NTPD.CONF(5)              OpenBSD Programmer's Manual             NTPD.CONF(5)

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.
     They are as follows:

     listen on address
             Specify a local IP address or a hostname the ntpd(8) daemon
             should listen on.  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.  ntpd(8) does not
             listen on any address by default.  For example:

                   listen on *

             or

                   listen on 127.0.0.1
                   listen on ::1

     sensor device [correction microseconds] [weight weight-value] [refid
             string]
             Specify a timedelta sensor device ntpd(8) should use.  The sensor
             can be specified multiple times: ntpd(8) will use each given sen-
             sor that actually exists.  Non-existent sensors are ignored.  If
             `*' is given as device name, ntpd(8) will use all timedelta sen-
             sors it finds.  ntpd(8) does not use any timedelta sensor by de-
             fault.  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 rela-
             tive importance of time sources (servers or sensor devices).
             Weights are specified in the range 1 to 10; if no weight is giv-
             en, 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 sug-
             gests 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

     server address [weight weight-value]
             Specify the IP address or the hostname of an NTP server to syn-
             chronize to.  If it appears multiple times, ntpd(8) will try to
             synchronize to all of the servers specified.  If a hostname re-
             solves 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

FILES
     /etc/ntpd.conf     default ntpd(8) configuration file

SEE ALSO
     ntpd(8), sysctl(8)

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

OpenBSD 4.5                      May 18, 2009                                2