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

matthew.garman at gmail.com matthew.garman at gmail.com
Fri May 31 13:36:39 UTC 2013

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?

> > 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.

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