NAME¶
ntpd
—
Network Time Protocol daemon
SYNOPSIS¶
ntpd |
[ -dnSsv ]
[-f file ]
[-p file ] |
DESCRIPTION¶
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.
The options are as follows:
-d
- Do not daemonize. If this option is specified,
ntpd
will run in the foreground and log
to stderr.
-f
file
- Use file as the configuration file,
instead of the default
/etc/openntpd/ntpd.conf.
-n
- Configtest mode. Only check the configuration file for validity.
-p
file
- Write pid to file
-S
- Do not set the time immediately at startup. This is the default.
-s
- Try to set the time immediately at startup, as opposed to slowly adjusting
the clock.
ntpd
will stay in the
foreground for up to 15 seconds waiting for one of the configured NTP
servers to reply.
-v
- This option allows
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.
When
ntpd
starts up, it reads settings from
its configuration file, typically
ntpd.conf(5),
and its initial clock drift from
/var/lib/openntpd/ntpd.drift. Clock drift
is periodically written to the drift file thereafter.
FILES¶
- /etc/openntpd/ntpd.conf
- Default configuration file.
- /var/lib/openntpd/ntpd.drift
- Drift file.
- /var/lib/openntpd/run/ntpd.sock
- Socket file for communication with
ntpctl(8).
SEE ALSO¶
date(1),
adjfreq(2),
adjtime(2),
ntpd.conf(5),
ntpctl(8),
STANDARDS¶
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.
HISTORY¶
The
ntpd
program first appeared in
OpenBSD 3.6.