22.13. Checking the Status of NTP

To check if ntpd is configured to run at system start, issue the following command:
~]$ chkconfig --list ntpd
ntpd           	0:off	1:off	2:on	3:on	4:on	5:on	6:off
By default, when ntpd is installed, it is configured to start at every system start.
To check if ntpd is running, issue the following command:
~]$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+clock.util.phx2 .CDMA.           1 u  111  128  377  175.495    3.076   2.250
*clock02.util.ph .CDMA.           1 u   69  128  377  175.357    7.641   3.671
 ms21.snowflakeh .STEP.          16 u    - 1024    0    0.000    0.000   0.000
 rs11.lvs.iif.hu .STEP.          16 u    - 1024    0    0.000    0.000   0.000
 2001:470:28:bde .STEP.          16 u    - 1024    0    0.000    0.000   0.000
The command lists connected time servers and displays information indicating when they were last polled and the stability of the replies. The column headings are as follows:
  • remote and refid: remote NTP server, and its NTP server
  • st: stratum of server
  • t: type of server (local, unicast, multicast, or broadcast)
  • poll: how frequently to query server (in seconds)
  • when: how long since last poll (in seconds)
  • reach: octal bitmask of success or failure of last 8 queries (left-shifted); 377 = 11111111 = all recent queries were successful; 257 = 10101111 = 4 most recent were successful, 5 and 7 failed
  • delay: network round trip time (in milliseconds)
  • offset: difference between local clock and remote clock (in milliseconds)
  • jitter: difference of successive time values from server (high jitter could be due to an unstable clock or, more likely, poor network performance)
To obtain a brief status report from ntpd, issue the following command:
~]$ ntpstat
unsynchronised
  time server re-starting
   polling server every 64 s
~]$ ntpstat
synchronised to NTP server (10.5.26.10) at stratum 2
   time correct to within 52 ms
   polling server every 1024 s