[systemd-devel] Enabling timesyncd in virtual machines

Kay Sievers kay at vrfy.org
Sun Mar 15 12:03:24 PDT 2015

On Sun, Mar 15, 2015 at 7:50 PM, Zbigniew Jędrzejewski-Szmek
<zbyszek at in.waw.pl> wrote:
> On Sun, Mar 15, 2015 at 07:47:46PM +0100, Kay Sievers wrote:
>> On Fri, Mar 13, 2015 at 8:25 PM, Michael Marineau
>> <michael.marineau at coreos.com> wrote:
>> > Greetings,
>> >
>> > Currently systemd-timesyncd.service includes
>> > ConditionVirtualization=no, disabling it in both containers and
>> > virtual machines. Each VM platform tends to deal with or ignore the
>> > time problem in their own special ways, KVM/QEMU has the kernel time
>> > source kvm-clock, Xen has had different schemes over the years, VMware
>> > expects a userspace daemon sync the clock, and other platforms are
>> > content to drift with the wind as far as I can tell.
>> >
>> > I don't know of a robust way to know if a platform needs a little
>> > extra help from userspace to keep the clock sane or not but it seems
>> > generally safer to try than to risk drifting. Does anyone know of a
>> > reason to leave timesyncd off by default? Otherwise switching to
>> > ConditionVirtualization=!container should be reasonable.
>> Sounds reasonable. Until someone has a better or clear idea how to
>> solve that reliably, I turned the option around.
> What about adding
> ConditionVirtualization=!kvm ?

Even there, things like leap seconds are not covered. And I'm not sure
if the "paravirtualized clock" is always configured. I guess it's
safest bet to just keep timesyncd running, until someone knows for
sure when we can optimize it away for which environment.


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