NAME

     ntpd.conf — Network Time Protocol daemon configuration file

DESCRIPTION

     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:

                   listen on *

             or

                   listen on 127.0.0.1
                   listen on ::1
                   listen on 127.0.0.1 rtable 4

     query from address
             Specify a local IP address the ntpd(8) daemon should use for outgoing queries to
             subsequently specified servers.  For example:

                   query from 192.0.2.1
                   query from 2001:db8::1

     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:

                   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

             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:

                   sensor nmea0 refid GPS

             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:

                   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.

     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:

                   servers pool.ntp.org
                   servers pool.ntp.org weight 5

CONSTRAINTS

     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.

FILES

     /etc/openntpd/ntpd.conf     default ntpd(8) configuration file
     /etc/default/openntpd       openntpd daemon defaults

SEE ALSO

     ntpctl(8), ntpd(8), sysctl(8)

HISTORY

     The ntpd.conf file format first appeared in OpenBSD 3.6.