ntpdate(1M) System Administration Commands ntpdate(1M)NAMEntpdate - 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.
DESCRIPTIONntpdate 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(5) for descriptions of the following attributes:
┌────────────────────┬──────────────────────┐
│ 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 available 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 ALSOntpd(1M), ntpdc(1M), attributes(5)ntpdate(1M)
