[openstack-dev] [nova][libvirt] - 'nova reboot' causes console-log truncated

Tony Breeds tony at bakeyournoodle.com
Tue Dec 23 01:04:58 UTC 2014

On Mon, Dec 22, 2014 at 04:36:02PM -0800, Surojit Pathak wrote:

> Hi Daniel,
> Having GA to do graceful restart is nice option. But if it were to just
> preserve the same console file, even 'virsh reboot' achieves the purpose. As
> I explained in my original analysis, Nova seems to have not taken the path,
> as it does not want to have a false positive, where the GA does not respond
> or 'virDomain.reboot' fails later and the domain is not really restarted. [
> CC-ed vish, author of nova
> <http://tripsgrips.corp.gq1.yahoo.com:8080/source/xref/nova/nova/>/virt <http://tripsgrips.corp.gq1.yahoo.com:8080/source/xref/nova/nova/virt/>/libvirt <http://tripsgrips.corp.gq1.yahoo.com:8080/source/xref/nova/nova/virt/libvirt/>/driver.py <http://tripsgrips.corp.gq1.yahoo.com:8080/source/xref/nova/nova/virt/libvirt/driver.py>
> ]
> IMHO, QEMU should preserve the console-log file for a given domain, if it
> exists, by not opening with O_TRUNC option, instead opening with O_APPEND. I
> would like to draw a comparison of a real computer to which we might be
> connected over serial console, and the box gets powered down and up with
> external button press, and we do not lose the console history, if connected.
> And that's what is the experience console-log intends to provide. If you
> think, this is agreeable, please let me know, I will send the patch to
> qemu-devel at .

The issue is more complex than just removing the O_TRUNC from the open() flags.

I havd a proposal that will (almost by accident) fix this in qemu by allowing
console log files to be "rotated".  I'm also waorking on a similar feature in

I think the tl;dr: is that this /shoudl/ be fixed in kilo with a 'modern' libvirt.

Yours Tony.
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