Clock delays in FreeBSD guest VM on VirtualBox

Tim Judd tajudd at
Mon Sep 7 02:12:46 UTC 2009

On 9/6/09, Hashimoto <hsmtkk at> wrote:
> Hello.
> I am running several FreeBSD(8.0-BETA3) guest VMs
> on VirtualBox on OpenSolaris.
> On all hosts, I am configuring & running ntpd.
> However, only one host (naming HostX) can sync the clock.
> All hosts except for HostX cannot sync the clock.
> (The time delays about 10 minutes in an hour.)
> What's the cause of this problem?
> Regards.
> /etc/rc.conf
> ntpd_enable="YES"
> ntpd_sync_on_start="YES"
> /etc/ntp.conf (default config file)
> server iburst maxpoll 9
> server iburst maxpoll 9
> server iburst maxpoll 9
> --
> Kouki Hashimoto
> hsmtkk at

Timing problems can be due to kern.hz

The older kern.hz was set to 100, and now it's set at 1000

The hardware clock may need adjusting, see   sysctl kern.timecounter.choice

Only one that seems relatively current is installing the vmtools with
vmware hypervisor.  Said tools even support guest shutdown and the

I would say without tools support, you have slim possible chances to
synchronize timings, and timing problems will keep you guessing.

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