Manual Pages for UNIX Operating System command usage for man ntpdate

System Administration Commands                        ntpdate(1M)



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 identifiers must match in both the  client
          and server key files. The default is to disable authen-
          tication.

     -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  offset 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  authentica-
          tion  function  as  the value authdelay, in seconds and
          fraction (see ntpd 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/inet/ntp.keys. This



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System Administration Commands                        ntpdate(1M)



          file should be in the format described in ntpd.

     -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   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  Protocol (NTP) server(s) given as the server arguments
     to determine the correct 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  relia-
     bility  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 substitute for the
     NTP  daemon, which uses sophisticated algorithms to maximize
     accuracy and  reliability  while  minimizing  resource  use.



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System Administration Commands                        ntpdate(1M)



     Finally,  since  ntpdate  does not discipline the host clock
     frequency as does ntpd, the accuracy using ntpdate  is  lim-
     ited.

     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  adj-
     time()  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 regu-
     lar 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.   Note  that
     in  contexts  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(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________
    |   ATTRIBUTE TYPE   |    ATTRIBUTE VALUE   |
    |____________________|_______________________|_
    | Availability       |  service/network/ntp |
    |____________________|_______________________|_
    | Interface Stability|  Uncommitted Obsolete|
    |____________________|______________________|

NOTES
     Source      for      ntpdate      is      available       on
     http://src.opensolaris.org.

     Disclaimer: The functionality of this program is now  avail-
     able  in the ntpd program. See the -q command line option in
     the ntpd - Network Time  Protocol  (NTP)  daemon  man  page.
     After  a  suitable  period,  the  ntpdate  program  is to be
     retired from this distribution

SEE ALSO
     ntpd(1M), ntpdc(1M), attributes(5)









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