CentOS virt - Feb 2014 - Problem with lvm disks assigned to kvm guests

Hi all,

 I have a strange problem when I use lvm disks to expose to virtual
guests (host is CentOS 6.5 x86_64). If I remove a kvm guest and all
lvm disks attached to it, and I create a new kvm with another lvm
disks that use the same disk space previously assigned to the previous
kvm guest, this new guest sees all partitions and data. Creating new
lvm volumes with different names to this new kvm doesn't resolves the
problem.

Any idea why??

Thanks.

On 06.02.2014 11:45, C. L. Martinez wrote:
> Hi all,
>
>   I have a strange problem when I use lvm disks to expose to virtual
> guests (host is CentOS 6.5 x86_64). If I remove a kvm guest and all
> lvm disks attached to it, and I create a new kvm with another lvm
> disks that use the same disk space previously assigned to the previous
> kvm guest, this new guest sees all partitions and data. Creating new
> lvm volumes with different names to this new kvm doesn't resolves the
> problem.
>
> Any idea why??
When you delete a volume the data isn't cleared only the metadata 
removed so if you later create a new volume that ends up using the same 
area on disk then you will see the old data as expected.
If you don't want this to happen then you need to overwrite the volume 
before you delete it.

This is a general issue in virtualization/clouds that you need to take 
into account for security reasons. See for example:
https://github.com/fog/fog/issues/2525

Regards,
   Dennis