[libvirt-users] virsh attach makes qcow2 format disk to raw format

[李跃洲]

Hi Eric


Thanks for you answer, help me a lot


At 2013-12-13 06:25:44,"Eric Blake" <eblake at redhat.com> wrote:
>On 12/09/2013 09:03 PM, lyz_pro at 163.com wrote:
>> Hi all
>> 
>> I have a problem when I use `virsh attach` to attach a qcow2 disk to vm without argument --subdirver=qcow2
>> and this makes the qcow2 disk become a raw format disk, and the data in this disk is missing in guest os
>> and also I have used guestmout to confirm this, the same result.
>
>The format of a file is important.  By default, libvirt refuses to probe
>a file for its format, because any raw file can contain contents that
>look like any other format, making libvirt and/or qemu misbehave if the
>guest abused the raw contents to intentionally resemble a different
>format (this is a known CVE in the past).  You can flip an option in
>/etc/libvirt/qemu.conf to request libvirt to probe image formats, at
>which point you can then omit the format but the guest will still get
>the data from the qcow2 format instead of abusing the file as raw; but
>this is a security risk if you do not trust any guest that has ever run
>on the image file.
>
>> 
>> Is there any way to let me find back the data in this disk ?
>
>If the guest wrote to the disk, then I hope you had a good backup.  If
>the guest merely read from the disk but didn't write any data, then
>unplugging the disk and replugging with the correct qcow2 format will
>fix things.
>
>-- 
>Eric Blake   eblake redhat com    +1-919-301-3266
>Libvirt virtualization library http://libvirt.org
>
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