NTP Toolkit

Linux System Administrators Guide:
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# 14.7. NTP Toolkit

There are a number of utilities available to check if NTP is doing it's job. The ntpq -p command will print out your system's current time status.

    # ntpq -p
         remote           refid      st t when poll reach   delay   offset  jitter
    ==============================================================================
    *cudns.cit.corne ntp0.usno.navy.  2 u  832 1024  377   43.208    0.361   2.646
     LOCAL(0)        LOCAL(0)        10 l   13   64  377    0.000    0.000   0.008

The ntpdc -c loopinfo will display how far off the system time is in seconds, based upon the last time the remote server was contacted.

    # ntpdc -c loopinfo
    offset:               -0.004479 s
    frequency:            133.625 ppm
    poll adjust:          30
    watchdog timer:       404 s

ntpdc -c kerninfo will display the current remaining correction.

    # ntpdc -c kerninfo
    pll offset:           -0.003917 s
    pll frequency:        133.625 ppm
    maximum error:        0.391414 s
    estimated error:      0.003676 s
    status:               0001  pll
    pll time constant:    6
    precision:            1e-06 s
    frequency tolerance:  512 ppm
    pps frequency:        0.000 ppm
    pps stability:        512.000 ppm
    pps jitter:           0.0002 s
    calibration interval: 4 s
    calibration cycles:   0
    jitter exceeded:      0
    stability exceeded:   0
    calibration errors:   0

A slightly more different version of ntpdc -c kerninfo is ntptime

    # ntptime
    ntp_gettime() returns code 0 (OK)
      time c35e2cc7.879ba000  Thu, Nov 13 2003 11:16:07.529, (.529718),
      maximum error 425206 us, estimated error 3676 us
    ntp_adjtime() returns code 0 (OK)
      modes 0x0 (),
      offset -3854.000 us, frequency 133.625 ppm, interval 4 s,
      maximum error 425206 us, estimated error 3676 us,
      status 0x1 (PLL),
      time constant 6, precision 1.000 us, tolerance 512 ppm,
      pps frequency 0.000 ppm, stability 512.000 ppm, jitter 200.000 us,
      intervals 0, jitter exceeded 0, stability exceeded 0, errors 0.

Yet another way to see how well NTP is working is with the ntpdate -d command. This will contact an NTP server and determine the time difference but not change your system's time.

    # ntpdate -d 132.236.56.250
    13 Nov 14:43:17 ntpdate[29631]: ntpdate 4.1.1c-rc1@1.836 Thu Feb 13 12:17:20 EST 2003 (1)
    transmit(132.236.56.250)
    receive(132.236.56.250)
    transmit(132.236.56.250)
    receive(132.236.56.250)
    transmit(132.236.56.250)
    receive(132.236.56.250)
    transmit(132.236.56.250)
    receive(132.236.56.250)
    transmit(132.236.56.250)
    server 132.236.56.250, port 123
    stratum 2, precision -17, leap 00, trust 000
    refid [192.5.41.209], delay 0.06372, dispersion 0.00044
    transmitted 4, in filter 4
    reference time:    c35e5998.4a46cfc8  Thu, Nov 13 2003 14:27:20.290
    originate timestamp: c35e5d55.d69a6f82  Thu, Nov 13 2003 14:43:17.838
    transmit timestamp:  c35e5d55.d16fc9bc  Thu, Nov 13 2003 14:43:17.818
    filter delay:  0.06522  0.06372  0.06442  0.06442
             0.00000  0.00000  0.00000  0.00000
    filter offset: 0.000036 0.001020 0.000527 0.000684
             0.000000 0.000000 0.000000 0.000000
    delay 0.06372, dispersion 0.00044
    offset 0.001020

    13 Nov 14:43:17 ntpdate[29631]: adjust time server 132.236.56.250 offset 0.001020 sec

If you want actually watch the system synchronize you can use ntptrace.

    # ntptrace 132.236.56.250
    cudns.cit.cornell.edu: stratum 2, offset -0.003278, synch distance 0.02779
    truetime.ntp.com: stratum 1, offset -0.014363, synch distance 0.00000, refid 'ACTS'

If you need your system time synchronized immediately you can use the ntpdate remote-servername to force a synchronization. No waiting!

    # ntpdate 132.236.56.250
    13 Nov 14:56:28 ntpdate[29676]: adjust time server 132.236.56.250 offset -0.003151 sec

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