| NTPDATE(8) | System Manager's Manual | NTPDATE(8) | 
ntpdate —
| ntpdate | [ -bBdoqsuv] [-akey] [-eauthdelay] [-kkeyfile] [-oversion] [-psamples] [-ttimeout] [server ...] | 
ntpdate sets the local date and time by polling the
  Network Time Protocol (NTP) server(s) given as the
  server arguments to determine the correct time. It must
  be run as root on the local host. A number of samples are obtained from each
  of the servers specified and a subset of the NTP clock filter and selection
  algorithms are applied to select the best of these. Note that the accuracy and
  reliability of ntpdate depends on the number of
  servers, the number of polls each time it is run and the interval between
  runs.
ntpdate can be run manually as necessary
    to set the host clock, or it can be run from the host startup script to set
    the clock at boot time. This is useful in some cases to set the clock
    initially before starting the NTP daemon ntpd. It is
    also possible to run ntpdate from a
    cron script. However, it is important to note that
    ntpdate with contrived cron
    scripts is no substitute for the NTP daemon, which uses sophisticated
    algorithms to maximize accuracy and reliability while minimizing resource
    use. Finally, since ntpdate does not discipline the
    host clock frequency as does ntpd, the accuracy
    using ntpdate is limited.
Time adjustments are made by ntpdate in
    one of two ways. If ntpdate determines the clock is
    in error more than 0.5 second it will simply step the time by calling the
    system settimeofday(2)
    routine. If the error is less than 0.5 seconds, it will slew the time by
    calling the system adjtime(2)
    routine. The latter technique is less disruptive and more accurate when the
    error is small, and works quite well when ntpdate is
    run by cron every hour or two.
ntpdate will decline to set the date if an
    NTP server daemon (e.g., ntpd ) is running on the
    same host. When running ntpdate on a regular basis
    from cron as an alternative to running a daemon,
    doing so once every hour or two will result in precise enough timekeeping to
    avoid stepping the clock.
If NetInfo support is compiled into
    ntpdate, then the server
    argument is optional if ntpdate can find a time
    server in the NetInfo configuration for ntpd
-a
    keyntpdate. The keys and key identifiers must match
      in both the client and server key files. The default is to disable the
      authentication function.-B-b-dntpdate will
      go through all the steps, but not adjust the local clock. Information
      useful for general debugging will also be printed.-e
    authdelay-k
    keyfile-o
    versionntpdate to be used with older NTP
      versions.-p
    samples-q-s-t
    timeout-untpdate to use an unprivileged port for
      outgoing packets. This is most useful when behind a firewall that blocks
      incoming traffic to privileged ports, and you want to synchronise with
      hosts beyond the firewall. Note that the -d option
      always uses unprivileged ports.-vntpdate string
      to be logged.ntpdate.| January 28, 2010 | NetBSD 9.4 |