[Kimchi-devel] [RFC] Guest cloning

[Christy Perez]

On 10/07/2014 11:29 AM, Aline Manera wrote:
> 
> On 10/07/2014 12:27 PM, Christy Perez wrote:
>> 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?
> 
> It was what I had in mind.
> We could investigate on how virt-manager and virt-clone do it.

Also - FWIW, virt-install is available on PowerKVM as well as RHEL and
Fedora.

> 
>> 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.
>>>
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>