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1<html lang="en"> 2<head> 3<title>ntpd: Network Time Protocol (NTP) Daemon User's Manual</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="ntpd: Network Time Protocol (NTP) Daemon User's Manual"> 6<meta name="generator" content="makeinfo 4.7"> 7<link title="Top" rel="top" href="#Top"> 8<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 9<meta http-equiv="Content-Style-Type" content="text/css"> 10<style type="text/css"><!-- 11 pre.display { font-family:inherit } 12 pre.format { font-family:inherit } 13 pre.smalldisplay { font-family:inherit; font-size:smaller } 14 pre.smallformat { font-family:inherit; font-size:smaller } 15 pre.smallexample { font-size:smaller } 16 pre.smalllisp { font-size:smaller } 17 span.sc { font-variant:small-caps } 18 span.roman { font-family: serif; font-weight: normal; } 19--></style> 20</head> 21<body> 22<h1 class="settitle">ntpd: Network Time Protocol (NTP) Daemon User's Manual</h1> 23<div class="node"> 24<p><hr> 25<a name="Top"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Description">ntpd Description</a>, 26Previous: <a rel="previous" accesskey="p" href="#dir">(dir)</a>, 27Up: <a rel="up" accesskey="u" href="#dir">(dir)</a> 28<br> 29</div> 30 31<h2 class="unnumbered">ntpd: Network Time Protocol (NTP) Daemon User Manual</h2> 32 33<p>The <code>ntpd</code> program is an operating system daemon that synchronizes the 34system clock to remote NTP time servers or local reference clocks. 35It is a complete implementation of NTP version 4 defined by RFC-5905, but 36also retains compatible with version 3 defined by RFC-1305 and versions 371 and 2, defined by RFC-1059 and RFC-1119, respectively. 38The program can operate in any of several modes, including client/server, 39symmetric and broadcast modes, and with both symmetric-key and public-key 40cryptography. 41 42 <p>This document applies to version 4.2.7p404 of <code>ntpd</code>. 43 44<ul class="menu"> 45<li><a accesskey="1" href="#ntpd-Description">ntpd Description</a>: Description 46<li><a accesskey="2" href="#ntpd-Invocation">ntpd Invocation</a>: Invoking ntpd 47<li><a accesskey="3" href="#Usage">Usage</a>: Usage 48</ul> 49 50<div class="node"> 51<p><hr> 52<a name="ntpd-Description"></a> 53<br> 54</div> 55 56<!-- node-name, next, previous, up --> 57<h3 class="section">Description</h3> 58 59<p>The <code>ntpd</code> program ordinarily requires 60a configuration file described at <a href="#ntp_002econf">ntp.conf</a>. 61This configuration file contains configuration commands described on 62the pages listed above. 63However a client can discover remote servers and configure them 64automatically. 65This makes it possible to deploy a fleet of workstations without 66specifying configuration details specific to the local environment. 67 68 <p>The <code>ntpd</code> program normally operates continuously while adjusting the 69system time and frequency, but in some cases this might not be 70practical. 71With the <code>-q</code> option <code>ntpd</code> operates as in continuous mode, but 72exits just after setting the clock for the first time. 73Most applications will probably want to specify the <code>iburst</code> 74option with the <code>server</code> command. 75With this option an initial volley of messages is exchanged to 76groom the data and set the clock in about ten seconds' time. 77If nothing is heard after a few minutes' time, 78the daemon times out and exits without setting the clock. 79 80<div class="node"> 81<p><hr> 82<a name="ntpd-Invocation"></a> 83<br> 84</div> 85 86<h3 class="section">Invoking ntpd</h3> 87 88<p><a name="index-ntpd-1"></a><a name="index-NTP-daemon-program-2"></a> 89 90 <p>The 91<code>ntpd</code> 92utility is an operating system daemon which sets 93and maintains the system time of day in synchronism with Internet 94standard time servers. 95It is a complete implementation of the 96Network Time Protocol (NTP) version 4, as defined by RFC-5905, 97but also retains compatibility with 98version 3, as defined by RFC-1305, and versions 1 99and 2, as defined by RFC-1059 and RFC-1119, respectively. 100 101 <p>The 102<code>ntpd</code> 103utility does most computations in 64-bit floating point 104arithmetic and does relatively clumsy 64-bit fixed point operations 105only when necessary to preserve the ultimate precision, about 232 106picoseconds. 107While the ultimate precision is not achievable with 108ordinary workstations and networks of today, it may be required 109with future gigahertz CPU clocks and gigabit LANs. 110 111 <p>Ordinarily, 112<code>ntpd</code> 113reads the 114<code>ntp.conf(5)</code> 115configuration file at startup time in order to determine the 116synchronization sources and operating modes. 117It is also possible to 118specify a working, although limited, configuration entirely on the 119command line, obviating the need for a configuration file. 120This may 121be particularly useful when the local host is to be configured as a 122broadcast/multicast client, with all peers being determined by 123listening to broadcasts at run time. 124 125 <p>If NetInfo support is built into 126<code>ntpd</code> 127then 128<code>ntpd</code> 129will attempt to read its configuration from the 130NetInfo if the default 131<code>ntp.conf(5)</code> 132file cannot be read and no file is 133specified by the 134<code>-c</code> 135option. 136 137 <p>Various internal 138<code>ntpd</code> 139variables can be displayed and 140configuration options altered while the 141<code>ntpd</code> 142is running 143using the 144<code>ntpq(1ntpqmdoc)</code> 145and 146<code>ntpdc(1ntpdcmdoc)</code> 147utility programs. 148 149 <p>When 150<code>ntpd</code> 151starts it looks at the value of 152<code>umask(2)</code>, 153and if zero 154<code>ntpd</code> 155will set the 156<code>umask(2)</code> 157to 022. 158 159 <p>This section was generated by <strong>AutoGen</strong>, 160using the <code>agtexi-cmd</code> template and the option descriptions for the <code>ntpd</code> program. 161This software is released under the NTP license, <http://ntp.org/license>. 162 163<ul class="menu"> 164<li><a accesskey="1" href="#ntpd-usage">ntpd usage</a>: ntpd help/usage (<span class="option">--help</span>) 165<li><a accesskey="2" href="#ntpd-ipv4">ntpd ipv4</a>: ipv4 option (-4) 166<li><a accesskey="3" href="#ntpd-ipv6">ntpd ipv6</a>: ipv6 option (-6) 167<li><a accesskey="4" href="#ntpd-authreq">ntpd authreq</a>: authreq option (-a) 168<li><a accesskey="5" href="#ntpd-authnoreq">ntpd authnoreq</a>: authnoreq option (-A) 169<li><a accesskey="6" href="#ntpd-configfile">ntpd configfile</a>: configfile option (-c) 170<li><a accesskey="7" href="#ntpd-driftfile">ntpd driftfile</a>: driftfile option (-f) 171<li><a accesskey="8" href="#ntpd-panicgate">ntpd panicgate</a>: panicgate option (-g) 172<li><a accesskey="9" href="#ntpd-jaildir">ntpd jaildir</a>: jaildir option (-i) 173<li><a href="#ntpd-interface">ntpd interface</a>: interface option (-I) 174<li><a href="#ntpd-keyfile">ntpd keyfile</a>: keyfile option (-k) 175<li><a href="#ntpd-logfile">ntpd logfile</a>: logfile option (-l) 176<li><a href="#ntpd-novirtualips">ntpd novirtualips</a>: novirtualips option (-L) 177<li><a href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>: modifymmtimer option (-M) 178<li><a href="#ntpd-nice">ntpd nice</a>: nice option (-N) 179<li><a href="#ntpd-pidfile">ntpd pidfile</a>: pidfile option (-p) 180<li><a href="#ntpd-priority">ntpd priority</a>: priority option (-P) 181<li><a href="#ntpd-quit">ntpd quit</a>: quit option (-q) 182<li><a href="#ntpd-propagationdelay">ntpd propagationdelay</a>: propagationdelay option (-r) 183<li><a href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>: saveconfigquit option 184<li><a href="#ntpd-statsdir">ntpd statsdir</a>: statsdir option (-s) 185<li><a href="#ntpd-trustedkey">ntpd trustedkey</a>: trustedkey option (-t) 186<li><a href="#ntpd-user">ntpd user</a>: user option (-u) 187<li><a href="#ntpd-updateinterval">ntpd updateinterval</a>: updateinterval option (-U) 188<li><a href="#ntpd-wait_002dsync">ntpd wait-sync</a>: wait-sync option (-w) 189<li><a href="#ntpd-slew">ntpd slew</a>: slew option (-x) 190<li><a href="#ntpd-usepcc">ntpd usepcc</a>: usepcc option 191<li><a href="#ntpd-pccfreq">ntpd pccfreq</a>: pccfreq option 192<li><a href="#ntpd-mdns">ntpd mdns</a>: mdns option (-m) 193<li><a href="#ntpd-config">ntpd config</a>: presetting/configuring ntpd 194<li><a href="#ntpd-exit-status">ntpd exit status</a>: exit status 195<li><a href="#ntpd-Usage">ntpd Usage</a>: Usage 196<li><a href="#ntpd-Files">ntpd Files</a>: Files 197<li><a href="#ntpd-See-Also">ntpd See Also</a>: See Also 198<li><a href="#ntpd-Bugs">ntpd Bugs</a>: Bugs 199<li><a href="#ntpd-Notes">ntpd Notes</a>: Notes 200</ul> 201 202<div class="node"> 203<p><hr> 204<a name="ntpd-usage"></a>Next: <a rel="next" accesskey="n" href="#ntpd-ipv4">ntpd ipv4</a>, 205Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 206<br> 207</div> 208 209<h4 class="subsection">ntpd help/usage (<span class="option">--help</span>)</h4> 210 211<p><a name="index-ntpd-help-3"></a> 212This is the automatically generated usage text for ntpd. 213 214 <p>The text printed is the same whether selected with the <code>help</code> option 215(<span class="option">--help</span>) or the <code>more-help</code> option (<span class="option">--more-help</span>). <code>more-help</code> will print 216the usage text by passing it through a pager program. 217<code>more-help</code> is disabled on platforms without a working 218<code>fork(2)</code> function. The <code>PAGER</code> environment variable is 219used to select the program, defaulting to <span class="file">more</span>. Both will exit 220with a status code of 0. 221 222<pre class="example">ntpd - NTP daemon program - Ver. 4.2.7p403 223Usage: ntpd [ -<flag> [<val>] | --<name>[{=| }<val>] ]... \ 224 [ <server1> ... <serverN> ] 225 Flg Arg Option-Name Description 226 -4 no ipv4 Force IPv4 DNS name resolution 227 - prohibits the option 'ipv6' 228 -6 no ipv6 Force IPv6 DNS name resolution 229 - prohibits the option 'ipv4' 230 -a no authreq Require crypto authentication 231 - prohibits the option 'authnoreq' 232 -A no authnoreq Do not require crypto authentication 233 - prohibits the option 'authreq' 234 -b no bcastsync Allow us to sync to broadcast servers 235 -c Str configfile configuration file name 236 -d no debug-level Increase debug verbosity level 237 - may appear multiple times 238 -D Num set-debug-level Set the debug verbosity level 239 - may appear multiple times 240 -f Str driftfile frequency drift file name 241 -g no panicgate Allow the first adjustment to be Big 242 - may appear multiple times 243 -i Str jaildir Jail directory 244 -I Str interface Listen on an interface name or address 245 - may appear multiple times 246 -k Str keyfile path to symmetric keys 247 -l Str logfile path to the log file 248 -L no novirtualips Do not listen to virtual interfaces 249 -n no nofork Do not fork 250 - prohibits the option 'wait-sync' 251 -N no nice Run at high priority 252 -p Str pidfile path to the PID file 253 -P Num priority Process priority 254 -q no quit Set the time and quit 255 - prohibits these options: 256 saveconfigquit 257 wait-sync 258 -r Str propagationdelay Broadcast/propagation delay 259 Str saveconfigquit Save parsed configuration and quit 260 - prohibits these options: 261 quit 262 wait-sync 263 -s Str statsdir Statistics file location 264 -t Str trustedkey Trusted key number 265 - may appear multiple times 266 -u Str user Run as userid (or userid:groupid) 267 -U Num updateinterval interval in seconds between scans for new or dropped interfaces 268 Str var make ARG an ntp variable (RW) 269 - may appear multiple times 270 Str dvar make ARG an ntp variable (RW|DEF) 271 - may appear multiple times 272 -w Num wait-sync Seconds to wait for first clock sync 273 - prohibits these options: 274 nofork 275 quit 276 saveconfigquit 277 -x no slew Slew up to 600 seconds 278 opt version output version information and exit 279 -? no help display extended usage information and exit 280 -! no more-help extended usage information passed thru pager 281 282Options are specified by doubled hyphens and their name or by a single 283hyphen and the flag character. 284 285 286The following option preset mechanisms are supported: 287 - examining environment variables named NTPD_* 288 289Please send bug reports to: <http://bugs.ntp.org, bugs@ntp.org> 290 291exit 0 292</pre> 293 <div class="node"> 294<p><hr> 295<a name="ntpd-ipv4"></a>Next: <a rel="next" accesskey="n" href="#ntpd-ipv6">ntpd ipv6</a>, 296Previous: <a rel="previous" accesskey="p" href="#ntpd-usage">ntpd usage</a>, 297Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 298<br> 299</div> 300 301<h4 class="subsection">ipv4 option (-4)</h4> 302 303<p><a name="index-ntpd_002dipv4-4"></a> 304This is the “force ipv4 dns name resolution” option. 305 306<p class="noindent">This option has some usage constraints. It: 307 <ul> 308<li>must not appear in combination with any of the following options: 309ipv6. 310</ul> 311 312 <p>Force DNS resolution of following host names on the command line 313to the IPv4 namespace. 314<div class="node"> 315<p><hr> 316<a name="ntpd-ipv6"></a>Next: <a rel="next" accesskey="n" href="#ntpd-authreq">ntpd authreq</a>, 317Previous: <a rel="previous" accesskey="p" href="#ntpd-ipv4">ntpd ipv4</a>, 318Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 319<br> 320</div> 321 322<h4 class="subsection">ipv6 option (-6)</h4> 323 324<p><a name="index-ntpd_002dipv6-5"></a> 325This is the “force ipv6 dns name resolution” option. 326 327<p class="noindent">This option has some usage constraints. It: 328 <ul> 329<li>must not appear in combination with any of the following options: 330ipv4. 331</ul> 332 333 <p>Force DNS resolution of following host names on the command line 334to the IPv6 namespace. 335<div class="node"> 336<p><hr> 337<a name="ntpd-authreq"></a>Next: <a rel="next" accesskey="n" href="#ntpd-authnoreq">ntpd authnoreq</a>, 338Previous: <a rel="previous" accesskey="p" href="#ntpd-ipv6">ntpd ipv6</a>, 339Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 340<br> 341</div> 342 343<h4 class="subsection">authreq option (-a)</h4> 344 345<p><a name="index-ntpd_002dauthreq-6"></a> 346This is the “require crypto authentication” option. 347 348<p class="noindent">This option has some usage constraints. It: 349 <ul> 350<li>must not appear in combination with any of the following options: 351authnoreq. 352</ul> 353 354 <p>Require cryptographic authentication for broadcast client, 355multicast client and symmetric passive associations. 356This is the default. 357<div class="node"> 358<p><hr> 359<a name="ntpd-authnoreq"></a>Next: <a rel="next" accesskey="n" href="#ntpd-configfile">ntpd configfile</a>, 360Previous: <a rel="previous" accesskey="p" href="#ntpd-authreq">ntpd authreq</a>, 361Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 362<br> 363</div> 364 365<h4 class="subsection">authnoreq option (-A)</h4> 366 367<p><a name="index-ntpd_002dauthnoreq-7"></a> 368This is the “do not require crypto authentication” option. 369 370<p class="noindent">This option has some usage constraints. It: 371 <ul> 372<li>must not appear in combination with any of the following options: 373authreq. 374</ul> 375 376 <p>Do not require cryptographic authentication for broadcast client, 377multicast client and symmetric passive associations. 378This is almost never a good idea. 379<div class="node"> 380<p><hr> 381<a name="ntpd-configfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-driftfile">ntpd driftfile</a>, 382Previous: <a rel="previous" accesskey="p" href="#ntpd-authnoreq">ntpd authnoreq</a>, 383Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 384<br> 385</div> 386 387<h4 class="subsection">configfile option (-c)</h4> 388 389<p><a name="index-ntpd_002dconfigfile-8"></a> 390This is the “configuration file name” option. 391This option takes a string argument. 392The name and path of the configuration file, 393<span class="file">/etc/ntp.conf</span> 394by default. 395<div class="node"> 396<p><hr> 397<a name="ntpd-driftfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-panicgate">ntpd panicgate</a>, 398Previous: <a rel="previous" accesskey="p" href="#ntpd-configfile">ntpd configfile</a>, 399Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 400<br> 401</div> 402 403<h4 class="subsection">driftfile option (-f)</h4> 404 405<p><a name="index-ntpd_002ddriftfile-9"></a> 406This is the “frequency drift file name” option. 407This option takes a string argument. 408The name and path of the frequency file, 409<span class="file">/etc/ntp.drift</span> 410by default. 411This is the same operation as the 412<code>driftfile</code> <kbd>driftfile</kbd> 413configuration specification in the 414<span class="file">/etc/ntp.conf</span> 415file. 416<div class="node"> 417<p><hr> 418<a name="ntpd-panicgate"></a>Next: <a rel="next" accesskey="n" href="#ntpd-jaildir">ntpd jaildir</a>, 419Previous: <a rel="previous" accesskey="p" href="#ntpd-driftfile">ntpd driftfile</a>, 420Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 421<br> 422</div> 423 424<h4 class="subsection">panicgate option (-g)</h4> 425 426<p><a name="index-ntpd_002dpanicgate-10"></a> 427This is the “allow the first adjustment to be big” option. 428 429<p class="noindent">This option has some usage constraints. It: 430 <ul> 431<li>may appear an unlimited number of times. 432</ul> 433 434 <p>Normally, 435<code>ntpd</code> 436exits with a message to the system log if the offset exceeds the panic threshold, which is 1000 s by default. This option allows the time to be set to any value without restriction; however, this can happen only once. If the threshold is exceeded after that, 437<code>ntpd</code> 438will exit with a message to the system log. This option can be used with the 439<code>-q</code> 440and 441<code>-x</code> 442options. 443See the 444<code>tinker</code> 445configuration file directive for other options. 446<div class="node"> 447<p><hr> 448<a name="ntpd-jaildir"></a>Next: <a rel="next" accesskey="n" href="#ntpd-interface">ntpd interface</a>, 449Previous: <a rel="previous" accesskey="p" href="#ntpd-panicgate">ntpd panicgate</a>, 450Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 451<br> 452</div> 453 454<h4 class="subsection">jaildir option (-i)</h4> 455 456<p><a name="index-ntpd_002djaildir-11"></a> 457This is the “jail directory” option. 458This option takes a string argument. 459 460<p class="noindent">This option has some usage constraints. It: 461 <ul> 462<li>must be compiled in by defining <code>HAVE_DROPROOT</code> during the compilation. 463</ul> 464 465 <p>Chroot the server to the directory 466<kbd>jaildir</kbd> 467. 468This option also implies that the server attempts to drop root privileges at startup. 469You may need to also specify a 470<code>-u</code> 471option. 472This option is only available if the OS supports adjusting the clock 473without full root privileges. 474This option is supported under NetBSD (configure with 475<code>--enable-clockctl</code>) or Linux (configure with 476<code>--enable-linuxcaps</code>) or Solaris (configure with <code>--enable-solarisprivs</code>). 477<div class="node"> 478<p><hr> 479<a name="ntpd-interface"></a>Next: <a rel="next" accesskey="n" href="#ntpd-keyfile">ntpd keyfile</a>, 480Previous: <a rel="previous" accesskey="p" href="#ntpd-jaildir">ntpd jaildir</a>, 481Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 482<br> 483</div> 484 485<h4 class="subsection">interface option (-I)</h4> 486 487<p><a name="index-ntpd_002dinterface-12"></a> 488This is the “listen on an interface name or address” option. 489This option takes a string argument <span class="file">iface</span>. 490 491<p class="noindent">This option has some usage constraints. It: 492 <ul> 493<li>may appear an unlimited number of times. 494</ul> 495 496 <p>Open the network address given, or all the addresses associated with the 497given interface name. This option may appear multiple times. This option 498also implies not opening other addresses, except wildcard and localhost. 499This option is deprecated. Please consider using the configuration file 500<code>interface</code> command, which is more versatile. 501<div class="node"> 502<p><hr> 503<a name="ntpd-keyfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-logfile">ntpd logfile</a>, 504Previous: <a rel="previous" accesskey="p" href="#ntpd-interface">ntpd interface</a>, 505Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 506<br> 507</div> 508 509<h4 class="subsection">keyfile option (-k)</h4> 510 511<p><a name="index-ntpd_002dkeyfile-13"></a> 512This is the “path to symmetric keys” option. 513This option takes a string argument. 514Specify the name and path of the symmetric key file. 515<span class="file">/etc/ntp.keys</span> 516is the default. 517This is the same operation as the 518<code>keys</code> <kbd>keyfile</kbd> 519configuration file directive. 520<div class="node"> 521<p><hr> 522<a name="ntpd-logfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-novirtualips">ntpd novirtualips</a>, 523Previous: <a rel="previous" accesskey="p" href="#ntpd-keyfile">ntpd keyfile</a>, 524Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 525<br> 526</div> 527 528<h4 class="subsection">logfile option (-l)</h4> 529 530<p><a name="index-ntpd_002dlogfile-14"></a> 531This is the “path to the log file” option. 532This option takes a string argument. 533Specify the name and path of the log file. 534The default is the system log file. 535This is the same operation as the 536<code>logfile</code> <kbd>logfile</kbd> 537configuration file directive. 538<div class="node"> 539<p><hr> 540<a name="ntpd-novirtualips"></a>Next: <a rel="next" accesskey="n" href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>, 541Previous: <a rel="previous" accesskey="p" href="#ntpd-logfile">ntpd logfile</a>, 542Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 543<br> 544</div> 545 546<h4 class="subsection">novirtualips option (-L)</h4> 547 548<p><a name="index-ntpd_002dnovirtualips-15"></a> 549This is the “do not listen to virtual interfaces” option. 550Do not listen to virtual interfaces, defined as those with 551names containing a colon. This option is deprecated. Please 552consider using the configuration file <code>interface</code> command, which 553is more versatile. 554<div class="node"> 555<p><hr> 556<a name="ntpd-modifymmtimer"></a>Next: <a rel="next" accesskey="n" href="#ntpd-nice">ntpd nice</a>, 557Previous: <a rel="previous" accesskey="p" href="#ntpd-novirtualips">ntpd novirtualips</a>, 558Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 559<br> 560</div> 561 562<h4 class="subsection">modifymmtimer option (-M)</h4> 563 564<p><a name="index-ntpd_002dmodifymmtimer-16"></a> 565This is the “modify multimedia timer (windows only)” option. 566 567<p class="noindent">This option has some usage constraints. It: 568 <ul> 569<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 570</ul> 571 572 <p>Set the Windows Multimedia Timer to highest resolution. This 573ensures the resolution does not change while ntpd is running, 574avoiding timekeeping glitches associated with changes. 575<div class="node"> 576<p><hr> 577<a name="ntpd-nice"></a>Next: <a rel="next" accesskey="n" href="#ntpd-pidfile">ntpd pidfile</a>, 578Previous: <a rel="previous" accesskey="p" href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>, 579Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 580<br> 581</div> 582 583<h4 class="subsection">nice option (-N)</h4> 584 585<p><a name="index-ntpd_002dnice-17"></a> 586This is the “run at high priority” option. 587To the extent permitted by the operating system, run 588<code>ntpd</code> 589at the highest priority. 590<div class="node"> 591<p><hr> 592<a name="ntpd-pidfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-priority">ntpd priority</a>, 593Previous: <a rel="previous" accesskey="p" href="#ntpd-nice">ntpd nice</a>, 594Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 595<br> 596</div> 597 598<h4 class="subsection">pidfile option (-p)</h4> 599 600<p><a name="index-ntpd_002dpidfile-18"></a> 601This is the “path to the pid file” option. 602This option takes a string argument. 603Specify the name and path of the file used to record 604<code>ntpd</code>'s 605process ID. 606This is the same operation as the 607<code>pidfile</code> <kbd>pidfile</kbd> 608configuration file directive. 609<div class="node"> 610<p><hr> 611<a name="ntpd-priority"></a>Next: <a rel="next" accesskey="n" href="#ntpd-quit">ntpd quit</a>, 612Previous: <a rel="previous" accesskey="p" href="#ntpd-pidfile">ntpd pidfile</a>, 613Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 614<br> 615</div> 616 617<h4 class="subsection">priority option (-P)</h4> 618 619<p><a name="index-ntpd_002dpriority-19"></a> 620This is the “process priority” option. 621This option takes a number argument. 622To the extent permitted by the operating system, run 623<code>ntpd</code> 624at the specified 625<code>sched_setscheduler(SCHED_FIFO)</code> 626priority. 627<div class="node"> 628<p><hr> 629<a name="ntpd-quit"></a>Next: <a rel="next" accesskey="n" href="#ntpd-propagationdelay">ntpd propagationdelay</a>, 630Previous: <a rel="previous" accesskey="p" href="#ntpd-priority">ntpd priority</a>, 631Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 632<br> 633</div> 634 635<h4 class="subsection">quit option (-q)</h4> 636 637<p><a name="index-ntpd_002dquit-20"></a> 638This is the “set the time and quit” option. 639 640<p class="noindent">This option has some usage constraints. It: 641 <ul> 642<li>must not appear in combination with any of the following options: 643saveconfigquit, wait-sync. 644</ul> 645 646 <p><code>ntpd</code> 647will not daemonize and will exit after the clock is first 648synchronized. This behavior mimics that of the 649<code>ntpdate</code> 650program, which will soon be replaced with a shell script. 651The 652<code>-g</code> 653and 654<code>-x</code> 655options can be used with this option. 656Note: The kernel time discipline is disabled with this option. 657<div class="node"> 658<p><hr> 659<a name="ntpd-propagationdelay"></a>Next: <a rel="next" accesskey="n" href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>, 660Previous: <a rel="previous" accesskey="p" href="#ntpd-quit">ntpd quit</a>, 661Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 662<br> 663</div> 664 665<h4 class="subsection">propagationdelay option (-r)</h4> 666 667<p><a name="index-ntpd_002dpropagationdelay-21"></a> 668This is the “broadcast/propagation delay” option. 669This option takes a string argument. 670Specify the default propagation delay from the broadcast/multicast server to this client. This is necessary only if the delay cannot be computed automatically by the protocol. 671<div class="node"> 672<p><hr> 673<a name="ntpd-saveconfigquit"></a>Next: <a rel="next" accesskey="n" href="#ntpd-statsdir">ntpd statsdir</a>, 674Previous: <a rel="previous" accesskey="p" href="#ntpd-propagationdelay">ntpd propagationdelay</a>, 675Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 676<br> 677</div> 678 679<h4 class="subsection">saveconfigquit option</h4> 680 681<p><a name="index-ntpd_002dsaveconfigquit-22"></a> 682This is the “save parsed configuration and quit” option. 683This option takes a string argument. 684 685<p class="noindent">This option has some usage constraints. It: 686 <ul> 687<li>must be compiled in by defining <code>SAVECONFIG</code> during the compilation. 688<li>must not appear in combination with any of the following options: 689quit, wait-sync. 690</ul> 691 692 <p>Cause <code>ntpd</code> to parse its startup configuration file and save an 693equivalent to the given filename and exit. This option was 694designed for automated testing. 695<div class="node"> 696<p><hr> 697<a name="ntpd-statsdir"></a>Next: <a rel="next" accesskey="n" href="#ntpd-trustedkey">ntpd trustedkey</a>, 698Previous: <a rel="previous" accesskey="p" href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>, 699Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 700<br> 701</div> 702 703<h4 class="subsection">statsdir option (-s)</h4> 704 705<p><a name="index-ntpd_002dstatsdir-23"></a> 706This is the “statistics file location” option. 707This option takes a string argument. 708Specify the directory path for files created by the statistics facility. 709This is the same operation as the 710<code>statsdir</code> <kbd>statsdir</kbd> 711configuration file directive. 712<div class="node"> 713<p><hr> 714<a name="ntpd-trustedkey"></a>Next: <a rel="next" accesskey="n" href="#ntpd-user">ntpd user</a>, 715Previous: <a rel="previous" accesskey="p" href="#ntpd-statsdir">ntpd statsdir</a>, 716Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 717<br> 718</div> 719 720<h4 class="subsection">trustedkey option (-t)</h4> 721 722<p><a name="index-ntpd_002dtrustedkey-24"></a> 723This is the “trusted key number” option. 724This option takes a string argument <span class="file">tkey</span>. 725 726<p class="noindent">This option has some usage constraints. It: 727 <ul> 728<li>may appear an unlimited number of times. 729</ul> 730 731 <p>Add the specified key number to the trusted key list. 732<div class="node"> 733<p><hr> 734<a name="ntpd-user"></a>Next: <a rel="next" accesskey="n" href="#ntpd-updateinterval">ntpd updateinterval</a>, 735Previous: <a rel="previous" accesskey="p" href="#ntpd-trustedkey">ntpd trustedkey</a>, 736Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 737<br> 738</div> 739 740<h4 class="subsection">user option (-u)</h4> 741 742<p><a name="index-ntpd_002duser-25"></a> 743This is the “run as userid (or userid:groupid)” option. 744This option takes a string argument. 745 746<p class="noindent">This option has some usage constraints. It: 747 <ul> 748<li>must be compiled in by defining <code>HAVE_DROPROOT</code> during the compilation. 749</ul> 750 751 <p>Specify a user, and optionally a group, to switch to. 752This option is only available if the OS supports adjusting the clock 753without full root privileges. 754This option is supported under NetBSD (configure with 755<code>--enable-clockctl</code>) or Linux (configure with 756<code>--enable-linuxcaps</code>) or Solaris (configure with <code>--enable-solarisprivs</code>). 757<div class="node"> 758<p><hr> 759<a name="ntpd-updateinterval"></a>Next: <a rel="next" accesskey="n" href="#ntpd-wait_002dsync">ntpd wait-sync</a>, 760Previous: <a rel="previous" accesskey="p" href="#ntpd-user">ntpd user</a>, 761Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 762<br> 763</div> 764 765<h4 class="subsection">updateinterval option (-U)</h4> 766 767<p><a name="index-ntpd_002dupdateinterval-26"></a> 768This is the “interval in seconds between scans for new or dropped interfaces” option. 769This option takes a number argument. 770Give the time in seconds between two scans for new or dropped interfaces. 771For systems with routing socket support the scans will be performed shortly after the interface change 772has been detected by the system. 773Use 0 to disable scanning. 60 seconds is the minimum time between scans. 774<div class="node"> 775<p><hr> 776<a name="ntpd-wait_002dsync"></a>Next: <a rel="next" accesskey="n" href="#ntpd-slew">ntpd slew</a>, 777Previous: <a rel="previous" accesskey="p" href="#ntpd-updateinterval">ntpd updateinterval</a>, 778Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 779<br> 780</div> 781 782<h4 class="subsection">wait-sync option (-w)</h4> 783 784<p><a name="index-ntpd_002dwait_002dsync-27"></a> 785This is the “seconds to wait for first clock sync” option. 786This option takes a number argument. 787 788<p class="noindent">This option has some usage constraints. It: 789 <ul> 790<li>must be compiled in by defining <code>HAVE_WORKING_FORK</code> during the compilation. 791<li>must not appear in combination with any of the following options: 792nofork, quit, saveconfigquit. 793</ul> 794 795 <p>If greater than zero, alters <code>ntpd</code>'s behavior when forking to 796daemonize. Instead of exiting with status 0 immediately after 797the fork, the parent waits up to the specified number of 798seconds for the child to first synchronize the clock. The exit 799status is zero (success) if the clock was synchronized, 800otherwise it is <code>ETIMEDOUT</code>. 801This provides the option for a script starting <code>ntpd</code> to easily 802wait for the first set of the clock before proceeding. 803<div class="node"> 804<p><hr> 805<a name="ntpd-slew"></a>Next: <a rel="next" accesskey="n" href="#ntpd-usepcc">ntpd usepcc</a>, 806Previous: <a rel="previous" accesskey="p" href="#ntpd-wait_002dsync">ntpd wait-sync</a>, 807Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 808<br> 809</div> 810 811<h4 class="subsection">slew option (-x)</h4> 812 813<p><a name="index-ntpd_002dslew-28"></a> 814This is the “slew up to 600 seconds” option. 815Normally, the time is slewed if the offset is less than the step threshold, which is 128 ms by default, and stepped if above the threshold. 816This option sets the threshold to 600 s, which is well within the accuracy window to set the clock manually. 817Note: Since the slew rate of typical Unix kernels is limited to 0.5 ms/s, each second of adjustment requires an amortization interval of 2000 s. 818Thus, an adjustment as much as 600 s will take almost 14 days to complete. 819This option can be used with the 820<code>-g</code> 821and 822<code>-q</code> 823options. 824See the 825<code>tinker</code> 826configuration file directive for other options. 827Note: The kernel time discipline is disabled with this option. 828<div class="node"> 829<p><hr> 830<a name="ntpd-usepcc"></a>Next: <a rel="next" accesskey="n" href="#ntpd-pccfreq">ntpd pccfreq</a>, 831Previous: <a rel="previous" accesskey="p" href="#ntpd-slew">ntpd slew</a>, 832Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 833<br> 834</div> 835 836<h4 class="subsection">usepcc option</h4> 837 838<p><a name="index-ntpd_002dusepcc-29"></a> 839This is the “use cpu cycle counter (windows only)” option. 840 841<p class="noindent">This option has some usage constraints. It: 842 <ul> 843<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 844</ul> 845 846 <p>Attempt to substitute the CPU counter for <code>QueryPerformanceCounter</code>. 847The CPU counter and <code>QueryPerformanceCounter</code> are compared, and if 848they have the same frequency, the CPU counter (RDTSC on x86) is 849used directly, saving the overhead of a system call. 850<div class="node"> 851<p><hr> 852<a name="ntpd-pccfreq"></a>Next: <a rel="next" accesskey="n" href="#ntpd-mdns">ntpd mdns</a>, 853Previous: <a rel="previous" accesskey="p" href="#ntpd-usepcc">ntpd usepcc</a>, 854Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 855<br> 856</div> 857 858<h4 class="subsection">pccfreq option</h4> 859 860<p><a name="index-ntpd_002dpccfreq-30"></a> 861This is the “force cpu cycle counter use (windows only)” option. 862This option takes a string argument. 863 864<p class="noindent">This option has some usage constraints. It: 865 <ul> 866<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 867</ul> 868 869 <p>Force substitution the CPU counter for <code>QueryPerformanceCounter</code>. 870The CPU counter (RDTSC on x86) is used unconditionally with the 871given frequency (in Hz). 872<div class="node"> 873<p><hr> 874<a name="ntpd-mdns"></a>Next: <a rel="next" accesskey="n" href="#ntpd-config">ntpd config</a>, 875Previous: <a rel="previous" accesskey="p" href="#ntpd-pccfreq">ntpd pccfreq</a>, 876Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 877<br> 878</div> 879 880<h4 class="subsection">mdns option (-m)</h4> 881 882<p><a name="index-ntpd_002dmdns-31"></a> 883This is the “register with mdns as a ntp server” option. 884 885<p class="noindent">This option has some usage constraints. It: 886 <ul> 887<li>must be compiled in by defining <code>HAVE_DNSREGISTRATION</code> during the compilation. 888</ul> 889 890 <p>Registers as an NTP server with the local mDNS server which allows 891the server to be discovered via mDNS client lookup. 892 893<div class="node"> 894<p><hr> 895<a name="ntpd-config"></a>Next: <a rel="next" accesskey="n" href="#ntpd-exit-status">ntpd exit status</a>, 896Previous: <a rel="previous" accesskey="p" href="#ntpd-mdns">ntpd mdns</a>, 897Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 898<br> 899</div> 900 901<h4 class="subsection">presetting/configuring ntpd</h4> 902 903<p>Any option that is not marked as <i>not presettable</i> may be preset by 904loading values from environment variables named <code>NTPD</code> and <code>NTPD_<OPTION_NAME></code>. <code><OPTION_NAME></code> must be one of 905the options listed above in upper case and segmented with underscores. 906The <code>NTPD</code> variable will be tokenized and parsed like 907the command line. The remaining variables are tested for existence and their 908values are treated like option arguments. 909 910 <p>The command line options relating to configuration and/or usage help are: 911 912<h5 class="subsubheading">version (-)</h5> 913 914<p>Print the program version to standard out, optionally with licensing 915information, then exit 0. The optional argument specifies how much licensing 916detail to provide. The default is to print just the version. The licensing infomation may be selected with an option argument. 917Only the first letter of the argument is examined: 918 919 <dl> 920<dt><span class="samp">version</span><dd>Only print the version. This is the default. 921<br><dt><span class="samp">copyright</span><dd>Name the copyright usage licensing terms. 922<br><dt><span class="samp">verbose</span><dd>Print the full copyright usage licensing terms. 923</dl> 924 925<div class="node"> 926<p><hr> 927<a name="ntpd-exit-status"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Usage">ntpd Usage</a>, 928Previous: <a rel="previous" accesskey="p" href="#ntpd-config">ntpd config</a>, 929Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 930<br> 931</div> 932 933<h4 class="subsection">ntpd exit status</h4> 934 935<p>One of the following exit values will be returned: 936 <dl> 937<dt><span class="samp">0 (EXIT_SUCCESS)</span><dd>Successful program execution. 938<br><dt><span class="samp">1 (EXIT_FAILURE)</span><dd>The operation failed or the command syntax was not valid. 939</dl> 940 <div class="node"> 941<p><hr> 942<a name="ntpd-Usage"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Files">ntpd Files</a>, 943Previous: <a rel="previous" accesskey="p" href="#ntpd-exit-status">ntpd exit status</a>, 944Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 945<br> 946</div> 947 948<h4 class="subsection">ntpd Usage</h4> 949 950<div class="node"> 951<p><hr> 952<a name="ntpd-Files"></a>Next: <a rel="next" accesskey="n" href="#ntpd-See-Also">ntpd See Also</a>, 953Previous: <a rel="previous" accesskey="p" href="#ntpd-Usage">ntpd Usage</a>, 954Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 955<br> 956</div> 957 958<h4 class="subsection">ntpd Files</h4> 959 960<div class="node"> 961<p><hr> 962<a name="ntpd-See-Also"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Bugs">ntpd Bugs</a>, 963Previous: <a rel="previous" accesskey="p" href="#ntpd-Files">ntpd Files</a>, 964Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 965<br> 966</div> 967 968<h4 class="subsection">ntpd See Also</h4> 969 970<div class="node"> 971<p><hr> 972<a name="ntpd-Bugs"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Notes">ntpd Notes</a>, 973Previous: <a rel="previous" accesskey="p" href="#ntpd-See-Also">ntpd See Also</a>, 974Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 975<br> 976</div> 977 978<h4 class="subsection">ntpd Bugs</h4> 979 980<div class="node"> 981<p><hr> 982<a name="ntpd-Notes"></a>Previous: <a rel="previous" accesskey="p" href="#ntpd-Bugs">ntpd Bugs</a>, 983Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 984<br> 985</div> 986 987<h4 class="subsection">ntpd Notes</h4> 988 989<div class="node"> 990<p><hr> 991<a name="Usage"></a> 992<br> 993</div> 994 995<!-- node-name, next, previous, up --> 996<h3 class="section">Usage</h3> 997 998