[Libvir] Restarting of libvirt_qemud daemon

Richard W.M. Jones rjones at redhat.com
Fri Mar 9 13:55:16 UTC 2007

Daniel P. Berrange wrote:
> On Fri, Mar 09, 2007 at 10:47:18AM +0000, Richard W.M. Jones wrote:
>> Daniel P. Berrange wrote:
>>> Thinking about later RPM upgrades I think we need to think about whether it
>>> will be possible to restart the libvirt_qemud while guests & networks are
>>> running. There's a couple of issues:
>>> - We do waitpid() to cleanup qemu & dnsmasq processes when we stop domains
>>>   & networks, or to detect when they crash. For the former, we could may
>>>   they daemons to avoid waitpid() cleanup, but we'd still need waitpid to
>>>   be able to detect shutdowns. There is also the issue of enumerating
>>>   running instances.
>> Maybe I'm missing something big here, but how would libvirt_qemud regain 
>> connections to the running qemu monitor ptys?
> That's one of the challenges to be addressed :-)  Fortunately the monitor
> is set to be exposed via /dev/pty/XXX, so if the restarted client can
> find out the path to the PTY, then it can re-open it. Maybe we just need
> to record a state file somewhere containing a PID & PTY path. 

Is it possible to start qemu with something like:

   qemu -monitor pipe:/var/some/known/place/pipe.UUID

and then just look in /var/some/known/place/ in order to find the 
running instances?


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