Operating system Linux How do I know if the "NTP" is working or not?

   How do I know if the "NTP" is working or not? 

     Well, there is a easy way to check it. It needs 4 steps to do, see following:

     STEP 1 (Test the current server):

          Try issuing the following command:

          $ ntpq -pn

           remote refid st t when poll reach delay offset jitter
           ===================================================
           tock.usno.navy 0.0.0.0 16 u - 64 0 0.000 0.000 4000.00

          The above is an example of a problem.
          Compare it to a working configuration.

          $ ntpq -pn

           remote refid st t when poll reach delay offset jitter
           ========================================================
           +128.4.40.12 128.4.40.10 2 u 107 128 377 25.642 3.350 1.012
           127.127.1.0 127.127.1.0 10 l 40 64 377 0.000 0.000 0.008
           +128.91.2.13 128.4.40.12 3 u 34 128 377 21.138 6.118 0.398
           *192.5.41.41 .USNO. 1 u 110 128 377 33.69 9.533 3.534

     STEP 2 (Configure the /etc/ntp.conf):

          $ cat /etc/ntp.conf

            # My simple client-only ntp configuration.
            server timeserver1.upenn.edu
            # ping -a timeserver1.upenn.edu shows the IP address 128.91.2.13
            # which is used in the restrict below
            restrict 128.91.2.13
            server tock.usno.navy.mil
            restrict 192.5.41.41
            server 128.4.40.12
            restrict 128.4.40.12
            server 127.127.1.0 # local clock
            fudge 127.127.1.0 stratum 10
            driftfile /etc/ntp/drift
            restrict default ignore
            restrict 127.0.0.0 mask 255.0.0.0
            authenticate no

     STEP 3 (Configure /etc/ntp/step-tickers):

          The values for server above are placed in the "/etc/ntp/step-tickers" file

          $ cat /etc/ntp/step-tickers

              timeserver1.upenn.edu
              tock.usno.navy.mil
              128.4.40.12

          The startup script /etc/rc.d/init.d/ntpd will grab the servers in this
          file and execute the ntpdate command as follows:

             /usr/sbin/ntpdate -s -b -p 8 timeserver1.upenn.edu

          Why? Because if the time is off ntpd will not start. The command above set the
          clock. If System Time deviates from true time by more than 1000 seconds, then,
          the ntpd daemon  will enter panic mode and exit.

     STEP 4 (Restart the service and check):

          Issue the restart command

            /etc/init.d/ntpd restart

          check the values for "ntpq -pn",
          which should match step 1.

             ntpq -pn


Operating system - Linux