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Re: [Xen-users] NTP service in DomU

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: Tony Hoyle <tmh@xxxxxxxxxxxx>
  • Date: Wed, 04 Jul 2007 10:30:09 +0100
  • Delivery-date: Wed, 04 Jul 2007 02:28:08 -0700
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  • List-id: Xen user discussion <xen-users.lists.xensource.com>

Jordi Espasa Clofent wrote:
¿It is not possible to build a NTP service in domU which would be independent from dom0? According to my own tests, it seems not.

Set independent_wallclock.

If this issue is true I think it's a big limitation for XEN.
¿what happens if you require to set up your domU with diferent NTP services (as clients)?

Why though? There's only one time to sync to to, and time sync within virtual machines is never going to be quite as accurate as bare hardware.. if you need millisecond accuracies then forget virtual machines (and use a realtime OS).

I can't think of a scenario where it would be a requirement to sync each domu off a different time source than the dom0 (even if you're using them independently the closest and therefore most accurate time source to sync to is in fact the dom0). Xen does allow this, it's just a bit pointless.

Rarely the time on the domu seems to get screwed up (had one that was about 4 hours out), but I've only seen that happen a couple of times and a reboot of the domu fixed it.


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