19c2daa00SOllivier Robert<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 29c2daa00SOllivier Robert<html> 39c2daa00SOllivier Robert<head> 4ea906c41SOllivier Robert<meta http-equiv="content-type" content="text/html;charset=iso-8859-1"> 59c2daa00SOllivier Robert<meta name="generator" content="HTML Tidy, see www.w3.org"> 62b15cb3dSCy Schubert<title>Server Commands and Options</title> 72b15cb3dSCy Schubert<!-- Changed by: Harlan &, 31-Jan-2014 --> 89c2daa00SOllivier Robert<link href="scripts/style.css" type="text/css" rel="stylesheet"> 99c2daa00SOllivier Robert</head> 109c2daa00SOllivier Robert<body> 112b15cb3dSCy Schubert<h3>Server Commands and Options</h3> 122b15cb3dSCy Schubert<img src="pic/boom3a.gif" alt="gif" align="left"><a href="http://www.eecis.udel.edu/~mills/pictures.html">from <i>Pogo</i>, 132b15cb3dSCy SchubertWalt Kelly</a> 149c2daa00SOllivier Robert<p>The chicken is getting configuration advice.</p> 152b15cb3dSCy Schubert<p>Last update: 16*2d4e511cSCy Schubert <!-- #BeginDate format:En2m -->13-Feb-2020 10:08<!-- #EndDate --> 172b15cb3dSCy Schubert UTC</p> 189c2daa00SOllivier Robert<br clear="left"> 199c2daa00SOllivier Robert<h4>Related Links</h4> 202b15cb3dSCy Schubert<script type="text/javascript" language="javascript" src="scripts/command.txt"></script> 212b15cb3dSCy Schubert<script type="text/javascript" language="javascript" src="scripts/confopt.txt"></script> 229c2daa00SOllivier Robert<h4>Table of Contents</h4> 239c2daa00SOllivier Robert<ul> 242b15cb3dSCy Schubert <li class="inline"><a href="#address">Server and Peer Addresses</a></li> 252b15cb3dSCy Schubert <li class="inline"><a href="#command">Server Commands</a></li> 262b15cb3dSCy Schubert <li class="inline"><a href="#option">Server Command Options</a></li> 279c2daa00SOllivier Robert</ul> 289c2daa00SOllivier Robert<hr> 292b15cb3dSCy Schubert<h4 id="address">Server and Peer Addresses</h4> 302b15cb3dSCy Schubert<p>Following is a description of the server 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 auxiliary commands that specify environment variables that control various related operations. </p> 312b15cb3dSCy Schubert<p>The various modes described on the <a href="assoc.html">Association Management</a> 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 or IPv6), (b) the IPv4 broadcast address of a local interface, (m) a multicast address (IPv4 class D or IPv6), 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. </p> 322b15cb3dSCy Schubert<p>If the Basic Socket Interface Extensions for IPv6 (RFC-2553) is detected, 332b15cb3dSCy Schubert 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 <tt>-4</tt> qualifier preceding the host name forces DNS resolution to the IPv4 namespace, while a <tt>-6</tt> qualifier forces DNS resolution to the IPv6 namespace.</p> 342b15cb3dSCy Schubert<h4 id="command">Server Commands</h4> 352b15cb3dSCy Schubert<p>Unless noted otherwise, further information about these commands is on the <a href="assoc.html">Association Management</a> page.</p><dl> 36*2d4e511cSCy Schubert <dt id="server"><tt>server <i>address</i> [options ...]</tt></dt> 37*2d4e511cSCy Schubert <dt><tt>peer <i>address</i> [options ...]</tt></dt> 38*2d4e511cSCy Schubert <dt><tt>broadcast <i>address</i> [options ...]</tt></dt> 39*2d4e511cSCy Schubert <dt><tt>manycastclient <i>address</i> [options ...]</tt></dt> 40*2d4e511cSCy Schubert <dt><tt>pool <i>address</i> [options ...]</tt></dt> 41*2d4e511cSCy Schubert <dt><tt>unpeer [<i>address</i> | <i>associd</i>]</tt></dt> 422b15cb3dSCy Schubert <dd>These commands specify the remote server name or address to be used and the mode in which to operate. The <i>address</i> 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. 439c2daa00SOllivier Robert <dl> 442b15cb3dSCy Schubert <dt><tt>server</tt></dt> 452b15cb3dSCy Schubert <dd>For type s and r addresses (only), this command mobilizes a persistent client mode association with the specified remote server or local reference clock. If the <tt>preempt</tt> flag is specified, a preemptable client mode association is mobilized instead.</dd> 462b15cb3dSCy Schubert <dt id="peer"><tt>peer</tt></dt> 472b15cb3dSCy Schubert <dd>For type s addresses (only), this command mobilizes a persistent symmetric-active mode association with the specified remote peer.</dd> 482b15cb3dSCy Schubert <dt id="broadcast"><tt>broadcast</tt></dt> 492b15cb3dSCy Schubert <dd>For type b and m addressees (only), this command mobilizes a 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.</dd> 502b15cb3dSCy Schubert <dt id="manycastclient"><tt>manycastclient</tt></dt> 512b15cb3dSCy Schubert <dd>For type m addresses (only), this command mobilizes a preemptable manycast client mode association for the multicast group address specified. In this mode the address must match the address specified on the <tt>manycastserver</tt> command of one or more designated manycast servers. Additional information about this command is on the <a href="discover.html#mcst">Automatic Server Discovery</a> page.</dd> 522b15cb3dSCy Schubert <dt id="pool"><tt>pool</tt></dt> 532b15cb3dSCy Schubert <dd>For type s addresses (only) this command mobilizes a preemptable pool client mode association for the DNS name specified. The DNS name must resolve to one or more IPv4 or IPv6 addresses. Additional information about this command is on the <a href="discover.html#pool">Automatic Server Discovery</a> page. The <a href="http://www.pool.ntp.org/">www.pool.ntp.org</a> page describes a compatible pool of public NTP servers.</dd> 542b15cb3dSCy Schubert <dt id="unpeer"><tt>unpeer</tt></dt> 552b15cb3dSCy Schubert <dd>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 <tt><a href="ntpq.html">ntpq</a></tt> runtime configuration commands <tt>:config</tt> and <tt>config-from-file</tt>.</dd> 562b15cb3dSCy Schubert </dl></dd> 572b15cb3dSCy Schubert</dl> 582b15cb3dSCy Schubert<h4 id="option">Server Command Options</h4> 599c2daa00SOllivier Robert<dl> 602b15cb3dSCy Schubert <dt><tt>autokey</tt></dt> 612b15cb3dSCy Schubert <dd>Send and receive packets authenticated by the Autokey scheme described 622b15cb3dSCy Schubert on the <a href="autokey.html">Autokey Public Key Authentication</a> page. This option is mutually exclusive with the <tt>key</tt> option.</dd> 632b15cb3dSCy Schubert <dt id="burst"><tt>burst</tt></dt> 642b15cb3dSCy Schubert <dd>When the server is reachable, send a burst of packets instead of the usual one. This option is valid only with the <tt>server</tt> command and type s addresses. It is a recommended option when the <tt>maxpoll</tt> option is greater than 10 (1024 s). Additional information about this option is on the <a href="poll.html">Poll Program</a> page.</dd> 652b15cb3dSCy Schubert <dt><tt>iburst</tt></dt> 662b15cb3dSCy Schubert <dd>When the server is unreachable, send a burst of packets instead of the usual one. This option is valid only with the <tt>server</tt> command and type <tt>s</tt> addresses. It is a recommended option with this command. Additional information about this option is on the <a href="poll.html">Poll Program</a> page.</dd> 672b15cb3dSCy Schubert <dt><tt>ident</tt> <em><tt>group</tt></em></dt> 682b15cb3dSCy Schubert <dd>Specify the group name for the association. See the <a href="autokey.html">Autokey Public-Key Authentication</a> page for further information.</dd> 692b15cb3dSCy Schubert <dt><tt>key</tt> <i><tt>key</tt></i></dt> 70*2d4e511cSCy Schubert <dd>Send and receive packets authenticated by the symmetric key scheme 71*2d4e511cSCy Schubert described in the <a href="authentic.html">Authentication Support</a> 72*2d4e511cSCy Schubert page. The <i><tt>key</tt></i> specifies the key identifier with values 73*2d4e511cSCy Schubert from 1 to 65535, inclusive. This option is mutually exclusive with 74*2d4e511cSCy Schubert the <tt>autokey</tt> 75*2d4e511cSCy Schubert option.</dd> 76*2d4e511cSCy Schubert <dt><tt>minpoll <i>minpoll</i></tt></dt> 77*2d4e511cSCy Schubert <dt><tt>maxpoll <i>maxpoll</i></tt></dt> 782b15cb3dSCy Schubert <dd>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 <tt>maxpoll</tt> option to an upper limit of 17 (36 hr). The minimum poll interval defaults to 6 (64 s), but can be decreased by the <tt>minpoll</tt> option to a lower limit of 3 (8 s). Additional information about this option is on the <a href="poll.html">Poll Program</a> page.</dd> 792b15cb3dSCy Schubert <dt><tt>mode <i>option</i></tt></dt> 802b15cb3dSCy Schubert <dd>Pass the <tt><i>option</i></tt> to a reference clock driver, where <tt><i>option</i></tt> is an integer in the range from 0 to 255, inclusive. This option is valid only with type r addresses.</dd> 812b15cb3dSCy Schubert <dt><tt>noselect</tt></dt> 822b15cb3dSCy Schubert <dd>Marks the server or peer to be ignored by the selection algorithm as unreachable, but visible to the monitoring program. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd> 832b15cb3dSCy Schubert <dt><tt>preempt</tt></dt> 842b15cb3dSCy Schubert <dd>Specifies the association as preemptable rather than the default persistent. This option is ignored with the <tt>broadcast</tt> command and is most useful with the <tt>manycastclient</tt> and <tt>pool</tt> commands.</dd> 852b15cb3dSCy Schubert <dt><tt>prefer</tt></dt> 862b15cb3dSCy Schubert <dd>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 <a href="prefer.html">Mitigation Rules and the <tt>prefer</tt> Keyword</a> page for further information. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd> 872b15cb3dSCy Schubert <dt><tt>true</tt></dt> 882b15cb3dSCy Schubert <dd>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 <tt>server</tt> and <tt>peer</tt> commands.</dd> 892b15cb3dSCy Schubert <dt><tt>ttl <i>ttl</i></tt></dt> 902b15cb3dSCy Schubert <dd>This option specifies the time-to-live <i><tt>ttl</tt></i> for the <tt>broadcast</tt> command and the maximum <i><tt>ttl</tt></i> for the expanding ring search used by the <tt>manycastclient</tt> 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.</dd> 912b15cb3dSCy Schubert <dt><tt>version <i>version</i></tt></dt> 922b15cb3dSCy Schubert <dd>Specifies the version number to be used for 932b15cb3dSCy Schubertoutgoing NTP packets. Versions 1-4 are the choices, with version 4 the default.</dd> 942b15cb3dSCy Schubert <dt><tt>xleave</tt></dt> 952b15cb3dSCy Schubert <dd>Operate in interleaved mode (symmetric and broadcast modes only). Further information is on the <a href="xleave.html">NTP Interleaved Modes</a> page.</dd> 96*2d4e511cSCy Schubert <dt><tt>xmtnonce</tt></dt> 97*2d4e511cSCy Schubert <dd>Allowed in the server and pool modes, this flag causes the 98*2d4e511cSCy Schubert client to put a random number nonce in the transmit timestamp of 99*2d4e511cSCy Schubert its outgoing packet. Since the server will reply copying the 100*2d4e511cSCy Schubert incoming transmit timestamp to the outgoing origin timestamp, this 101*2d4e511cSCy Schubert flag provides extra security for the loopback test, at the expense 102*2d4e511cSCy Schubert of the server having no idea what time the client thinks it is.</dd> 1039c2daa00SOllivier Robert</dl> 1042b15cb3dSCy Schubert<h4 id="aux">Auxiliary Commands</h4> 1059c2daa00SOllivier Robert<dl> 1062b15cb3dSCy Schubert <dt id="broadcastclient"><tt>broadcastclient</tt></dt> 1072b15cb3dSCy Schubert <dd>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 <tt>broadcastdelay</tt> command, the value becomes the delay and the volley is not executed. Note: the <tt>novolley</tt> 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 authentication as described in the <a href="authopt.html">Authentication Options</a> page. Note that the volley is required with public key authentication in order to run the Autokey protocol.</dd> 1082b15cb3dSCy Schubert <dt id="manycastserver"><tt>manycastserver <i>address</i> [...]</tt></dt> 1092b15cb3dSCy Schubert <dd>Enable reception of manycast client messages (type m) to the multicasts 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 <a href="authopt.html">Authentication Options</a> page.</dd> 1102b15cb3dSCy Schubert <dt id="multicastclient"><tt>multicastclient <i>address</i> [...]</tt></dt> 1112b15cb3dSCy Schubert <dd>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 <a href="authopt.html">Authentication Options</a> page.</dd> 1122b15cb3dSCy Schubert <dt id="mdnstries"><tt>mdnstries</tt> <i>number</i></dt> 1132b15cb3dSCy Schubert <dd>If we are participating in mDNS, after we have synched for the first time we attempt to register with the mDNS system. If that registration attempt fails, we try again at one minute intervals for up to <tt>mdnstries</tt> times. After all, <tt>ntpd</tt> may be starting before mDNS. The default value for <tt>mdnstries</tt> is 5.</dd> 1149c2daa00SOllivier Robert</dl> 1159c2daa00SOllivier Robert<hr> 1169c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/footer.txt"></script> 1179c2daa00SOllivier Robert</body> 1189c2daa00SOllivier Robert</html> 119
