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.