On Wed, 29 Aug 2012 08:53:51 +0100, Invisible wrote:

>>>> Or if it's a base for multiple linked clones where you started from a
>>>> common base, but the clones are different.
>>>
>>> Then wouldn't each clone have its own local cloned disk image?
>>
>> Again, no.  That's not what a linked clone is.
>>
>> I might be inclined to suggest "RTFM", as the VirtualBox and VMware
>> documentation both describe what a linked clone is.  Rather than assume
>> what it is and then make statements based on those assumptions, you
>> could actually learn what the idea is behind it.
> 
> Oh, so now you're claiming that I don't know how VMware works?

Given that you don't seem to understand how linked clones work or how 
they are, I'm suggesting that maybe you should read up on the idea rather 
than making wild assumptions about it.

> When you create a VM, it starts with one file for the disk image. Each
> time you take a snapshot, it stops writing to the current image file,
> and creates a new file which is a delta against the previous one. When
> you make a "full clone", it copies all the data. When you create a
> "linked clone", it creates a new VM, but it's base disk image is just a
> delta against the linked VM, just like a snapshot.

Correct.  And if you delete the base vmdk image, what would you expect to 
happen when using a linked clone?

> I don't know off the top of my head how Virtual Box does it.

And the VirtualBox documentation does in fact describe this.  But hey, at 
least you're saying "I don't know how it does this" rather than making an 
incorrect assumption based on no knowledge.  So that's progress. ;)

> I'm still not seeing why you would want to transfer a disk from one VM
> to another - except perhaps, as you say, for data transfer (if you can't
> get a more sane method to work).

I'm working with a product right now that actually does this in order to 
personalize the image.  The underlying virtualization technology is 
XenServer, and the developers opted to create a LiveCD ISO to boot the VM 
from that customizes the image (due to a lack of APIs in XenServer to do 
this).  They transfer the disk files to a temporary VM that mounts them 
after booting the LiveCD image.

One benefit is that this allows them to be hypervisor-agnostic - it's a 
technique that works with any hypervisor that can boot from an ISO.

Jim

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