|NTPD.CONF(5)||File Formats Manual||NTPD.CONF(5)|
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 onaddress [
- 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
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
rtablekeyword 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:
listen on *
listen on 127.0.0.1 listen on ::1 listen on 127.0.0.1 rtable 4
- Specify a local IP address the
should use for outgoing queries to subsequently specified servers. For
query from 192.0.2.1 query from 2001:db8::1
- Specify a timedelta sensor device
ntpd(8) should use,
if the operating system supports sensors. The sensor can be specified
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:
sensor * sensor nmea0
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:
sensor udcf0 correction 70000
weightkeyword 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:
sensor nmea0 refid GPS
A stratum value other than the default of 1 can be assigned using the
- 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.
server 10.0.0.2 weight 5 server ntp.example.org weight 1
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.
- 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:
servers pool.ntp.org servers pool.ntp.org weight 5
- Specify the URL, IP address or the hostname of an HTTPS server to provide
a constraint. If
constraint fromis used more than once, ntpd(8) will calculate a median constraint from all the servers specified.
server ntp.example.org constraint from www.example.com
- As with
constraint from, specify the URL, IP address or the hostname of an HTTPS server to provide a constraint. Should the hostname resolve to multiple IP addresses, ntpd(8) will calculate a median constraint from all of them. For example:
servers pool.ntp.org constraints from "https://www.google.com/"
- default ntpd(8) configuration file
ntpd.conffile format first appeared in OpenBSD 3.6.
|August 10, 2017||Linux 4.20.11-arch2-1-ARCH|