Re: SIGTERM to qemu-kvm process destroys qcow2 image?

[Avi Kivity <avi@redhat.com>]

On 12/17/2009 02:52 AM, Kenni Lund wrote:
> Hi
>
> Sorry if this is a stupid question, but is it expected behaviour that
> a qcow2 image will/can get damaged by killing the qemu-kvm process
> with a SIGTERM signal?
>
>    

If it does, that's a serious bug.  qcow2 should survive SIGTERM, 
SIGKILL, and host power loss.

> I would expect data on filesystems within the virtual machine to
> potentially get damaged if it's in use, but I though that the qemu-kvm
> process would take care of finishing its writes correctly to the qcow2
> image before shutting down, ensuring the integrity of the qcow2 image.
>    

No, it uses O_SYNC writes to ensure all writes are completed, and orders 
writes carefully so the image is consistent at all times.

> Yesterday I entered an invalid boot device as an argument to my
> qemu-kvm command for my Windows XP machine, causing an error about a
> missing boot device in the qemu BIOS/POST. As I didn't have any
> filesystems mounted inside the virtual machine (since it was stuck at
> the BIOS asking for a device to boot), I did a kill $pid, fixed the
> boot device in the qemu-kvm command and tried booting again...but with
> no luck, whatever I try now with qemu-kvm gives me the error:
> qemu: could not open disk image /data/virtualization/WindowsXP.img
>
> And qemu-img (check, convert, etc) gives me:
> qemu-img: Could not open 'WindowsXP.img'
>    

Can you post the first 4K of the image?  It shouldn't contain private 
data, but go over it (or don't post) if you sensitive information there.

> Is this expected behaviour? Luckily I do have backups of the most
> important data on this machine, I'm just happy this didn't happen to
> any of my critical machines :-/
>
>    


It is not.

> I'm on qemu-kvm 0.11.0 with kernel modules from 2.6.31.6.
>    

Should be recent enough.

-- 
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signature is too narrow to contain.