[ovirt-users] Time synchronization in guest OS for Hosted Engine VM (for Kerberos)

Robert Story rstory at tislabs.com
Wed Sep 28 12:10:19 UTC 2016

On Tue, 27 Sep 2016 13:22:29 -0400 (EDT) Michal wrote:
MS> > On 27 Sep 2016, at 19:12, aleksey.maksimov at it-kb.ru wrote:
MS> > 
MS> > I'm afraid that in the future OS time may get out of sync because of kvm-clock
MS> > And as a result Kerberos may stop working
MS> > I hope I explained clearly  
MS> Sorry, not really. You said you set up ntpd/chrony correctly. So how can the time get out of sync? Why do you think it can be because of kvmclock anyway? Do you refer to some specific bug?

I'd guess that it's a misunderstanding of what kvmclock is. Someone
guessing based on the name might think that it keeps the vm time in sync
with the host. Which might lead one to think it would conflict with ntp
(two different things trying to manage time).

If you know that kvmclock is essentially just a way to monitor the passage
of time (tick-tock-tick-tock) using the host's timer, then it makes sense
that you need also need ntp to tweak the current time to adjust for the
minor drift inherit in any clock.


Senior Software Engineer @ Parsons
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