NTPD(8) | System Manager's Manual | NTPD(8) |
ntpd
— Network
Time Protocol daemon
ntpd |
[-dnSsv ]
[-f file] |
The ntpd
daemon synchronizes the local
clock to one or more remote NTP servers or local timedelta sensors.
ntpd
can also act as an NTP server itself,
redistributing the local time. It implements the Simple Network Time
Protocol version 4, as described in RFC 5905, and the Network Time Protocol
version 3, as described in RFC 1305. Time can also be fetched from TLS HTTPS
servers to reduce the impact of unauthenticated NTP man-in-the-middle
attacks.
The options are as follows:
-d
ntpd
will run in the foreground and log to
stderr.-f
file-n
-S
-s
ntpd
will stay in the foreground for up
to 15 seconds waiting for one of the configured NTP servers to reply.-v
ntpd
to send DEBUG priority
messages to syslog.ntpd
uses the
adjtime(2) system call to
correct the local system time without causing time jumps. Adjustments of
32ms and greater are logged using
syslog(3). The threshold
value is chosen to avoid having local clock drift thrash the log files.
Should ntpd
be started with the
-d
or -v
option, all calls
to adjtime(2) will be
logged.
After the local clock is synchronized,
ntpd
adjusts the clock frequency using the
adjfreq(2) system call to
compensate for systematic drift.
ntpd
is usually started at boot time, and
can be enabled by setting ntpd_flags in
/etc/rc.conf.local. See
rc(8) and
rc.conf(8) for more
information on the boot process and enabling daemons.
When ntpd
starts up, it reads settings
from its configuration file, typically
ntpd.conf(5), and its
initial clock drift from /var/db/ntpd.drift. Clock
drift is periodically written to the drift file thereafter.
date(1), adjfreq(2), adjtime(2), ntpd.conf(5), ntpctl(8), rc(8), rc.conf(8), rdate(8)
David L. Mills, Network Time Protocol (Version 3): Specification, Implementation and Analysis, RFC 1305, March 1992.
David L. Mills, Jim Martin, Jack Burbank, and William Kasch, Network Time Protocol Version 4: Protocol and Algorithms Specification, RFC 5905, June 2010.
The ntpd
program first appeared in
OpenBSD 3.6.
October 30, 2015 | OpenBSD-6.0 |