set the date and time via NTP
ntpdate [-bBdqsuv] [-a key]
[-e authdelay] [-k keyfile]
[-t timeout] server [...]
ntpdate sets the local date and time by polling the Network Time Protocol
(NTP) server(s) given as the server arguments to determine the
It must be run as root on the local host. 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. This is
useful in some cases to set the clock initially before starting the NTP
It is also possible to run ntpdate from a cron script.
However, it is important to note that ntpdate with contrived
no substitute for the NTP daemon, which uses sophisticated algorithms to
maximize 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
routine. If the error is less
than 0.5 seconds, it will slew the time by calling the system
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
In the latter case, the slew adjustment is actually 50% larger than the measured offset, since
this will tend to keep a badly drifting clock more accurate.
ntpdate will decline to set the date if an NTP server daemon (for example, 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 precise enough timekeeping to avoid stepping the clock.
ntpdate takes the following options:
Enable the authentication function 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 the authentication function.
Force the time always to be slewed using the adjtime system call,
even if the measured offset is greater than ±128ms. The default is to
step the time using settimeofday if the offset is greater than
±128ms. Note that, if the offset is much greater than ±128ms
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
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.
Enable the debugging mode, in which ntpdate will go through all the
steps, but do not adjust the local clock. Information useful for general
debugging will also be printed.
Specify the processing delay to perform an authentication function as
the value authdelay, in seconds and fraction (see
This number is usually small enough to be negligible for most purposes,
though specifying a value may improve timekeeping on very slow CPUs.
Specify the path for the authentication key file as the string keyfile.
The default is /etc/ntp.keys. This file should be in the format
described on the
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.
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.
Query only - do not set the clock.
The interval (in seconds) to spend measuring the drift rate.
Divert logging output from the standard output (default) to the system
facility. This is designed primarily for convenience of cron
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.
Direct ntpdate to use an unprivileged port for 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.
Verbose option. Causes the ntpdate version identification
string to be logged.
encryption keys used by ntpdate
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003