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.

Debian                                           August 10, 2017                                    NTPD.CONF(5)