2015-10-06 Testing NTP server under OS X

When you configure a different time server (NTP server) under OS X, the System Settings panel doesn't actually tell you that the address is valid or not. To check this, open a terminal window and use the ntpq command as follows:

 $ ntpq -p ntp1.example.com

The time server should list its sources and the command should display something roughly as follows:

      remote           refid      st t when poll reach   delay   offset  jitter
 ==============================================================================
 +kl10abav.xx.xxx 193.79.237.14    2 u 1030 1024  377    1.904    4.659   0.150
 -kl10ab9n.xx.xxx 193.79.237.14    2 u  924 1024  377    1.805    4.721   0.100
 *ntp1qvi.xxxxxxx .GPS.            1 u  921 1024  377   24.874   -1.048   0.330
 +ntp1tls.xxxxxxx .GPS.            1 u  705 1024  377   28.317   -1.072   0.211

If there isn't actually a time server running, then ntpq will report:

 nodename nor servname provided, or not known