ntp.conf(5) - phpMan

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ntp.conf(5)                                                        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 configure an  association  with  a
       remote  server, peer or reference clock, and auxilliary commands that specify envi-
       ronmental 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 ref-
       erence 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 preceding
       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 notation. 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 mobilizes a persis-
                       tent client mode association with the specified  remote  server  or
                       local reference clock. If the preempt flag is specified, a preempt-
                       able 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 mobilizes a per-
                       sistent broadcast or multicast server mode association.  Note  that
                       type b messages go only to the interface specified, but type m mes-
                       sages 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  command 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 dis-
                       covery scheme described on the  Association  Management  page.  The
                       address  is a DNS name in the form area.pool.ntp.org, where area is
                       a qualifier designating the server geographic area such  as  us  or
                       europe.

               unpeer  This  command  removes  a  previously  configured  association.  An
                       address or association ID can be used to identify the  association.
                       Either  an IP address or DNS name can be used. This command is most
                       useful when supplied via ntpq runtime configuration commands  :con-
                       fig 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 com-
               mand  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
               recommended 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  mes-
               sages,  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 algorithm but visi-
               ble  to  the  monitoring program. This option is ignored with the broadcast
               command.

       preempt Specifies the association as preemptable rather than  the  default  persis-
               tent.  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 precision 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 packets. 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 broadcast 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  executed.  Note:  the
               novolley  option has been deprecated for future enhancements. Note that, in
               order to avoid accidental or malicious disruption in this  mode,  both  the
               server  and client should operate using symmetric key or public key authen-
               tication as described in the Authentication Options  page.  Note  that  the
               novolley keyword is incompatible with public key authentication.

       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 symmetric 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 hilari-
       ous 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.




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