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Re: [Xen-users] time synchronization problem (using NTP)

Ulrich Windl wrote:
On 11 Oct 2006 at 19:02, Christoph Purrucker wrote:

Hi Thomas,

As far as my experience shows, none of the ntp / independent_wallclock combinations work. We got the same problem here with xen 3.0.2 and kernel 2.6.16. It looks like ntpd can't set the time in DomUs with independent_wallclock set to 1 but the DomUs aren't using the exact time of Dom0 with independent_wallclock set to 0.
I'm running 2.6.16-2-xen-k7 with XEN 3.0 on both Dom0 and DomUs. A cron job on Dom0 runs "ntpdate ptbtime1.ptb.de" every night (shifting the time some milliseconds). All DomUs are perfectly in sync. /proc/sys/xen/independent_wallclock = 0 in all DomUs.


A plain "ntpd" also does the job once XEN's own synchronization (wich must be buggy) is disabled (sysctl -w xen.independent_wallclock=1):

Just a small update and a question.

Before setting wallclock=1 (mine was set to 0), the ntpd in my DomU was running about 2 minutes fast. There were entries in the ntpd.log file indicating that it was setting the clock back by 141 sec, but the "ntpq -p" output still showed an offset of 141 sec (-141000 msec).

Now it seems to be working properly (ntpd is now able to adjust the clock).

The ntp.conf file in the DomUs looks like:

server time1.example.com iburst
server time2.example.com iburst
server time3.example.com iburst
server time4.example.com iburst
server time5.example.com iburst
driftfile       /var/lib/ntp/ntp.drift
restrict default nomodify nopeer
restrict 127.0.0.1

(The timeN.example.com are our internal time servers. These are usually Dom0s. They currently access public servers but may eventually talk to a GPS clock directly.)

Still using Xen 3.0.2 here w/ the latest NTP version.

...

Will the sysctl command make that a permanent change? Or do I need to edit /etc/sysctl.conf and add that line at the end? (I'd guess that I need to add that in my DomUs.)



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