[ntp:questions] Re: ntpd, boot time, and hot plugging

Tom Smith smith at cag.lkg.hp.com
Fri Feb 4 18:59:39 UTC 2005


Brad Knowles wrote:
> At 4:21 AM +0000 2005-02-04, Tom Smith wrote:
> 
>>  # time ntpd -gq [13 servers in ntp.conf]
>>  ntpd: time slew -0.000373s
>>
>>  real    1m43.03s
>>  user    0m0.10s
>>  sys     0m0.60s
> 
> 
>     Yes, but what does that ntp.conf look like?  Are you using iburst?  
> Any authentication?  Manually setting minpoll and/or maxpoll?  Did you 
> have a good drift file to start with?
> 
>     You need to provide some more specifics before you can make an 
> attempt to compare this to ntpdate.
> 
>>  # time ntpdate -b [three selected servers]
>>   3 Feb 22:44:45 ntpdate[186032]: step time server [IP address] offset 
>> -0.000157 sec
> 
> 
>     Not comparable.  You need to include all thirteen servers before 
> this could potentially be considered comparable.
> 

As you wish...

# cat /etc/ntp.drift
-2.653

# ntpq -p
      remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
  LOCAL(1)        LOCAL(1)         5 l   41   64  377    0.000    0.000   0.004
  [IP.255]        0.0.0.0         16 u    -   64    0    0.000    0.000 4000.00
-[name]          .TRUE.           1 u  468 1024  377   12.741   -0.950   0.092
-[name]          .WWVB.           1 u  470 1024  377    1.388    1.015   1.216
-[name]          [name]           2 u  135  256  337    0.004   -0.490   0.440
-[name]          .GPS.            1 u  997 1024  377   88.936    0.153   1.854
+[name]          .GPS.            1 u  603 1024  377   88.146    0.546   0.119
*[name]          .GPS.            1 u  764 1024  377   88.311    0.605   1.387
-[name]          .GPS.            1 u  783 1024  377   73.649    0.766  12.499
#[name]          [name]           2 u  652 1024  377   83.509   -0.371   0.725
-[name]          .GPS.            1 u  720 1024  377   32.581    1.203   0.082
+[name]          .GPS.            1 u  744 1024  377  105.719    0.604   1.952
-[name]          .GPS.            1 u  686 1024  377   92.301    3.050   0.447
#[name]          [name]           2 u  339 1024  176    0.796   -1.401   0.245
#[name]          [name]           2 u  520 1024  376   10.376   -2.257   0.814
  [name]          0.0.0.0         16 u    - 1024    0    0.000    0.000 4000.00

# time ntpd -gq [above 14 servers/peers with iburst, plus local. No authentication.
                  Default min/max poll. All appropriate for long-term time
                  maintenance.]
ntpd: time slew 0.000527s

real    0m45.00s
user    0m0.11s
sys     0m0.55s

[Note that ntpd -gq isn't really done when it unblocks. It has only
  initiated a slew. But we'll let that pass becasuse the time is
  already way more than "good enough".]

# ntpdate -b [same set of servers and peers, except no local clock. Way
               overconfigured for one-time "good enough" acquisition at boot.]
  4 Feb 13:21:32 ntpdate[201766]: step time server [IP] offset 0.000647 sec

real    0m6.73s
user    0m0.00s
sys     0m0.00s

________________________________________________________________________
Tom Smith                       smith at alum.mit.edu,smith at cag.lkg.hp.com
Hewlett-Packard Company                          Tel: +1 (603) 884-6329
110 Spit Brook Road ZKO1-3/H42                   FAX: +1 (603) 884-6484
Nashua, New Hampshire 03062-2698, USA           Mobile: +1 978 397 3411



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