[pkg-ntp-maintainers] Bug#559634: Bug#559634: no kernel sync and "ntpdc -c kerninfo" reports incorrect estimates of time on Xen dom0

[Kurt Roeckx]

On Sat, Dec 05, 2009 at 05:12:13PM -0500, Michael Bilow wrote:
> Package: ntp
> Version: 1:4.2.4p4+dfsg-8lenny2
> Severity: normal
>
> 
> 
> 
> This is taking place on Xen dom0, not domU. (The name of the server --
> the Xen host -- is "virtual1".) As far as I understand, ntp should work
> normally on dom0.

I don't know much about xen, but I think that's what I understood
too.

What I see in your bug report is:
- It's synching to navobs1.gatech.edu
- It has an offset of about 35 ms to the system peer
- It claims to run at stratum 2
- The kernel reports back abnormal values, like 0 pll offset
  and 16 s for est and max error and that it's unsynced,
  and a suspiciously low pll frequency.

I'm guessing that you see alot of "time reset" messages in
/var/log/daemon.log and that if you look at the output
of ntpq -p you see the offset slowly go up until just
after such a time reset message?

How long is ntpd running?  Does the "pll frequency" change?
(It should change very slowly over time).

Note that the first time ntp is started it needs to adjust
the frequency.  This process ussually takes about 24 hours
to find the right frequency.  It works best if there is
no ntp.drift file when ntp is started, else it's assuming
the value is about right and will take alot longer.  This
also means a reboot after ntp was run for the first time
but didn't get the frequency yet will have a negative impact.


Kurt