Go to main content

man pages section 8: System Administration Commands

Exit Print View

Updated: Thursday, June 13, 2019
 
 

ntpdate (8)

Name

ntpdate - set the date and time with NTP

Synopsis

/usr/sbin/ntpdate [-46bBdqsuv] [-a key] [-e Authdelay] [-k keyfile] [-o
version] [-p samples] [-t timeout] server [ ... ]

Description

System Administration Commands                                      ntpdate(8)



NAME
       ntpdate - set the date and time with NTP

SYNOPSIS
       /usr/sbin/ntpdate [-46bBdqsuv] [-a key] [-e Authdelay] [-k keyfile] [-o
       version] [-p samples] [-t timeout] server [ ... ]

OPTIONS
       -4     Force DNS resolution of following host names on the command line
              to the IPv4 namespace.

       -6     Force DNS resolution of following host names on the command line
              to the IPv6 namespace.

       -a key Enable authentication and specify the key identifier to be  used
              for authentication as the argument key. The keys and key identi-
              fiers must match in both the client and server  key  files.  The
              default is to disable authentication.

       -B     Force  the  time  to always be slewed using the adjtime() system
              call, even if the measured offset is greater than  0.5  seconds.
              The default is to step the time using settimeofday() if the off-
              set is greater than +-0.5s. Note that, if  the  offset  is  much
              greater  than  +-0.5s in this case, that 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 settimeofday() 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  func-
              tion  as  the value authdelay, in seconds and fraction (see ntpd
              for details). This number is usually small enough to be negligi-
              ble  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/inet/ntp.keys. This file should be
              in the format described in ntpd.

       -o version
              Specify the NTP version for outgoing packets as the integer ver-
              sion, 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     Query only - don't set the clock.

       -s     Divert logging output from the standard output (default) to  the
              system syslog facility.

       -t timeout
              Specify  the  maximum  time waiting for a server response as the
              value timeout, in seconds and fraction. The value is 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 or 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     Print ntpdate's version  identification  string  during  program
              startup.

DESCRIPTION
       ntpdate sets the local date and time by polling the Network Time Proto-
       col (NTP) server(s) given as the server arguments to determine the cor-
       rect time. It must be run as root unless the -d or -q options are used.
       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.
       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 sub-
       stitute for the NTP daemon, which uses sophisticated algorithms to max-
       imize  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() routine. If the
       error is less than 0.5 seconds, it will slew the time  by  calling  the
       system  adjtime()  routine. The latter technique is less disruptive and
       more accurate when the error is small, and works quite well  when  ntp-
       date 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  pre-
       cise enough timekeeping to avoid stepping the clock.  Note that in con-
       texts where a host name is expected, a -4 qualifier preceding the  host
       name  forces DNS resolution to the IPv4 namespace, while a -6 qualifier
       forces DNS resolution to the IPv6 namespace.

ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+----------------------+
       |ATTRIBUTE TYPE |   ATTRIBUTE VALUE    |
       +---------------+----------------------+
       |Availability   | service/network/ntp  |
       +---------------+----------------------+
       |Stability      | Uncommitted obsolete |
       +---------------+----------------------+
NOTES
       Disclaimer: The functionality of this program is now available  in  the
       ntpd program. See the -q command line option in the ntpd - Network Time
       Protocol (NTP) daemon man page. The ntpdate program is  to  be  retired
       from this distribution.

SEE ALSO
       ntpd(8), attributes(7)


       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source          was         downloaded         from          http://ar-
       chive.ntp.org/ntp4/ntp-4.2/ntp-4.2.8p13.tar.gz

       Further information about this software can be found on the open source
       community website at http://www.ntp.org/.



                                                                    ntpdate(8)