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Old 11-30-2009, 03:34 PM
Jonathan Garden
 
Default timekeeping on VM - ntpd running

This is really stupid question. But referring to: http://lists.centos.org/pipermail/centos/2009-October/083791.html
I don't see any line related to ntpd in my /var/log/messages . Do I need to turn-on ntpd for timekeeping on VMs? Some people say not to use ntpd on VMs for timekeeping or is it ntpdate cron job? Can someone please elaborate on this?


Thanks,
Jonathan.

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Old 11-30-2009, 03:46 PM
Brian Mathis
 
Default timekeeping on VM - ntpd running

On Mon, Nov 30, 2009 at 11:34 AM, Jonathan Garden <jgarden21@gmail.com> wrote:
> This is really stupid question. But referring to:
> http://lists.centos.org/pipermail/centos/2009-October/083791.html
> I don't see any line related to ntpd in my /var/log/messages . Do I need to
> turn-on ntpd for timekeeping on VMs? Some people say not to use ntpd on VMs
> for timekeeping or is it ntpdate cron job? Can someone please elaborate on
> this?
>
> Thanks,
> Jonathan.
>

Did you read through the VMware KB that is linked to twice in that
link you posted? That reviews all of the current best practices from
VMware. "Some people" tend to repeat things they read on the Internet
somewhere, so it's best to always check with the authoritative source
(VMware in this case). You almost certainly don't want to be using
ntpdate.
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Old 11-30-2009, 04:14 PM
Thomas Harold
 
Default timekeeping on VM - ntpd running

On 11/30/2009 11:34 AM, Jonathan Garden wrote:
> This is really stupid question. But referring to:
> http://lists.centos.org/pipermail/centos/2009-October/083791.html
> I don't see any line related to ntpd in my /var/log/messages . Do I need
> to turn-on ntpd for timekeeping on VMs? Some people say not to use ntpd
> on VMs for timekeeping or is it ntpdate cron job? Can someone please
> elaborate on this?
>

On Xen guests, unless /proc/sys/xen/independent_wallclock is set to 1,
the DomU will slave itself to the Dom0 clock. So you probably don't
need NTP inside the DomU. Our Dom0 uses ntpd to keep itself
synchronized with the internal time servers on our LAN.

Whether that is better then using ntpd combined with setting that flag
to zero... I'm not sure.
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Old 11-30-2009, 06:08 PM
Brian Mathis
 
Default timekeeping on VM - ntpd running

On Mon, Nov 30, 2009 at 12:14 PM, Thomas Harold <thomas-lists@nybeta.com> wrote:
> On 11/30/2009 11:34 AM, Jonathan Garden wrote:
>> This is really stupid question. But referring to:
>> http://lists.centos.org/pipermail/centos/2009-October/083791.html
>> I don't see any line related to ntpd in my /var/log/messages . Do I need
>> to turn-on ntpd for timekeeping on VMs? Some people say not to use ntpd
>> on VMs for timekeeping or is it ntpdate cron job? Can someone please
>> elaborate on this?
>
> On Xen guests, unless /proc/sys/xen/independent_wallclock is set to 1,
> the DomU will slave itself to the Dom0 clock. *So you probably don't
> need NTP inside the DomU. *Our Dom0 uses ntpd to keep itself
> synchronized with the internal time servers on our LAN.
>
> Whether that is better then using ntpd combined with setting that flag
> to zero... I'm not sure.

The OP link is talking about VMware guests, not Xen. You can't apply
knowledge from one to the other.
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