[ntp:questions] Re: New to NTPD
Richard B. Gilbert
rgilbert88 at comcast.net
Tue May 9 16:48:38 UTC 2006
Ted Gervais wrote:
> Well I finally am moving away from netdate and have ntpd installed and
> I brought it up using ntpd -g, and hope that is ok.
> Also I have no idea that it is doing anthing? How do I know that it is
> The drift file has only one entry in it, and that is all zeros..
> Is there some way that I can watch what is happening like the way I watch
> log files using 'tail -f messages' ??
> I have all the logfile stuff turned on so I can read any and all stuff that
> is happening and yet while that says a few things I at this point don't
> know that it is doing anything with the system time.
> I am running linux (slackware 10.2)..
It will show you a "billboard" listing, for each server:
1. whether it is selected (*=selected, +=candidate, -not a candidate, X
2. the name or IP address
3. the reference ID
4. the stratum
5. the type
6. when it was last polled
7. the poll interval
8. reachability (eight bit shift register in octal. A 1 is shifted in
from the right for each response from the server and a 0 for each
failure to respond; 0 is bad 377 is good.
9. The round trip delay to and from that server, in milliseconds.
10. The offset of your clock from that server, in milliseconds
11. The jitter, a measure of the random noise in the time received; low
numbers are good.
This display can look quite disappointing when you cold start ntpd.
Ntpd may need several hours to get your clock into really good
Here's a sample:
sunblok_$ ntpq -p
remote refid st t when poll reach delay offset
*GPS_ONCORE(0) .GPS. 0 l 4 16 377 0.000 0.003
sunburn .WWV. 1 u 165 1024 377 0.450 42.953
+Internet-A .PSC. 1 u 42 64 377 17.061 1.635
-Internet-B .CDMA. 1 u 41 64 377 19.267 4.958
+Internet-C 126.96.36.199 2 u 12 64 377 16.014 2.134
+Internet-D 188.8.131.52 2 u 1 64 377 12.711 1.992
LOCAL(0) LOCAL(0) 10 l 35 64 377 0.000 0.000
This server uses a Motorola Oncore GPS Timing receiver as a reference
clock. It is selected as the primary synchroniztion source. Sunburn is
a server on my LAN using a WWV receiver as reference clock; it's the
middle of the day here and both signal reception and performance are
extremely poor. Internet-A, Internet-C and Internet-D are part of the
"selection" set and act as an "advisory committee". Internet-B with the
longest round trip delay and a relatively high value of jitter is not
being used for anything at this time.
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