[libvirt-users] Time syncing after VM suspend/resume

[Bill Kenworthy]

Look into the "panic" option to ntpd - once the gap gets to big (such as
when the VM is suspended for a few hours) it goes into freewheel and
doesn't sync - its in the ntp docs.

ntpd doesn't work well (you get ages where a machine is way out of date,
or fails to sync ever.  I run either chrony (same problem) or ntpd and
run a script on startup to restart guest ntp/chrony from the host via ssh.

I don't think serious users suspend vm's much or this would have been
fixed long ago.

BillK


On 23/09/15 23:44, Jérôme wrote:
> Hi.
> 
> Thanks for answering.
> 
> Le 2015-09-23 17:34, Dominique Ramaekers a écrit :
> 
>> Linux has two methods to use ntp:
>>
>> ntpdate:
>> It will run once at boot time to sync time. (This is probably
>> installed on your system)
>> It will not run after suspend and resume... => no correction
> 
> Nope. This is not installed on my system.
>  
>> ntpd:
>> Continuously adjusts time. The deamon also calculates the drift to
>> anticipate differences.
>> I use this one and works perfectly.
> 
> This is installed (package ntp, Debian Jessie) and runs (I see
> /usr/sbin/ntpd in `ps aux`). But after more than 24h, the 2'17 gap
> between hwclock and date has not reduced a bit.
> 
> I guess this is not the place for me to debug my ntp issues, apart maybe
> from what could be related to the virtualization itself.
> 
> I understood from my readings (can't remember where precisely) that the
> fact that ntp wouldn't work was "normal", but if it is not, maybe trying
> to have it working is the way to go, rather than searching for a way to
> automatize guest-set-time.
>