MacOS – How to get exact NTP drift in OS X

macosntp

I'm trying to get actual NTP drift on Macs connected to a local NTP server.

  • When reading /var/db/ntp.drift file I get -37.521 which according to PPM to milliseconds conversion gives -3241ms of drift.

  • When using ntpq -c lpeer I get something like this:

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*172-1-1-5.light 164.67.62.212    2 u   57   64  377  199.438   38.322  29.012

which gives me offset of 38.322ms

  • Finally, sntp 172.1.1.5 outpus this:
2016 Jan 21 18:41:45.248591 +0.019244 +/- 0.022507 secs

which says having about 19ms of drift.

I'm confused which one the approaches gives accurate NTP drift?

Best Answer

sntp gives the current offset. The ntp.drift file is updated only occasionally, I think when the daemon starts.

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