virt-clone, so I'm
curious as to the reasons why that's not an option. I've found that
virt-install (the package that includes it) has (on Fedora 20) a
dependency on virt-manager-common. That, and maybe it's not available
for all distros? Maybe it wouldn't copy disks into the right places?

Thanks,

- Christy

On 10/06/2014 08:28 AM, Crístian Viana wrote:
> On Sex, 2014-10-03 at 08:28 -0500, Brent Baude wrote:
>> At one point Adam had really suggested we look at how guests are defined
>> and changed.  In particular, straight copies of XML and or straight
>> edits of XML could lead (after time) to the XML digressing into
>> something libvirt might not understand at some point.  
> 
> Do you remember exactly what in the XML file digressed like that? It
> would be very nice to know it.
> 
>> To prevent this sort of problem, we thought that each time a guest is
>> edited, the XML is created entirely anew but of course using the same
>> values.
> 
> I first thought about doing that as well, but I'm afraid our own new XML
> does not have all the features the original VM had. For example, on
> Kimchi we don't have support to custom CPU flags yet (i.e. we don't
> add/change those values). What would happen if we clone an existing VM
> with "unsupported" (as of Kimchi) features like that one? If we don't
> know about them and we're creating a new XML from scratch, we're only
> going to add what we're aware of. And I think this could make our
> cloning feature very unrealiable. Reading an existing XML and redefining
> it will always propagate whatever there is in that VM. As long as the
> XML doesn't get digressed, of course.
> 
> Here's one current scenario for me. I have a few VMs on my laptop which
> I use to test Kimchi on them. As they need to be a hypervisor in order
> to run Kimchi, I have to add a few CPU flags to their XML descriptors
> which allow them to be a hypervisor (i.e. those Intel/AMD virtualization
> parameters). I do that manually using "virsh edit". If I clone one of my
> VMs using the approach above and it recreates their XML files from the
> beginning, AFAIU, the CPU flags will not be copied along. And I'd be
> very unsatisfied because the clone feature dropped a few things of my
> original VM while cloning.
> 
> If we know what are the problems you had with Adam while copying the XML
> files over and over, maybe it' easier to fix them than to try to create
> a new one with all the libvirt's features, including the ones Kimchi is
> still not aware of.
> 
>> About a month ago I had a working version of this in draft
>> form.
>> Would anyone be interested in reviewing it and or adding to it prior to
>> implementing the clone function?  If so, ping me on IRC and I'll get you
>> a copy of the patch.
> 
> I am interested on it! I'll ping you then.
>