[ntp:questions] two machines syncing to the same master - hardware issues?

David Lord snews at lordynet.org
Fri May 31 14:22:18 UTC 2013


matthew.garman at gmail.com wrote:
> On Thursday, May 30, 2013 5:41:46 PM UTC-5, unruh wrote:
>>> My two machines are somewhat different: "oldbox" is running NTP 4.2.2 as ships with RedHat 5.7; "newbox" is running NTP 4.2.4 as ships with RedHat 6.3.
>> Why?
> 
> Because oldbox has a lot of other custom functions that haven't been validated against the newer OS.  newbox does only NTP, so we're not stuck with the older version.
> 
> 
>> Plots would be good. 
>> Plot the offset vs time from the peerstats file. You might discover that
>> your understanding is wrong. 
> 
> 
> Currently I'm not generating a peerstats file, but will change that after business hours this evening.
> 
>>> I'm measuring the offset via "ntpdate -q <peer ntp server>"
>> Very silly way of doing it, esp since your machine measures the offset
>> every few minutes already. 
> 
> Where can I access this information?  I assume from the peerstats file?  Or is there another mechanism for querying this pre-existing data?

There is a mass of documentation with most of ntpd
releases. Try <www.ntp.org>

There are some utilities with the distributions. I call
summary.sh from cron each night and that script gives
a summary of loopstats, peerstats and clockstats.


> 
>>> Is it possible there is a hardware problem with newbox?  I don't really understand NTP well enough to know where to start looking.
>> It is possible. What operating system is on newbox? And it could be that
>> something on the box is resetting the clock behind ntpd's back. 
> 
> newbox is running Redhat (CentOS actually) 6.3.
> 
> How can I determine if something else is messing with the clock?
> 
>> You can expect offsets of the order of 10-20microseconds IF the ntp
>> servers get their time from gps. If not, the servers themselves can be
>> woggling all over the place.
> 
> Is there any way to determine if the ntp servers are using GPS or not?
> 
> Thanks again.


$ ntpq -crv -p me6000g
associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync,
version="ntpd 4.2.6p5-o Wed Feb  1 07:49:06 UTC 2012 (import)",
processor="i386", system="NetBSD/6.1_STABLE", leap=00, stratum=2,
precision=-18, rootdelay=0.725, rootdisp=11.089, refid=192.168.59.61,
reftime=d55326e2.5822c70b  Fri, May 31 2013 13:40:50.344,
clock=d55328c1.b2d725b5  Fri, May 31 2013 13:48:49.698, peer=25540, tc=6,
mintc=3, offset=0.520, frequency=-49.924, sys_jitter=0.458,
clk_jitter=0.122, clk_wander=0.010, tai=35, leapsec=201207010000,
expire=201306280000
      remote       refid    st t when poll reach   delay   offset  jitter
========================================================================
+SHM(0)          .MSFa.     1 l   26   64  267    0.000   -0.652   1.176
-ns1.lordynet.or xxxxxxxxx  3 u   60   64  376    0.229    1.657   0.019
-ns3.lordynet.or xxxxxxxxx  3 u    2   64  377    0.354    1.683   0.058
-ns0.lordynet.or xxxxxxxxx  3 u   60   64  377    0.697    1.635   0.541
*me6000e.home.lo .PPSb.     1 u   21   64  377    0.725    0.520   0.457
-xxxxxxxxxxxxxxx xxxxxxxxx  2 u   13  256  377   18.766    2.822   0.159
-xxxxxxxxxxxxxxx xxxxxxxxx  2 u  101  256  377   20.567    2.689   0.347
+xxxxxxxxxxxxxxx xxxxxxxxx  2 u  135  256  377   26.693    2.044   0.290
-xxxxxxxxxxxxxxx xxxxxxxxx  2 u   76  256  377   27.286    2.523   0.247
-xxxxxxxxxxxxxxx xxxxxxxxx  2 u  257  256  377   42.265    3.263   0.243

$ ntpq -crv -p me6000e
associd=0 status=01fd leap_none, sync_pps, 15 events, kern,
version="ntpd 4.2.6p5-o Wed Feb  1 07:49:06 UTC 2012 (import)",
processor="i386", system="NetBSD/6.1_STABLE", leap=00, stratum=1,
precision=-18, rootdelay=0.000, rootdisp=1.655, refid=PPSb,
reftime=d55328c6.b349da0b  Fri, May 31 2013 13:48:54.700,
clock=d55328f6.f6f18593  Fri, May 31 2013 13:49:42.964, peer=54815, tc=6,
mintc=3, offset=-0.001, frequency=-35.098, sys_jitter=0.004,
clk_jitter=0.001, clk_wander=0.005, tai=35, leapsec=201207010000,
expire=201306280000
      remote       refid    st t when poll reach   delay   offset  jitter
========================================================================
*GPS_NMEA(2)     .GPSb.     4 l   50   64  377    0.000    7.655   8.881
oPPS(2)          .PPSb.     0 l   48   64  377    0.000   -0.001   0.004
+ns0.lordynet.or xxxxxxxxx  3 u   39   64  377    1.697    1.597   0.579
  ns2.lordynet.or 192.168.5  2 u   48   64  377    0.549   -0.339   0.518
+ns1.lordynet.or xxxxxxxxx  3 u   45   64  377    1.122    1.141   0.345
+ns3.lordynet.or xxxxxxxxx  3 u   29   64  377    0.750    1.467   0.477
+xxxxxxxxxxxxxxx xxxxxxxxx  2 u   88  256  377   19.418    2.451   0.666



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