[Qemu-devel] SIGTERM signal to qemu-kvm process

[Qemu-devel] SIGTERM signal to qemu-kvm process

[Jatin Davey]

[-- Attachment #1: Type: text/plain, Size: 357 bytes --]

Hi

I am using QEMU 0.12.1 as the hypervisor in my RHEL installation of 6.5.

I wanted to know if there are any side-effects with respect to VM image 
corruption when i use SIGTERM signal to kill a qemu-kvm process which 
effectively stops my VM running on the host.

Appreciate if you can provide me some valuable information in this regard.

Thanks
Jatin

[-- Attachment #2: Type: text/html, Size: 677 bytes --]

Re: [Qemu-devel] SIGTERM signal to qemu-kvm process

[Kevin Wolf]

Am 08.04.2015 um 07:07 hat Jatin Davey geschrieben:
> I am using QEMU 0.12.1 as the hypervisor in my RHEL installation of 6.5.
> 
> I wanted to know if there are any side-effects with respect to VM image
> corruption when i use SIGTERM signal to kill a qemu-kvm process which
> effectively stops my VM running on the host.
> 
> Appreciate if you can provide me some valuable information in this regard.

Sending SIGTERM is equivalent to sending a 'quit' monitor command. This
is a clean shutdown as far as qemu is concerned, but of course it isn't
for your guest OS.

If your guest behaves correctly, you may lose data that wasn't flushed
to disk yet, but you should not get any corruption. The image file
structure itself (i.e. what 'qemu-img check' checks) should be fully
consistent.

Sending SIGKILL is a bit worse (just like a host crash/power failure),
because then even the image file may be inconsistent. But again, if the
guest behaves correct (and assuming there are no qemu bugs and you're
not using cache=unsafe), even in this case the result should never be
corruption, but only loss of data that wasn't flushed to disk yet.

Kevin

Re: [Qemu-devel] SIGTERM signal to qemu-kvm process

[Jatin Davey]

On 4/8/2015 9:06 PM, Kevin Wolf wrote:
> Am 08.04.2015 um 07:07 hat Jatin Davey geschrieben:
>> I am using QEMU 0.12.1 as the hypervisor in my RHEL installation of 6.5.
>>
>> I wanted to know if there are any side-effects with respect to VM image
>> corruption when i use SIGTERM signal to kill a qemu-kvm process which
>> effectively stops my VM running on the host.
>>
>> Appreciate if you can provide me some valuable information in this regard.
> Sending SIGTERM is equivalent to sending a 'quit' monitor command. This
> is a clean shutdown as far as qemu is concerned, but of course it isn't
> for your guest OS.
>
> If your guest behaves correctly, you may lose data that wasn't flushed
> to disk yet, but you should not get any corruption. The image file
> structure itself (i.e. what 'qemu-img check' checks) should be fully
> consistent.
>
> Sending SIGKILL is a bit worse (just like a host crash/power failure),
> because then even the image file may be inconsistent. But again, if the
> guest behaves correct (and assuming there are no qemu bugs and you're
> not using cache=unsafe), even in this case the result should never be
> corruption, but only loss of data that wasn't flushed to disk yet.
>
> Kevin
Thanks Kevin.

Appreciate your prompt response in this regard.

Thanks
Jatin