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 ntpdate(1M)							 ntpdate(1M)




 NAME
      ntpdate - set the date and time via NTP

 SYNOPSIS
      ntpdate [ -Bbdpqsuv ] [ -a key# ] [ -e authdelay ] [ -k keyfile ]

	   [ -o version ] [ -p samples ] [ -t timeout ] server[ ... ]

 DESCRIPTION
      ntpdate sets the local date and time by polling those 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 the 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 xntpd.

      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 xntpd, 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 seconds, it will simply
      step the time by calling the clock_settime (see clocks(2)) system
      routine. If the error is less than 0.5 seconds, it will slew the time
      by calling the adjtime (see adjtime(2)) system 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 (see cron(1M))
      every hour or two.

      ntpdate will decline to set the date if an NTP server daemon (e.g.,
      xntpd) 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.

 COMMAND LINE OPTIONS
      ntpdate supports the following options:

      -a	     Enable the authentication function and specify the key
		     identifier to be used for authentication. The keys and
		     key identifiers must match in both the client and



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 ntpdate(1M)							 ntpdate(1M)




		     server key files. The default is to disable the
		     authentication function.

      -B	     Force the time to always be slewed using the adjtime
		     system call, even if the measured offset is greater
		     than +-128 ms. The default is to step the time using
		     the clock_settime system call if the offset is greater
		     than +-128 ms. Note that, if the offset is much greater
		     than +-128 ms it can take a long time (hours) to slew
		     the clock to the correct value. During this time the
		     host should not be used to synchronize clients.

      -b	     Force the time to be stepped using the clock_settime
		     system call, rather than slewed (default) using the
		     adjtime system call. This option should be used when
		     called from a startup file at boot time.

      -d	     Enable the debugging mode, in which ntpdate will go
		     through all the steps, but not adjust the local clock.
		     Information useful for general debugging will also be
		     printed.

      -e authdelay   Specify the processing delay to perform an
		     authentication function as the value authdelay, in
		     seconds and fraction (see xntpd(1M) for details). This
		     number is usually small enough to be negligible for
		     most purposes, though specifying a value may improve
		     timekeeping on very slow CPU's.

      -k keyfile     Specify the path for the authentication key file as the
		     string keyfile.  The default is /etc/ntp.keys.  This
		     file should be in the format described in xntpd.

      -o version     Specify the NTP version for outgoing packets as the
		     integer version, which can be 1 or 2.  The default is
		     3. This allows ntpdate to be used with older NTP
		     versions.

      -p samples     Specify the number of samples to be acquired from each
		     server as the integer samples, with values from 1 to 8
		     inclusive. The default is 4.

      -q	     Prints the offset measurement, stratum of the server(s)
		     and delay measurement without adjusting the local
		     clock. This is similar to -d option which gives a more
		     detailed debugging information.

      -s	     Divert logging output from the standard output
		     (default) to the system syslog (see syslog(3C))
		     facility. This is designed primarily for convenience of
		     cron scripts.



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 ntpdate(1M)							 ntpdate(1M)




      -t timeout     Specify the maximum waiting time for a server response
		     as the value timeout, in seconds and fraction. The
		     value is rounded to a multiple of 0.2 seconds. The
		     default is 1 second, a value suitable for polling
		     across a LAN.

      -u	     Direct ntpdate 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.

      -v	     Prints the NTP version number and the offset
		     measurement information.

 FILES
      /etc/ntp.keys	       Contains the encryption keys used by ntpdate.

 SEE ALSO
      adjtime(2), clocks(2), cron(1M), syslog(3C), ntpq(1M), xntpd(1M),
      xntpdc(1M).

      DARPA Internet Request For Comments RFC1035 Assigned Numbers.

 AUTHOR
      ntpdate was developed by Dennis Ferguson at the University of Toronto.




























 Hewlett-Packard Company	    - 3 -   HP-UX Release 11i: November 2000