NTPD(8)NTPD(8)NAMEntpd - time synchronization daemon implementing NTP
SYNOPSIS
/usr/etc/ntpd [-a threshold] [-l] [-n] [-s]
OPTIONS-a threshold is used to set the threshold, limiting how far ntpd will
change the system clock. It is used to prevent the system time from
being changed a great deal. By default, the threshold is 1000 seconds.
The threshold is to be specified in units of seconds, or the string any
to defeat the sanity check.
-l will cause ntpd to log a message each time the logical clock is
changed. Normally, do not specify this option except to gather
statistical information for analyzing the logical clock behavior. If
the -l option is specified, a message will be logged approximately
every 2 minutes.
-s will prevent ntpd from adjusting the local clock.
DESCRIPTION
The ntpd network time synchronization daemon is normally invoked at
boot time from the /etc/rc(8) file. It implements the version of the
Network Time Protocol described in RFC-1059. It maintains the host's
time, synchronized with a set of distributed time servers, each with
varying accuracy and reliability. Multiple time server masters may
exist, but there is no requirement for election of a single master.
The ntpd daemon uses adjtime(2) to adjust the clock of the host by a
small amount in order to keep the clock synchronized. If the local
clock exceeds the ``correct'' time by some threshold, then
settimeofday(2) is used to make a step adjustment of the local clock.
When ntpd(8) is started on the machine, it reads configuration
information from netinfo, which contains information about other ntp
time servers and host specific information. Configuration information
is created and managed by the HostManager application.
The driftfile command can be used to specify the name of the file from
which the drift compensation register will be loaded at initialization
time, and to which updated values will be written. The drift
compensation value describes the intrinsic drift of the host clock. By
default, the file /etc/ntp.drift is used.
Currently, three time server specifications are supported: master,
clone and client.
It is recommended that the bulk of the machines configured should be
clients, as this will minimize resource demand on the remote NTP
server. If the host will be serving as a redistribution point for a
cluster of hosts, it should be set up as a clone or master server.
Configuration of servers is accomplished through the HostManager
application.
NOTES
Please choose NTP servers carefully.
BUGS
No doubt.
FILES
/etc/ntp.drift Stores local machines drift parameters.
SEE ALSOadjtime(2), settimeofday(2),
RFC-1059 Network Time Protocol(1), Mills, D.L.
AUTHORS
Louis A. Mamakos, louie@TRANTOR.UMD.EDU
Michael G. Petry, petry@TRANTOR.UMD.EDU
The University of Maryland Computer Science Center.
ADAPTATION TO NEXT AND NETINFO
Lee T. Tucker, NeXT Computer, Inc.
9 December 1988 NTPD(8)
