[ntp:questions] ntpd -x option

Matthias Fuchs matthias.fuchs at esd-electronics.com
Wed Mar 11 14:27:34 UTC 2009


Hi,

I am trying to understand ntpd's -x option. From the ntpd documentation
I expect ntpd to adjust the (system-)time in all situations when -x
is used. The only exception I see is when the system time is totally wrong
(more than 1000s) ntpd will see this as an error and exit. This can be
avoided through the "tinker panic 0" configuration.

Right?

But now, when I start ntpd with the -x option and an offset of
about 30s before ntpd is started, I get error messages like this

        frequency error 557 PPM exceeds tolerance 500 PPM

Also there seems to be not regulation at all and ntptime reports
errors:

~# ntptime
ntp_gettime() returns code 5 (ERROR)
  time cd624627.39886000  Wed, Mar 11 2009 15:16:07.224, (.224737),
  maximum error 993296 us, estimated error 16 us
ntp_adjtime() returns code 5 (ERROR)
  modes 0x0 (),
  offset 0.000 us, frequency 0.000 ppm, interval 1 s,
  maximum error 993296 us, estimated error 16 us,
  status 0x40 (UNSYNC),
  time constant 4, precision 1.000 us, tolerance 512 ppm,
~#

I am using two remote stratum 1 NTP servers for these tests.

So is there any way to make ntpd _adjust_ the time in all situations?
I am aware of the maximum adjustment of 500ppm (0.5ms/s). I would be lucky
if ntpd could adjust the above offset (30s) in a day or so.

I not want ntpd to step my system time! Not even once during initial
synchronisation.

ntpd is version ntpd 4.2.2p4 at 1.1585-o on Debian Etch for PowerPC.

I hope somebody can give me some hints.

Matthias





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