Re: [gentoo-user] NTP problem

[Brandon Enright <bmenrigh@ucsd.edu>]

On Wed, 2006-02-22 at 02:41 -0600, Anthony E. Caudel wrote:
> Brandon Enright wrote:
> > On Wed, 2006-02-22 at 01:32 -0600, Anthony E. Caudel wrote:
> > 
> >>My system was off about 10 days and when I turned it back on, I began
> >>getting these messages in my logwatch:
> >>
> >>"Time Reset
> >>   time stepped -0.133773
> >>   time stepped -0.662954
> >>   time stepped +0.271164
> >>   time stepped +0.461200
> >>   time stepped -0.787647
> >><snip>
> >>
> >> Time Reset 25 times (total: -1.239782 s  average: -0.049591 s)
> >>
> >> **Unmatched Entries**
> >> synchronized to 80.35.31.228, stratum 3
> >> synchronized to 80.35.31.228, stratum 4
> >><snip>
> >> synchronized to 80.35.31.228, stratum 4
> >> synchronized to 80.35.31.228, stratum 3
> >> Listening on interface wildcard, 0.0.0.0#123
> >> Listening on interface eth0, 192.168.1.100#123
> >> Listening on interface lo, 127.0.0.1#123
> >> kernel time sync status 0040"
> >>
> >>I rebooted thinking it needed to stabilize but it still gets them. I
> >>have ntp-client and ntpd both in the "default" runlevel.
> >>
> >>This seems like an awful high number of resets.  Much more than I used
> >>to get.
> >>
> >>Tony
> > 
> > 
> > 
> > Those are some pretty big jumps.  What does "ntpq -c peers" and "ntpq -c
> > rv" output?  Also, what are the first few lines (the restrict entries)
> > of your ntp.conf?
> > 
> > Brandon
> > 
> ntpq -c peers:
> 
>   remote         refid      st t when poll reach   delay   offset jitter
> ==============================================================================
> *ntp3.usv.ro     .PPS.      1 u   70 1024  377  203.080    7.338   1.485
> 
> ntpq -rv:
> 
> assID=0 status=06a4 leap_none, sync_ntp, 10 events, event_peer/strat_chg,
> version="ntpd 4.2.0a@1.1190-r Thu Dec  8 09:35:31 CST 2005 (1)"?,
> processor="i686", system="Linux/2.6.15-gentoo-r1", leap=00, stratum=2,
> precision=-20, rootdelay=203.080, rootdispersion=34.319, peer=35268,
> refid=80.96.120.249,
> reftime=c7a69e5a.a3227d02  Wed, Feb 22 2006  2:24:58.637, poll=10,
> clock=0xc7a6a0b6.78a5bd94, state=4, offset=7.338, frequency=35.514,
> noise=2.162, jitter=0.891, stability=64.582
> 
> ntp.conf:
> 
> restrict default nomodify nopeer
> restrict 127.0.0.1
> 
> Tony


So from your output a couple issues stick out.  You're only peering with
one machine which generally doesn't work so well.  You're probably
better off just using ntpdate periodically if you are only going to
sample one server.

Also, the delay on the server you are polling is over 200 ms.  I'm not
sure where ntp3.usv.ro is located but it is over 260ms for me too.  With
this high network delay, slight network jitter can make your clock think
it is way off.  Your machine thinks it is 7.3 ms off.  If you had more
servers to peer with and *much* lower average delay between those
servers your clock would stabilize.  As it stands now, you clock
probably won't ever stabilize because your network is the primary source
of uncertainty.

For comparison, here is my ntpq -c rv output:

assID=0 status=06f4 leap_none, sync_ntp, 15 events,
event_peer/strat_chg,
version="ntpd 4.2.0a@1.1190-r Mon Oct 17 21:31:52 PDT 2005 (1)"?,
processor="i686", system="Linux/2.6.10-gentoo-r6", leap=00, stratum=2,
precision=-20, rootdelay=21.642, rootdispersion=41.662, peer=12542,
refid=132.249.20.88,
reftime=c7a70d4a.975935fc  Wed, Feb 22 2006 16:18:18.591, poll=10,
clock=0xc7a70dc0.a5847f56, state=4, offset=-0.007, frequency=-31.438,
noise=1.052, jitter=2.529, stability=3.132

Notice my offset is pretty marginal and rootdelay is rather low.  If you
can get your root delay down you should see your offset and stability
improve.

Brandon

-- 
Brandon Enright
UCSD ACS/Network Operations
bmenrigh@ucsd.edu

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