[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 
> running.
> 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 
> running.
> 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)..
> 
> 
> 

ntpq -p

It will show you a "billboard" listing, for each server:
1. whether it is selected  (*=selected, +=candidate, -not a candidate, X 
   insane.
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 
synchroniation.

Here's a sample:

sunblok_$ ntpq -p
      remote           refid      st t when poll reach   delay   offset 
  jitter
==============================================================================
*GPS_ONCORE(0)   .GPS.            0 l    4   16  377    0.000    0.003 
  0.001
  sunburn         .WWV.            1 u  165 1024  377    0.450   42.953 
   1.821
+Internet-A      .PSC.            1 u   42   64  377   17.061    1.635 
  2.089
-Internet-B      .CDMA.           1 u   41   64  377   19.267    4.958 
  1.368
+Internet-C      18.145.0.30      2 u   12   64  377   16.014    2.134 
  3.440
+Internet-D      128.59.39.48     2 u    1   64  377   12.711    1.992 
  2.621
  LOCAL(0)        LOCAL(0)        10 l   35   64  377    0.000    0.000 
   0.001

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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