[CentOS-virt] Problem with lvm disks assigned to kvm guests

Thu Feb 6 12:16:34 UTC 2014
Mark Milhollan <mlm at pixelgate.net>

On Thu, 6 Feb 2014, C. L. Martinez wrote:
>On Thu, Feb 6, 2014 at 11:01 AM, Dennis Jacobfeuerborn
><dennisml at conversis.de> wrote:
>> On 06.02.2014 11:45, C. L. Martinez wrote:

>>>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.

>>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.

>dd if=/dev/zero of=/dev/sdc1 bs=1M (it is a 1TiB disk), will erase all 
>data and partitions created by the kvm guest??

You wanted to deal with an LV, so the LV is what you should write, not 
the underlying disk as that would destroy whatever else is present -- 
possibly requiring that you recreate the PV and VG.  So, 

Or as also mentioned, you might clean the old lvol before you destroy 
it.  Again, of=/dev/mapper/vg-lv.