Re: accessing unallocated VM disk areas

[Bacon Zombie <baconzombie () gmail com>]

Hey Robin,

First think I thought of when I read your email was the step I had to go
through to enable "raw" SATA access in ESXi.

http://cyborgworkshop.org/2011/01/08/enabling-raw-sata-access-in-esxi-free/

This could be handing for testing your theories since VMWare thinks it's
dealing with a Virtual HD but it writing to a real disk you can disconnect
and boot in another system like any other drive.

Hope this helps.


On 29 April 2013 11:09, Robin Wood <robin () digininja org> wrote:

> I had this random thought last night that I don't have time to test out so
> was wondering if anyone else knew the answer...
>
> When you create a disk in VirtualBox it lets you create it as a
> dynamically growing one so that the file on host disk starts small but
> grows as you write more data into it from the guest. If in the guest you
> try to read areas of the disk which have not yet been created, for example
> by using dd to clone the whole disk, what do you get from the areas which
> haven't yet been created?
>
> I'd guess it would be either nulls or random stuff but just wondering. I
> could lab it up but don't have time at the moment.
>
> What if you use direct disk write to write to the last sector? Does the
> whole disk then get created on the host or does it do some smart
> allocation? Or does it just crash?
>
> Does VMWare behave the same? Could checking this space be a way to try to
> identify if you are in a VM? I know there are other, better, ways but the
> more options you have the better.
>
> Robin
>
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-- 


BaconZombie

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