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

[Jérôme]

Le Thu, 24 Sep 2015 05:32:45 +0800,
Bill Kenworthy <billk at iinet.net.au> a écrit :

> 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.

My use case is when rebooting the host (after a kernel update, for
instance). The gap is about 2 minutes.
 
> 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.

The guest-set-time command from the host works as well (but requires
guest agent). I just don't know how to launch it automatically on guest
resume.

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

Interesting answer.

I figured that while interrupting the host for a few minutes,
suspending the guest could be a nicer option. I may be wrong.

Anyway, the host shall not be rebooted that often, and I think if I
don't find any satisfying answer, I may choose guest shutdown instead
of suspend.

In practice, my guests will likely have the same OS version, therefore
the same updates and the same reboot needs. There's no point suspending
a guest when rebooting the host if the guest must be rebooted anyway.

-- 
Jérôme