[Dovecot] "Time just moved backwards" in Dovecot in a Xen DomU

[Thierry DOSTES]

Hi,

Here comes an extract from Debian Wiki about Xen to allow a domU to keep 
its own time :

----
(...) your domU is likely using the xen clocksource instead of its own 
clock ticks. In practice, this seems to be the cause of infrequent 
lockups under load (and/or problems with suspending). A workaround is to 
decouple the clock in the domU from the dom0:

In your dom0 and domU /etc/sysctl.conf add the line: 
xen.independent_wallclock=1. On the dom0, edit the configuration file of 
the domU (e.g. /etc/xen/foobar.cfg and add (or expand) the extra-line: 
extra="clocksource=jiffies".

These settings can be activated without rebooting the domU. After 
editing the configuration files, issue sysctl -p and 
echo "jiffies"> /sys/devices/system/clocksource/clocksource0/current_clocksource 
on the domU prompt.

Because the clock won't be relying on the dom0 clock anymore, you 
probably need to use ntp on the domU to synchronize it properly to the 
world.
----

Hope this helps.

Thierry.


PGNet Dev a écrit :
> hi,
>
> On Mon, Oct 5, 2009 at 4:02 PM, Timo Sirainen <tss at iki.fi> wrote:
>   
>> And no ntpd in your DomU?
>>     
>
> nope.
>
>  service ntp status
>   Checking for network time protocol daemon (NTPD):   unused
>
>   
>>> any suggestions as to what/how to fix?
>>>       
>> If no one here can give you a good answer, I'd try some Xen mailing
>> list. I'm sure a lot of people are running Dovecot in Xen without time
>> problems. If you do find out the problem, please let us know also.
>>     
>
> i've been poring over the lists ... found nothing yet :-/
>