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ntpdate(8)
NAME
  ntpdate - set the date and time via NTP (Network Time Protocol)

SYNOPSIS
  /usr/sbin/ntpdate [-bdqsuv] [-a key#] [-e authdelay] [-k keyfile] [-o
  version] [-p samples] [-t timeout] server1 server2 server3...

OPTIONS
  -b  Tells ntpdate to step the system time immediately to match NTP. Use
      this option only when booting the system.

  -d  Prints configuration and debugging information.

  -q  Queries the server(s) and prints the information received; the date and
      time are not set.

  -s  Tells ntpdate to log its actions through the syslog(3) facility rather
      than to the standard output.  This is useful when running the program
      from cron(8).

  -u  Tells ntpdate to use an unprivileged port to send the packets from.
      This is useful when you are 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  Runs in verbose mode.

  -a key#
      Specifies that all packets should be authenticated using the key number
      provided.

  -e authdelay
      Specifies an authentication processing delay, in seconds (see xntpd(8)
      for details). This number is usually small enough to be negligible for
      ntpdate's purposes, though specifying a value may improve timekeeping
      on very slow CPU's.

  -k keyfile
      Specifies that authentication keys will be read from keyfile instead of
      the default /etc/ntp.keys file.  This file should be in the format
      described in xntpd(8).

  -o version
      Forces ntpdate to poll as a version implementation. By default ntpdate
      claims to be an NTP version 3 implementation in its outgoing packets.
      Some older software will decline to respond to version 3 queries.

  -p samples
      Acquires a specified number of samples from each server. The range of
      values for samples is from 1 and 8, inclusive.  The default is 4.

  -t timeout
      Waits timeout seconds for a response. Any value entered will be rounded
      to a multiple of 0.2 seconds.  The default is 1 second, a value
      suitable for polling across a LAN.

DESCRIPTION
  The ntpdate command sets the local date and time by polling the Network
  Time Protocol server(s) on the host(s) given as 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 the standard
  NTP clock filter and selection algorithms are applied to select the best of
  these.  The ntpdate command is run from /sbin/init.d/settime to set the
  time of day at boot time, if NTP is configured.  (See Network
  Administration: Services for information on configuring NTP.) Note that
  ntpdate's reliability and precision will improve dramatically with greater
  numbers of servers.  While a single server may be used, better performance
  and integrity will be obtained by providing at least three or four servers,
  if not more.

  Time adjustments are made by ntpdate in one of the following ways:

    ·  If ntpdate determines your clock is off by more than 0.5 seconds, it
       steps the time by calling settimeofday(2).

    ·  If the error is less than 0.5 seconds, however, it will by default
       slew the clock's time by a call to adjtime(2) with the offset.

  The latter technique is less disruptive and more accurate when the offset
  is small, and works quite well when ntpdate is run by cron every hour or
  two. The adjustment made in the latter case is actually 50% larger than the
  measured offset since this will tend to keep a badly drifting clock more
  accurate (at some expense to stability, though this tradeoff is usually
  advantageous).

  Ntpdate will decline to set the date if an NTP server daemon (for example,
  xntpd(8)) is running on the same host.  When running ntpdate on a regular
  basis from cron(8) 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.

				     Note

       Because of significant changes in NTP version 3, you should check all
       scripts that use the ntpdate command for correct usage and output.

ERRORS
  A common problem is polling a server using the wrong query version number
  or wrong authentication key.	If either occurs, ntpdate prints the
  following error message:

       18 Apr 10:20:28	ntpdate(1192]: no server
	 suitable for synchronization found

  At boot time, if NTP is not configured, the ntpdate prints the following
  message:

       WARNING:	 ntpdate cannot succeed, please check your
	 NTP configuration

EXAMPLES
   1.  The following command line sets the date and time after polling server
       host1.dec.com as a version 2 implementation:
	    /usr/sbin/ntpdate -o 2 host1.dec.com

   2.  The following command line sets the date and time after polling server
       host2.dec.com.  All packets are authenticated using authentication key
       1.
	    /usr/sbin/ntpdate -a 1 host2.dec.com

FILES
  /usr/bin/ntpdate
      Specifies the command path

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

SEE ALSO
  Commands: ntpq(8), xntpd(8), xntpdc(8)

  Files: ntp.conf(4)

Index for Section 8

Alphabetical listing for N

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