On Thu, Feb 6, 2014 at 11:17 AM, Dennis Jacobfeuerborn dennisml@conversis.de wrote:
On 06.02.2014 12:05, C. L. Martinez wrote:
On Thu, Feb 6, 2014 at 11:01 AM, Dennis Jacobfeuerborn dennisml@conversis.de wrote:
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
Many thanks Dennis ... Then if I do:
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??
That should work although if you want to be really safe you should probably use /dev/urandom instead of /dev/zero as using random data is a better way to deal with the problem of data remanence:
http://en.wikipedia.org/wiki/Data_remanence#Overwriting
Regards, Dennis
Ok, thanks ... This procedure can works when I reuse a full disk, but what about if I want to reuse only a logical volume??