[ntp:questions] NTP.log interpretation

Steve Kostecke kostecke at ntp.org
Fri Apr 18 19:01:12 UTC 2014

On 2014-04-18, William Unruh <unruh at invalid.ca> wrote:

> On 2014-04-18, GregL <greg.leibfried at gmail.com> wrote:
>> Now, I'm just planning on making changes to the ntp.conf, like adding
>> the "-x" parameter. I'm hoping that that will prevent huge time
>> resets backwards in time...should that ever be even possible again.
> ntpd will reset the time if it is off by more than 128 ms.

The default step threshold is 128ms. This threshold is user

As for the '-x' option. Using it could lead to having a clock so far off
from the correct time that ntpd will never be able to correct the offset
via slewing. 

> Those higly non-linear jumps are one of the "features" of ntpd. If you
> do not want them, run for example chrony. It will smoothly change the
> time. It will however also at times slew the time much faster than
> 500PPM to get the time back on track.

500PPM per day is 43 seconds per day. One could argue that a clock which
requires more than 43 seconds per day of correction is fundamentally
broken and requires repair rather than calibration.

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

More information about the questions mailing list