[CentOS] NTP and virtual guests

[James B. Byrne]

On Mon, May 28, 2012 10:10, Bob Hoffman wrote:
> On 5/28/2012 9:59 AM, James B. Byrne wrote:
>> On Mon, May 28, 2012 08:50, Reindl Harald wrote:
>>>
>>> Am 28.05.2012 14:41, schrieb James B. Byrne:
>>>> when power returned all of the restored guests were immediately
>>>> shutdown by ntp because the time differential between the
>>>> restored systems and that of the ntpd sync servers exceeded
>>>> the panic threshold.
>>> how can ntpd shutdown a guest?
>> I have no idea.  Perhaps I misunderstood what the ntpd man page
>> referred to as a panic.
>>
>> If it is not ntpd then I still need to discover some way of ensuring
>> that all the KVM guests that were active at the time of a power
>> failure automatically come back on line when the KVM host system
>> starts up.  I cannot find any reference to how this is done.
>>
>> Are there any recommended solutions?  These systems are on UPS
>> already
>> but the power failure duration exceeded the endurance of the the
>> UPS.
>>
> I know when ntp changes the time drastically (like ntpdate) my vsftpd
> just commits suicide and dies..
> I imagine something like that is going on with the lvm software either
> on the host or the kvm?
>
> I would suggest turning off ntp before long time shut downs...and
> (ugh) manually going through the host and all vms upon turn on and
> ntpdate them, then turn ntp on, then reboot to make it all come
> back on?
>
> perhaps a script that turns off ntp, runs ntpdate on host, then on
> each kvm upon reboot? this sounds rather scary.
>
>

I cannot find anything in the logs that explain what is happening to
me.  The evidence I have indicates that when the host kvm system is
powered off and restarted then the guests do not restart.  This
behaviour is at variance with a controlled shutdown wherein active
guests are (usually) restarted when the host reboots. I infer from
this observation that system scripts already handle this more or less
correctly.

I suppose that I could just create an init script that read a custom
status file and restated every domain that it found therein using
virsh.  However, if such a beast already exists then I would rather
not have to reinvent the wheel.

Is anyone aware of such a script or where one might be found?  I am
not havig much luck with Google this morning.


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