[ntp:questions] ntp and date command

David Woolley david at djwhome.demon.co.uk
Thu Apr 5 06:52:00 UTC 2007

In article <4614337C.3070500 at comcast.net>,
Richard B. gilbert <rgilbert88 at comcast.net> wrote:

> It's a little less than clear what you hoped to accomplish by this and 

Making gross changes to the clock on a running machine is how people
think they can test that ntpd is synchronising the clock, when what they
should really be testing is the ability to track to 10ms, rather than
the ability to cope with bad operator training or hardware that is only
suitable for the scrapheap.

> wondering why ntpd (not xntpd for many years now BTW, the version that 

I believe he really is using xntpd, not the version of ntpd that is misnamed
as such.  Obviously he should upgrade.

> Ntpd will not "jump" your clock!  After you miss-set your clock by 600 

Normal configurations of ntpd will jump the clock if the error exceeds 128 ms,
but some vendors choose to set it into a slew only mode.  (The jump follows 
a sanity check that takes around quarter of an hour.)

> seconds, ntpd will attempt to correct your clock at its maximum slew 
> rate of 500 Parts Per Million or 1/2 millisecond per second. 

plus/minus the actual hardware clock frequency error!

More information about the questions mailing list