For small and larger offsets, ntpd will reject the reference time for a while. In the latter case the operation system’s clock will continue with the last corrections effective while the new reference time is being rejected. After some time, small offsets (significantly less than a second) will be slewed (adjusted slowly), while larger offsets will cause the clock to be stepped (set anew). Huge offsets are rejected, and ntpd will terminate itself, believing something very strange must have happened. To query NTP use one of the following commands:
In milliseconds: ntpq -p
In seconds: ntpdc -p
For example:
In milliseconds
root@ntp:~# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
-chris.magnet.ie 193.120.10.3 2 u 3 64 377 9.274 9.759 5.386
-tbag.heanet.ie .PPS. 1 u 1 64 277 196.163 6.444 5.583
-ec2-54-171-104- 129.242.4.241 2 u 61 64 377 10.696 11.281 4.481
-lanczos.maths.t 140.203.204.77 2 u 65 64 376 216.847 -0.980 4.405
+ntp1.tp.pl .ATOM. 1 u 60 64 377 242.321 -1.206 1.913
*tshirt.heanet.i .PPS. 1 u 61 64 377 218.342 -5.035 3.481
+time1.google.co 204.153.230.130 2 u 57 64 377 150.045 -1.029 2.885
-time2.google.co 224.240.179.50 2 u 58 64 377 163.618 -3.737 1.734
In seconds:
root@ntp:~# ntpdc -p
remote local st poll reach delay offset disp
=======================================================================
=time1.google.co 2001:470:1c:d7a 2 64 377 0.15004 -0.001029 0.06841
=ec2-54-171-104- 192.168.1.44 2 64 377 0.00960 0.009266 0.04362
=lanczos.maths.t 2001:470:1c:d7a 2 64 377 0.21426 0.014209 0.04640
*tbag.heanet.ie 2001:470:1c:d7a 1 64 277 0.19615 0.006444 0.05617
=ntp1.tp.pl 2001:470:1c:d7a 1 64 377 0.22079 0.005051 0.03702
=tshirt.heanet.i 2001:470:1c:d7a 1 64 377 0.20105 0.005399 0.04185
=time2.google.co 2001:470:1c:d7a 2 64 377 0.16360 -0.003737 0.07126
=chris.magnet.ie 192.168.1.44 2 64 377 0.00926 0.009759 0.04625