ntpdate man page on DigitalUNIX

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ntpdate(8)							    ntpdate(8)

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

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

       Tells ntpdate to step the system time immediately  to  match  NTP.  Use
       this  option  only  when	 booting the system.  Prints configuration and
       debugging information.  Queries the server(s) and prints	 the  informa‐
       tion received; the date and time are not set.  Tells ntpdate to log its
       actions through the syslog(3) facility rather than to the standard out‐
       put.  This is useful when running the program from cron(8).  Tells ntp‐
       date to use an unprivileged port to send the packets from. This is use‐
       ful  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.  Runs
       in verbose mode.	 Specifies that all packets  should  be	 authenticated
       using  the key number provided.	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.   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).   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 ver‐
       sion 3 queries.	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.  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.

       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 off‐
       set 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 exam‐
       ple,  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.


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

       A common problem is polling a server using the wrong query version num‐
       ber 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 follow‐
       ing message: WARNING:  ntpdate cannot succeed, please check your
	 NTP configuration

       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 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

       Specifies the command path Contains the encryption keys used by ntpdate

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

       Files: ntp.conf(4)


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