[CentOS] timekeeping on VMware guests

Dag Wieers dag at wieers.com
Wed Oct 14 01:31:07 UTC 2009


On Tue, 13 Oct 2009, Ray Van Dolson wrote:

> On Tue, Oct 13, 2009 at 04:31:03PM -0700, nate wrote:
>> Carlos Santana wrote:
>>> Howdy,
>>>
>>> I am having time-drift issues on my CentOS VM. I had referred to
>>> following documentation:
>>> http://wiki.centos.org/TipsAndTricks/VMWare_Server , however it didn't
>>> help. I used kickstart for creating this VM and I am listing important
>>> steps in ref to timekeeping issue. Any comments or suggestion would be
>>> appreciated.
>>
>> [..]
>>> VMware Tools not installed.
>>
>> You should certainly install vmware tools, and enable time sync to
>> the guest. Also don't run an ntp server in a Vmware VM.
>
> This is what I'd always thought, but the VMware KB link[1] referenced
> in the other reply in this thread seems to indicate that best practice
> is to use NTP + kernel w/ clock/divider options (unless it's new enough
> to not need it) and to *not* use the VMware Tools host time sync.
>
> That said, you should certainly still have VMware Tools installed, it
> just sounds like the host time sync is no longer preferred...
>
> Also note that they recommend you remove the local time source in
> ntp.conf...

Indeed, they changed course over time once they learned that NTP could be 
made to work reliably when using tinker panic 0. I have had my share of 
VMware timekeeping troubles the past 5 years, mostly because the 
recommendations didn't always apply to what we were seeing.

We still use Host-Guest synchronization for ESX 2.0 VM guests, but most of 
the infrastructure has been migrated, recently to ESX 3.5. VMware never 
could confirm that the recommendations laid out in the knowledge base 
article also applies to ESX 2.0.

They seem to update that document (and the timekeeping PDF) for every new 
ESX release, and removing anything that applied to the previous release 
:-/ And without a detailed  changelog and no access to previous versions 
of the document you may get paranoid or get into discussions based on 
different copies of that document.

I've been there too :-)

-- 
--   dag wieers,  dag at wieers.com,  http://dag.wieers.com/   --
[Any errors in spelling, tact or fact are transmission errors]


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