ntp.conf(4) CLIX ntp.conf(4)
NAME
ntp.conf - Network Time Protocol (NTP) configuration file
DESCRIPTION
When the ntpd daemon is started on the machine, it reads configuration
information from the file /etc/ntp.conf (or the configuration file
specified with the ntpd -c flag). All action taken by the ntpd daemon is
defined in the configuration file. Configuration information is listed
one entry per line, with fields separated by blank spaces. Lines
beginning with a number sign (#) are treated as comments.
The configuration file contains two major types of information: local host
information and remote time server specifications. The local host
information describes the intrinsic properties of the clock on the local
host. The commands in this group are: debuglevel, driftfile, precision,
setthreshold, and trusting.
The debuglevel command specifies a value the debug level is set to. (This
command overrides the -D flag.)
The driftfile command is used to specify the name of the file from which
the drift compensation register is loaded at initialization time, and to
which updated values are written. The drift compensation value describes
the intrinsic drift of the clock on the local host. By default, the
/etc/ntp.drift file is used.
The precision command takes a number that describes the resolution of the
local clock, as a power of two. For example, a CLIX system typically has
a 60 Hz clock. Thus, a precision of -6 should be specified with this
command.
The setthreshold command accepts either a value to set the threshold in
seconds, or the string any to defeat the sanity check. This command
overrides the ntpd -a flag. (For more information, refer to the
description of the -a flag in ntpd(8).)
The trusting command accepts the string yes or no, or the value 1 or 0.
If yes or 1 is specified, ntpd on the local host is willing to synchronize
to a remote NTP server not specified in this configuration file. If no or
0 is specified, ntpd will not synchronize the local host to such a server.
By default, the NTP daemon on the local host is willing to synchronize to
a nonconfigured NTP server.
Currently three types of time server specifications are supported. They
are peer, server, and passive. These three commands specify hosts the
local daemon is willing to synchronize to. If an NTP packet is received
from a host not specified on one of these commands, the local daemon may
not be willing to synchronize to it (see the trusting command in the
previous paragraph). Each command takes either an Internet address or a
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ntp.conf(4) CLIX ntp.conf(4)
hostname.
The peer and server commands cause the local daemon to poll other NTP time
servers. For a host specified with a peer command, the local daemon sends
NTP packets in Symmetric-Active mode, indicating the local NTP time server
is willing to synchronize or be synchronized by the NTP time server on the
remote host. For a host specified with a server command, the local daemon
sends NTP packets in Client mode, indicating the local NTP time server is
willing to be synchronized by the NTP time server on the remote host.
When the local NTP daemon loses contact with a host specified with a peer
or server command, the daemon continues to poll to contact the remote host
again.
The passive command allows the local daemon to accept polls from other NTP
time servers. On receipt of NTP packets from a host specified with a
passive command, the local daemon sends back NTP packets in Symmetric-
Passive mode, indicating the local NTP time server is willing to
synchronize or be synchronized by the NTP time server on the remote host.
A host specified with a passive command is never polled. If the remote
host begins to poll the local NTP daemon, it is eligible to be
synchronized but is not polled if the local NTP daemon loses contact with
it.
If the local host redistributes time values to a cluster of hosts, the
configuration file should contain either server specifications for higher
quality clocks (lower stratums) or a peer specification for a reference
clock (see the following paragraph). This file might also contain peer
specifications for other equal stratum clocks and passive specifications
for lower quality clocks (higher stratums). If the local host does not
redistribute time values to other hosts, this file should contain only
server specifications.
If the local host has a reference clock, the configuration file should
contain a special peer specification like the one in the sample file in
the EXAMPLES section. The first field after the peer keyword is the name
of the file the clock is connected to. This field must be a complete
pathname. The next field is the reference-id which are inserted into the
packets generated from the local NTP daemon. For a PSTI clock, this field
should be either WWV, WWVB, or GOES. For a local clock, this field should
be LOCL. The next field is the stratum of the clock. Actually, it is
really the stratum that is placed in the packet if this clock is selected
by the local NTP daemon as the reference clock. Following that is the
precision which is inserted into the packet when this clock is selected.
The final field is the type of the clock. Currently, two types are
supported: psti for the Precision Standard Time, Inc. WWV clock (a radio
service from the National Institute of Standards and Technology), and
local for the local time of the system. The local clock type can be used
to declare one host on an isolated network as having the ``correct'' time
and then the other hosts on that network can be synchronized to it.
EXAMPLES
2 Intergraph Corporation - 2/94
ntp.conf(4) CLIX ntp.conf(4)
Following is a sample configuration file:
#
# Local clock information
#
# Precision of the local clock to the nearest power of 2
# For example:
# 60-Hz = 2**-6
# 100-Hz = 2**-7
# 1000-Hz = 2**-10
precision -6
#
#
# Time server specifications
#
peer foo
peer 192.5.39.94
peer bar
server bogon
passive bozo
#
# Reference clock
#
# Format: peer device refid stratum precision type
#
peer /dev/tty03 WWV 1 -5 psti
# peer /dev/null LOCL 1 -6 local
FILES
/etc/ntp.conf
Default location for the NTP configuration file.
RELATED INFORMATION
Commands: ntpd(8)
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