ntp.conf(images) - phpMan

ntp.conf(5)                   File Formats Manual                  ntp.conf(5)

NAME
       ntp.conf - Server Options

       Following  is  a  description  of  the configuration commands in NTPv4.
       There are two classes of commands, configuration commands that  config-
       ure  an  association with a remote server, peer or reference clock, and
       auxilliary commands that specify environmental variables  that  control
       various related operations.
       The  various  modes  described  on  the Association Management page are
       determined by the command keyword and  the  DNS  name  or  IP  address.
       Addresses  are  classed  by  type  as (s) a remote server or peer (IPv4
       class A, B and C), (b) the IP broadcast address of a  local  interface,
       (m)  a  multicast  address  (IPv4  class  D),  or (r) a reference clock
       address (127.127.x.x). For type m addresses the IANA has  assigned  the
       multicast  group address IPv4 224.0.1.1 and IPv6 ff05::101 (site local)
       exclusively to NTP, but other nonconflicting addresses can be used.
       If the  Basic  Socket  Interface  Extensions  for  IPv6  (RFC-2553)  is
       detected,  support for the IPv6 address family is generated in addition
       to the default IPv4 address family. IPv6 addresses can be identified by
       the  presence of colons ":" in the address field. IPv6 addresses can be
       used almost everywhere where IPv4  addresses  can  be  used,  with  the
       exception  of  reference  clock  addresses, which are always IPv4. Note
       that in contexts where a host name is expected, a -4 qualifier  preced-
       ing  the host name forces DNS resolution to the IPv4 namespace, while a
       -6 qualifier forces DNS resolution to the IPv6 namespace.

CONFIGURATION COMMANDS
       server address [options ...]
       peer address [options ...]
       broadcast address [options ...]
       manycastclient address [options ...]
       pool address [options ...]
       unpeer [address | associd]
               These commands specify the time server name or  address  to  be
               used  and  the  mode  in  which  to operate. The address can be
               either a DNS name or a IPv4 or IPv6 address in  standard  nota-
               tion.  In  general,  multiple commands of each type can be used
               for different server and peer addresses or multicast groups.
               server  For type s and r addresses (only), this  command  mobi-
                       lizes  a  persistent  client  mode association with the
                       specified remote server or local  reference  clock.  If
                       the  preempt  flag  is  specified, a preemptable client
                       mode association is mobilized instead.
               peer    For type s addresses (only), this command  mobilizes  a
                       persistent  symmetric-active  mode association with the
                       specified remote peer.
               broadcast
                       For type b and m addressees (only), this command  mobi-
                       lizes  a  persistent broadcast or multicast server mode
                       association. Note that type b messages go only  to  the
                       interface  specified,  but  type  m  messages go to all
                       interfaces.
               manycastclient
                       For type m addresses (only), this command  mobilizes  a
                       manycast  client  mode  association  for  the multicast
                       group address specified. In this mode the address  must
                       match  the address specified on the manycastserver com-
                       mand of one or more designated manycast servers.
               pool    For type s messages (only)  this  command  mobilizes  a
                       client  mode  association  for servers implementing the
                       pool automatic server discovery scheme described on the
                       Association  Management page. The address is a DNS name
                       in the form area.pool.ntp.org, where area is  a  quali-
                       fier  designating the server geographic area such as us
                       or europe.
               unpeer  This command removes a previously  configured  associa-
                       tion. An address or association ID can be used to iden-
                       tify the association. Either an IP address or DNS  name
                       can  be used. This command is most useful when supplied
                       via ntpq runtime  configuration  commands  :config  and
                       config-from-file.

COMMAND OPTIONS
       autokey Send  and  receive  packets authenticated by the Autokey scheme
               described in the Authentication Options page.  This  option  is
               mutually exclusive with the key option.
       burst   When  the  server  is  reachable, send a burst of eight packets
               instead of the usual one. The packet spacing is normally  2  s;
               however,  the  spacing between the first and second packets can
               be changed with the calldelay command to allow additional  time
               for a modem or ISDN call to complete. This option is valid only
               with the server command and type s addressesa. It is  a  recom-
               mended  option when the maxpoll option is greater than 10 (1024
               s).
       iburst  When the server is unreachable, send a burst of  eight  packets
               instead  of  the usual one. The packet spacing is normally 2 s;
               however, the spacing between the first and second  packets  can
               be  changed with the calldelay command to allow additional time
               for a modem or ISDN call to complete. This option is valid only
               with  the  server  command and type s addresses. It is a recom-
               mended option with this command.
       key key Send and receive packets authenticated  by  the  symmetric  key
               scheme  described  in  the Authentication Options page. The key
               specifies the key identifier  with  values  from  1  to  65534,
               inclusive.  This  option is mutually exclusive with the autokey
               option.
       minpoll minpoll
       maxpoll maxpoll
               These options specify the minimum and  maximum  poll  intervals
               for  NTP  messages,  in  seconds as a power of two. The maximum
               poll interval defaults to 10 (1024 s), but can be increased  by
               the  maxpoll option to an upper limit of 17 (36 h). The minimum
               poll interval defaults to 6 (64 s), but can be decreased by the
               minpoll option to a lower limit of 3 (8 s).
       mode option
               Pass the option to a reference clock driver, where option is an
               integer in the range from 0 to 255, inclusive. This  option  is
               valid only with type r addresses.
       noselect
               Marks  the  server or peer to be ignored by the selection algo-
               rithm but visible to the monitoring  program.  This  option  is
               ignored with the broadcast command.
       preempt Specifies  the  association  as  preemptable  rather  than  the
               default persistent. This option is ignored with  the  broadcast
               command  and  is  most  useful with the manycastclient and pool
               commands.
       prefer  Mark the server as preferred. All  other  things  being  equal,
               this  host  will  be  chosen for synchronization among a set of
               correctly operating hosts. See the  Mitigation  Rules  and  the
               prefer  Keyword  page  for  further information. This option is
               valid only with the server and peer commands.
       true    Mark the association to  assume  truechimer  status;  that  is,
               always  survive  the  selection and clustering algorithms. This
               option can be used with any association, but is most useful for
               reference  clocks with large jitter on the serial port and pre-
               cision pulse-per-second (PPS)  signals.  Caution:  this  option
               defeats  the  algorithms  designed to cast out falsetickers and
               can allow these sources to set the system clock. This option is
               valid only with the server and peer commands.
       ttl ttl This  option  specifies  the time-to-live ttl for the broadcast
               command and the maximum ttl for the expanding ring search  used
               by  the  manycastclient command. Selection of the proper value,
               which defaults to 127, is something of a black art  and  should
               be  coordinated  with the network administrator. This option is
               invalid with type r addresses.
       version version
               Specifies the version number to be used f or outgoing NTP pack-
               ets. Versions 1-4 are the choices, with version 4 the default.
       xleave  Operate  in  interleaved  mode  (symmetric  and broadcast modes
               only). (see NTP Interleaved Modes)

AUXILLIARY COMMANDS
       broadcastclient
               Enable reception of broadcast  server  messages  to  any  local
               interface (type b address). Ordinarily, upon receiving a broad-
               cast message for the first time, the broadcast client  measures
               the   nominal   server   propagation   delay   using   a  brief
               client/server exchange, after which it continues in listen-only
               mode.  If  a  nonzero  value is specified in the broadcastdelay
               command, the value becomes the delay and the volley is not exe-
               cuted. Note: the novolley option has been deprecated for future
               enhancements. Note that, in order to avoid accidental or  mali-
               cious  disruption  in  this  mode,  both  the server and client
               should operate using symmetric key or public key authentication
               as  described in the Authentication Options page. Note that the
               novolley keyword is incompatible with  public  key  authentica-
               tion.
       manycastserver address [...]
               Enable  reception  of  manycast  client messages (type m)to the
               multicast group address(es) (type m) specified.  At  least  one
               address is required. Note that, in order to avoid accidental or
               malicious disruption, both the server and client should operate
               using  symmetric  key or public key authentication as described
               in the Authentication Options page.
       multicastclient address [...]
               Enable reception of multicast server messages to the  multicast
               group  address(es) (type m) specified. Upon receiving a message
               for the first time, the multicast client measures  the  nominal
               server  propagation  delay using a brief client/server exchange
               with the server, then enters  the  broadcast  client  mode,  in
               which  it  synchronizes  to succeeding multicast messages. Note
               that, in order to avoid accidental or malicious  disruption  in
               this mode, both the server and client should operate using sym-
               metric key or public key authentication  as  described  in  the
               Authentication Options page.

BUGS
       The  syntax  checking is not picky; some combinations of ridiculous and
       even hilarious options and modes may not be detected.

SEE ALSO
       ntpd(8), ntp_auth(5), ntp_mon(5), ntp_acc(5), ntp_clock(5), ntp_misc(5)
       The official HTML documentation.
       This file was automatically generated from HTML source.


                                                                   ntp.conf(5)