xen vm not keeping date/time properly

Ryan Golhar golharam at umdnj.edu
Fri Jan 23 15:05:53 UTC 2009

Jose R R wrote:
> 2009/1/22 Ryan Golhar <golharam at umdnj.edu>:
>> I've seen a ton of messages like this but no solution that works.  I have a
>> 64-bit RHEL 5 machine running multiple guests.  Dom0 keeps time using ntp
>> and works well.
>> I initially had the virtual machines do the same thing, but they failed to
>> keep time properly.  I've since disabled ntp on the guests and haven't found
>> a solution.
> Those organizations that offer Virtual Private Servers (VPS) would not
> be in business if they had not found a solution to the problem you
> describe ;)  As an instance, using such technologies as HyperVM (<
> http://lxlabs.com/software/hypervm/ >) they offer their clients *any*
> of a variety of Xen DomU GNU/Linux distributions.
> You may want to try the following procedure (from an CentOS list):
> ----------Begin fragment-------------------------------
> Put this in /etc/sysctl.conf :
> xen.independent_wallclock = 1
> and then execute sysctl.
> What happens then is that the domU will do it's own timekeeping and no
> longer follow the dom0. Now this also means that you need to run a
> ntpd inside the domU to make sure it's clock keeps syncronised.
> -----------End Fragment---------------------------------
> < http://lists.centos.org/pipermail/centos-virt/2008-January/000185.html >
> Best regards.

Yes, I've seen this.  There is not indication on whether this setting 
should be inside the guest or on the host.  MY guess was the guest.  I 
put this in, restart the guest and it had no effect.  I believe (from 
google searching) this only applies to paravirtualized machines.  Mine 
is fully virtualized.

Any other ideas? :)


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