ntpd.conf —
Network Time Protocol daemon configuration
file
This manual page describes the format of the
ntpd(8) configuration file.
ntpd.conf has the following format:
Empty lines and lines beginning with the ‘#’ character are
ignored.
Keywords may be specified multiple times within the configuration file. The
basic configuration options are as follows:
-
listen
on address
[rtable
table-id]
-
ntpd(8) has the ability to
sync the local clock to remote NTP servers and, if this directive is
specified, can act as NTP server itself, redistributing the local clock.
Specify a local IP address or a hostname the
ntpd(8) daemon should listen on to enable
remote clients synchronization. If it appears multiple times,
ntpd(8) will listen on each given address. If
‘*’ is given as an address,
ntpd(8) will listen on all local addresses
using the specified routing table. ntpd(8)
does not listen on any address by default. The optional
rtable keyword will specify which routing
table to listen on, if the operating system supports rdomains. By default
ntpd(8) will listen using the current routing
table. For example:
or
-
query
from address
- Specify a local IP address the
ntpd(8) daemon should use for outgoing
queries to subsequently specified servers. For example:
-
sensor
device
[correction
microseconds]
[weight
weight-value]
[refid
string]
[stratum
stratum-value]
- Specify a timedelta sensor device
ntpd(8) should use, if the operating system
supports sensors. The sensor can be specified multiple times:
ntpd(8) will use each given sensor that
actually exists. Non-existent sensors are ignored. If ‘*’ is
given as device name, ntpd(8) will use all
timedelta sensors it finds. ntpd(8) does not
use any timedelta sensor by default. For example:
An optional correction in microseconds can be given to compensate for the
sensor's offset. The maximum correction is 127 seconds. For example, if a
DCF77 receiver is lagging 70ms behind actual time:
The optional weight keyword permits finer
control over the relative importance of time sources (servers or sensor
devices). Weights are specified in the range 1 to 10; if no weight is
given, the default is 1. A server with a weight of 5, for example, will
have five times more influence on time offset calculation than a server
with a weight of 1.
An optional reference ID string - up to 4 ASCII characters - can be given to
publish the sensor type to clients. RFC 2030 suggests some common
reference identifiers, but new identifiers "can be contrived as
appropriate." If an ID string is not given,
ntpd(8) will use a generic reference ID. For
example:
A stratum value other than the default of 1 can be assigned using the
stratum keyword.
-
server
address
[weight
weight-value]
- Specify the IP address or the hostname of an NTP server to
synchronize to. If it appears multiple times,
ntpd(8) will try to synchronize to all of the
servers specified. If a hostname resolves to multiple IPv4 and/or IPv6
addresses, ntpd(8) uses the first address. If
it does not get a reply, ntpd(8) retries with
the next address and continues to do so until a working address is found.
For example:
To provide redundancy, it is good practice to configure multiple servers. In
general, best accuracy is obtained by using servers that have a low
network latency.
-
servers
address
[weight
weight-value]
- As with server, specify the IP
address or hostname of an NTP server to synchronize to. If it appears
multiple times, ntpd(8) will try to
synchronize to all of the servers specified. Should the hostname resolve
to multiple IP addresses, ntpd(8) will try to
synchronize to all of them. For example:
ntpd(8) Hardened TLS for ntpd constraints, enabling
server name verification, is currently
not enabled on
Debian due to missing LibreSSL's libtls implementation at this time.
- /etc/openntpd/ntpd.conf
- default ntpd(8) configuration
file
- /etc/default/openntpd
- openntpd daemon defaults
ntpctl(8),
ntpd(8),
sysctl(8)
The
ntpd.conf file format first appeared in
OpenBSD 3.6.