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 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
           + 2 u 107 128 377 25.642 3.350 1.012
  10 l 40 64 377 0.000 0.000 0.008
           + 3 u 34 128 377 21.138 6.118 0.398
           * .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
            # which is used in the restrict below
            server tock.usno.navy.mil
            server # local clock
            fudge stratum 10
            driftfile /etc/ntp/drift
            restrict default ignore
            restrict mask
            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


          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