NAME

ntpd − time synchronization daemon implementing NTP

SYNOPSIS

/usr/etc/ntpd [-a threshold] [-l] [-n] [-s]

OPTIONS

-a threshold is used to set the threshold which limits how far ntpd will change the system clock.  Its used as a sort of ultimate sanity check to prevent your system time from being changed a great deal.  By default, the threshold is 1000 seconds.  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, you would not specify this option  unless you wanted to gather statistical information to analyze the logical clock behavior.  If the -l option is specified, a message will be logged approximately every 2 minutes. 

-s will cause ntpd to never adjust the the local clock. 

DESCRIPTION

NTPD is the network time synchronization daemon and 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 accurracy and reliability.  Multiple time server masters may exist, but there is no requirement for election of a single master. 

Ntpd uses the adjtime(2) system call to slew the clock of the host by 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 NetManager application. 

The driftfile command can be used to specify the name of the file that the drift compensation register will be loaded from at initialization time and that updated values will be written into.  The drift compensation value describes the intrinsic drift of your host’s clock.  By default, the file /etc/ntp.drift will be used. 

Currently three time server specifications are supported.  They are master, clone and client. 

It is recommended that the bulk of the machines configured should be clients , as this will minimize resource usage on the remote NTP server.  If your host will be serving as a redistribution point for a cluster of hosts,  you should set it up as a clone or master server.  Configuration of servers is accomplished through the NetManager application. 

NOTES

Please choose your NTP servers carefully. 

BUGS

No doubt. 

FILES

/etc/ntp.drift  Stores local machines drift parameters.

SEE ALSO

adjtime(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.

ADAPATION TO NEXT AND NETINFO

Lee T. Tucker, NeXT Inc. 
 
 
 
 
 

LOCAL  —  9 December 1988