[ntp:questions] ntpd executable -x option

David Woolley david at ex.djwhome.demon.invalid
Wed Apr 11 22:29:15 UTC 2012


Nick G wrote:

> True or False or Insufficient-Data:
> According to the man page and doc.ntp.org, "kernel time discipline is
> disabled" if my local ntpd uses "-x". So if my local ntpd loses its
> one-and-only parent NTP server, the local ntpd will no longer enforce
> any discipline whatsoever on the local clock. In other words, my local
> ntpd is literally doing nothing, just consuming a little RAM and a few
> cycles every now and then.

False.  It will continue to use the user space time discipline it has 
been using all along.  This has a one second sawtooth, so is not as 
accurate as the kernel space discipline, which applies corrections on 
every clock interrupt.  However, it will still apply the last known 
frequency correction.

Stricly speaking, -x is equivalent to tinkering with a very large value 
for the offset before ntpd will step, and it is that large value that 
actually forces the fallback to the user space time discipline.



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