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23<h1 class="settitle">ntpd: Network Time Protocol (NTP) Daemon User's Manual</h1> 24<div class="node"> 25<p><hr> 26<a name="Top"></a> 27Next: <a rel="next" accesskey="n" href="#ntpd-Description">ntpd Description</a>, 28Previous: <a rel="previous" accesskey="p" href="#dir">(dir)</a>, 29Up: <a rel="up" accesskey="u" href="#dir">(dir)</a> 30 31</div> 32 33<h2 class="unnumbered">ntpd: Network Time Protocol (NTP) Daemon User Manual</h2> 34 35<p>The <code>ntpd</code> program is an operating system daemon that synchronizes the 36system clock to remote NTP time servers or local reference clocks. 37It is a complete implementation of NTP version 4 defined by RFC-5905, but 38also retains compatible with version 3 defined by RFC-1305 and versions 391 and 2, defined by RFC-1059 and RFC-1119, respectively. 40The program can operate in any of several modes, including client/server, 41symmetric and broadcast modes, and with both symmetric-key and public-key 42cryptography. 43 44 <p>This document applies to version 4.2.8p5 of <code>ntpd</code>. 45 46<ul class="menu"> 47<li><a accesskey="1" href="#ntpd-Description">ntpd Description</a>: Description 48<li><a accesskey="2" href="#ntpd-Invocation">ntpd Invocation</a>: Invoking ntpd 49<li><a accesskey="3" href="#Usage">Usage</a>: Usage 50</ul> 51 52<div class="node"> 53<p><hr> 54<a name="ntpd-Description"></a> 55 56 57</div> 58 59<!-- node-name, next, previous, up --> 60<h3 class="section">Description</h3> 61 62<p>The <code>ntpd</code> program ordinarily requires 63a configuration file described at <a href="#ntp_002econf">ntp.conf</a>. 64This configuration file contains configuration commands described on 65the pages listed above. 66However a client can discover remote servers and configure them 67automatically. 68This makes it possible to deploy a fleet of workstations without 69specifying configuration details specific to the local environment. 70 71 <p>The <code>ntpd</code> program normally operates continuously while adjusting the 72system time and frequency, but in some cases this might not be 73practical. 74With the <code>-q</code> option <code>ntpd</code> operates as in continuous mode, but 75exits just after setting the clock for the first time. 76Most applications will probably want to specify the <code>iburst</code> 77option with the <code>server</code> command. 78With this option an initial volley of messages is exchanged to 79groom the data and set the clock in about ten seconds' time. 80If nothing is heard after a few minutes' time, 81the daemon times out and exits without setting the clock. 82 83<div class="node"> 84<p><hr> 85<a name="ntpd-Invocation"></a> 86 87 88</div> 89 90<h3 class="section">Invoking ntpd</h3> 91 92<p><a name="index-ntpd-1"></a><a name="index-NTP-daemon-program-2"></a> 93 94 <p>The 95<code>ntpd</code> 96utility is an operating system daemon which sets 97and maintains the system time of day in synchronism with Internet 98standard time servers. 99It is a complete implementation of the 100Network Time Protocol (NTP) version 4, as defined by RFC-5905, 101but also retains compatibility with 102version 3, as defined by RFC-1305, and versions 1 103and 2, as defined by RFC-1059 and RFC-1119, respectively. 104 105 <p>The 106<code>ntpd</code> 107utility does most computations in 64-bit floating point 108arithmetic and does relatively clumsy 64-bit fixed point operations 109only when necessary to preserve the ultimate precision, about 232 110picoseconds. 111While the ultimate precision is not achievable with 112ordinary workstations and networks of today, it may be required 113with future gigahertz CPU clocks and gigabit LANs. 114 115 <p>Ordinarily, 116<code>ntpd</code> 117reads the 118<code>ntp.conf(5)</code> 119configuration file at startup time in order to determine the 120synchronization sources and operating modes. 121It is also possible to 122specify a working, although limited, configuration entirely on the 123command line, obviating the need for a configuration file. 124This may 125be particularly useful when the local host is to be configured as a 126broadcast/multicast client, with all peers being determined by 127listening to broadcasts at run time. 128 129 <p>If NetInfo support is built into 130<code>ntpd</code> 131then 132<code>ntpd</code> 133will attempt to read its configuration from the 134NetInfo if the default 135<code>ntp.conf(5)</code> 136file cannot be read and no file is 137specified by the 138<code>-c</code> 139option. 140 141 <p>Various internal 142<code>ntpd</code> 143variables can be displayed and 144configuration options altered while the 145<code>ntpd</code> 146is running 147using the 148<code>ntpq(1ntpqmdoc)</code> 149and 150<code>ntpdc(1ntpdcmdoc)</code> 151utility programs. 152 153 <p>When 154<code>ntpd</code> 155starts it looks at the value of 156<code>umask(2)</code>, 157and if zero 158<code>ntpd</code> 159will set the 160<code>umask(2)</code> 161to 022. 162 163 <p>This section was generated by <strong>AutoGen</strong>, 164using the <code>agtexi-cmd</code> template and the option descriptions for the <code>ntpd</code> program. 165This software is released under the NTP license, <http://ntp.org/license>. 166 167<ul class="menu"> 168<li><a accesskey="1" href="#ntpd-usage">ntpd usage</a>: ntpd help/usage (<samp><span class="option">--help</span></samp>) 169<li><a accesskey="2" href="#ntpd-ipv4">ntpd ipv4</a>: ipv4 option (-4) 170<li><a accesskey="3" href="#ntpd-ipv6">ntpd ipv6</a>: ipv6 option (-6) 171<li><a accesskey="4" href="#ntpd-authreq">ntpd authreq</a>: authreq option (-a) 172<li><a accesskey="5" href="#ntpd-authnoreq">ntpd authnoreq</a>: authnoreq option (-A) 173<li><a accesskey="6" href="#ntpd-configfile">ntpd configfile</a>: configfile option (-c) 174<li><a accesskey="7" href="#ntpd-driftfile">ntpd driftfile</a>: driftfile option (-f) 175<li><a accesskey="8" href="#ntpd-panicgate">ntpd panicgate</a>: panicgate option (-g) 176<li><a accesskey="9" href="#ntpd-force_002dstep_002donce">ntpd force-step-once</a>: force-step-once option (-G) 177<li><a href="#ntpd-jaildir">ntpd jaildir</a>: jaildir option (-i) 178<li><a href="#ntpd-interface">ntpd interface</a>: interface option (-I) 179<li><a href="#ntpd-keyfile">ntpd keyfile</a>: keyfile option (-k) 180<li><a href="#ntpd-logfile">ntpd logfile</a>: logfile option (-l) 181<li><a href="#ntpd-novirtualips">ntpd novirtualips</a>: novirtualips option (-L) 182<li><a href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>: modifymmtimer option (-M) 183<li><a href="#ntpd-nice">ntpd nice</a>: nice option (-N) 184<li><a href="#ntpd-pidfile">ntpd pidfile</a>: pidfile option (-p) 185<li><a href="#ntpd-priority">ntpd priority</a>: priority option (-P) 186<li><a href="#ntpd-quit">ntpd quit</a>: quit option (-q) 187<li><a href="#ntpd-propagationdelay">ntpd propagationdelay</a>: propagationdelay option (-r) 188<li><a href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>: saveconfigquit option 189<li><a href="#ntpd-statsdir">ntpd statsdir</a>: statsdir option (-s) 190<li><a href="#ntpd-trustedkey">ntpd trustedkey</a>: trustedkey option (-t) 191<li><a href="#ntpd-user">ntpd user</a>: user option (-u) 192<li><a href="#ntpd-updateinterval">ntpd updateinterval</a>: updateinterval option (-U) 193<li><a href="#ntpd-wait_002dsync">ntpd wait-sync</a>: wait-sync option (-w) 194<li><a href="#ntpd-slew">ntpd slew</a>: slew option (-x) 195<li><a href="#ntpd-usepcc">ntpd usepcc</a>: usepcc option 196<li><a href="#ntpd-pccfreq">ntpd pccfreq</a>: pccfreq option 197<li><a href="#ntpd-mdns">ntpd mdns</a>: mdns option (-m) 198<li><a href="#ntpd-config">ntpd config</a>: presetting/configuring ntpd 199<li><a href="#ntpd-exit-status">ntpd exit status</a>: exit status 200<li><a href="#ntpd-Usage">ntpd Usage</a>: Usage 201<li><a href="#ntpd-Files">ntpd Files</a>: Files 202<li><a href="#ntpd-See-Also">ntpd See Also</a>: See Also 203<li><a href="#ntpd-Bugs">ntpd Bugs</a>: Bugs 204<li><a href="#ntpd-Notes">ntpd Notes</a>: Notes 205</ul> 206 207<div class="node"> 208<p><hr> 209<a name="ntpd-usage"></a> 210Next: <a rel="next" accesskey="n" href="#ntpd-ipv4">ntpd ipv4</a>, 211Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 212 213</div> 214 215<h4 class="subsection">ntpd help/usage (<samp><span class="option">--help</span></samp>)</h4> 216 217<p><a name="index-ntpd-help-3"></a> 218This is the automatically generated usage text for ntpd. 219 220 <p>The text printed is the same whether selected with the <code>help</code> option 221(<samp><span class="option">--help</span></samp>) or the <code>more-help</code> option (<samp><span class="option">--more-help</span></samp>). <code>more-help</code> will print 222the usage text by passing it through a pager program. 223<code>more-help</code> is disabled on platforms without a working 224<code>fork(2)</code> function. The <code>PAGER</code> environment variable is 225used to select the program, defaulting to <samp><span class="file">more</span></samp>. Both will exit 226with a status code of 0. 227 228<pre class="example">ntpd - NTP daemon program - Ver. 4.2.8p4 229Usage: ntpd [ -<flag> [<val>] | --<name>[{=| }<val>] ]... \ 230 [ <server1> ... <serverN> ] 231 Flg Arg Option-Name Description 232 -4 no ipv4 Force IPv4 DNS name resolution 233 - prohibits the option 'ipv6' 234 -6 no ipv6 Force IPv6 DNS name resolution 235 - prohibits the option 'ipv4' 236 -a no authreq Require crypto authentication 237 - prohibits the option 'authnoreq' 238 -A no authnoreq Do not require crypto authentication 239 - prohibits the option 'authreq' 240 -b no bcastsync Allow us to sync to broadcast servers 241 -c Str configfile configuration file name 242 -d no debug-level Increase debug verbosity level 243 - may appear multiple times 244 -D Num set-debug-level Set the debug verbosity level 245 - may appear multiple times 246 -f Str driftfile frequency drift file name 247 -g no panicgate Allow the first adjustment to be Big 248 - may appear multiple times 249 -G no force-step-once Step any initial offset correction. 250 -i Str jaildir Jail directory 251 -I Str interface Listen on an interface name or address 252 - may appear multiple times 253 -k Str keyfile path to symmetric keys 254 -l Str logfile path to the log file 255 -L no novirtualips Do not listen to virtual interfaces 256 -n no nofork Do not fork 257 - prohibits the option 'wait-sync' 258 -N no nice Run at high priority 259 -p Str pidfile path to the PID file 260 -P Num priority Process priority 261 -q no quit Set the time and quit 262 - prohibits these options: 263 saveconfigquit 264 wait-sync 265 -r Str propagationdelay Broadcast/propagation delay 266 Str saveconfigquit Save parsed configuration and quit 267 - prohibits these options: 268 quit 269 wait-sync 270 -s Str statsdir Statistics file location 271 -t Str trustedkey Trusted key number 272 - may appear multiple times 273 -u Str user Run as userid (or userid:groupid) 274 -U Num updateinterval interval in seconds between scans for new or dropped interfaces 275 Str var make ARG an ntp variable (RW) 276 - may appear multiple times 277 Str dvar make ARG an ntp variable (RW|DEF) 278 - may appear multiple times 279 -w Num wait-sync Seconds to wait for first clock sync 280 - prohibits these options: 281 nofork 282 quit 283 saveconfigquit 284 -x no slew Slew up to 600 seconds 285 opt version output version information and exit 286 -? no help display extended usage information and exit 287 -! no more-help extended usage information passed thru pager 288 289Options are specified by doubled hyphens and their name or by a single 290hyphen and the flag character. 291 292 293The following option preset mechanisms are supported: 294 - examining environment variables named NTPD_* 295 296Please send bug reports to: <http://bugs.ntp.org, bugs@ntp.org> 297</pre> 298 <div class="node"> 299<p><hr> 300<a name="ntpd-ipv4"></a> 301Next: <a rel="next" accesskey="n" href="#ntpd-ipv6">ntpd ipv6</a>, 302Previous: <a rel="previous" accesskey="p" href="#ntpd-usage">ntpd usage</a>, 303Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 304 305</div> 306 307<h4 class="subsection">ipv4 option (-4)</h4> 308 309<p><a name="index-ntpd_002dipv4-4"></a> 310This is the “force ipv4 dns name resolution” option. 311 312<p class="noindent">This option has some usage constraints. It: 313 <ul> 314<li>must not appear in combination with any of the following options: 315ipv6. 316</ul> 317 318 <p>Force DNS resolution of following host names on the command line 319to the IPv4 namespace. 320<div class="node"> 321<p><hr> 322<a name="ntpd-ipv6"></a> 323Next: <a rel="next" accesskey="n" href="#ntpd-authreq">ntpd authreq</a>, 324Previous: <a rel="previous" accesskey="p" href="#ntpd-ipv4">ntpd ipv4</a>, 325Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 326 327</div> 328 329<h4 class="subsection">ipv6 option (-6)</h4> 330 331<p><a name="index-ntpd_002dipv6-5"></a> 332This is the “force ipv6 dns name resolution” option. 333 334<p class="noindent">This option has some usage constraints. It: 335 <ul> 336<li>must not appear in combination with any of the following options: 337ipv4. 338</ul> 339 340 <p>Force DNS resolution of following host names on the command line 341to the IPv6 namespace. 342<div class="node"> 343<p><hr> 344<a name="ntpd-authreq"></a> 345Next: <a rel="next" accesskey="n" href="#ntpd-authnoreq">ntpd authnoreq</a>, 346Previous: <a rel="previous" accesskey="p" href="#ntpd-ipv6">ntpd ipv6</a>, 347Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 348 349</div> 350 351<h4 class="subsection">authreq option (-a)</h4> 352 353<p><a name="index-ntpd_002dauthreq-6"></a> 354This is the “require crypto authentication” option. 355 356<p class="noindent">This option has some usage constraints. It: 357 <ul> 358<li>must not appear in combination with any of the following options: 359authnoreq. 360</ul> 361 362 <p>Require cryptographic authentication for broadcast client, 363multicast client and symmetric passive associations. 364This is the default. 365<div class="node"> 366<p><hr> 367<a name="ntpd-authnoreq"></a> 368Next: <a rel="next" accesskey="n" href="#ntpd-configfile">ntpd configfile</a>, 369Previous: <a rel="previous" accesskey="p" href="#ntpd-authreq">ntpd authreq</a>, 370Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 371 372</div> 373 374<h4 class="subsection">authnoreq option (-A)</h4> 375 376<p><a name="index-ntpd_002dauthnoreq-7"></a> 377This is the “do not require crypto authentication” option. 378 379<p class="noindent">This option has some usage constraints. It: 380 <ul> 381<li>must not appear in combination with any of the following options: 382authreq. 383</ul> 384 385 <p>Do not require cryptographic authentication for broadcast client, 386multicast client and symmetric passive associations. 387This is almost never a good idea. 388<div class="node"> 389<p><hr> 390<a name="ntpd-configfile"></a> 391Next: <a rel="next" accesskey="n" href="#ntpd-driftfile">ntpd driftfile</a>, 392Previous: <a rel="previous" accesskey="p" href="#ntpd-authnoreq">ntpd authnoreq</a>, 393Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 394 395</div> 396 397<h4 class="subsection">configfile option (-c)</h4> 398 399<p><a name="index-ntpd_002dconfigfile-8"></a> 400This is the “configuration file name” option. 401This option takes a string argument. 402The name and path of the configuration file, 403<samp><span class="file">/etc/ntp.conf</span></samp> 404by default. 405<div class="node"> 406<p><hr> 407<a name="ntpd-driftfile"></a> 408Next: <a rel="next" accesskey="n" href="#ntpd-panicgate">ntpd panicgate</a>, 409Previous: <a rel="previous" accesskey="p" href="#ntpd-configfile">ntpd configfile</a>, 410Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 411 412</div> 413 414<h4 class="subsection">driftfile option (-f)</h4> 415 416<p><a name="index-ntpd_002ddriftfile-9"></a> 417This is the “frequency drift file name” option. 418This option takes a string argument. 419The name and path of the frequency file, 420<samp><span class="file">/etc/ntp.drift</span></samp> 421by default. 422This is the same operation as the 423<code>driftfile</code> <kbd>driftfile</kbd> 424configuration specification in the 425<samp><span class="file">/etc/ntp.conf</span></samp> 426file. 427<div class="node"> 428<p><hr> 429<a name="ntpd-panicgate"></a> 430Next: <a rel="next" accesskey="n" href="#ntpd-force_002dstep_002donce">ntpd force-step-once</a>, 431Previous: <a rel="previous" accesskey="p" href="#ntpd-driftfile">ntpd driftfile</a>, 432Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 433 434</div> 435 436<h4 class="subsection">panicgate option (-g)</h4> 437 438<p><a name="index-ntpd_002dpanicgate-10"></a> 439This is the “allow the first adjustment to be big” option. 440 441<p class="noindent">This option has some usage constraints. It: 442 <ul> 443<li>may appear an unlimited number of times. 444</ul> 445 446 <p>Normally, 447<code>ntpd</code> 448exits 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, 449<code>ntpd</code> 450will exit with a message to the system log. This option can be used with the 451<code>-q</code> 452and 453<code>-x</code> 454options. 455See the 456<code>tinker</code> 457configuration file directive for other options. 458<div class="node"> 459<p><hr> 460<a name="ntpd-force-step-once"></a> 461<a name="ntpd-force_002dstep_002donce"></a> 462Next: <a rel="next" accesskey="n" href="#ntpd-jaildir">ntpd jaildir</a>, 463Previous: <a rel="previous" accesskey="p" href="#ntpd-panicgate">ntpd panicgate</a>, 464Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 465 466</div> 467 468<h4 class="subsection">force-step-once option (-G)</h4> 469 470<p><a name="index-ntpd_002dforce_002dstep_002donce-11"></a> 471This is the “step any initial offset correction.” option. 472Normally, 473<code>ntpd</code> 474steps the time if the time offset exceeds the step threshold, 475which is 128 ms by default, and otherwise slews the time. 476This option forces the initial offset correction to be stepped, 477so the highest time accuracy can be achieved quickly. 478However, this may also cause the time to be stepped back 479so this option must not be used if 480applications requiring monotonic time are running. 481See the <code>tinker</code> configuration file directive for other options. 482<div class="node"> 483<p><hr> 484<a name="ntpd-jaildir"></a> 485Next: <a rel="next" accesskey="n" href="#ntpd-interface">ntpd interface</a>, 486Previous: <a rel="previous" accesskey="p" href="#ntpd-force_002dstep_002donce">ntpd force-step-once</a>, 487Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 488 489</div> 490 491<h4 class="subsection">jaildir option (-i)</h4> 492 493<p><a name="index-ntpd_002djaildir-12"></a> 494This is the “jail directory” option. 495This option takes a string argument. 496 497<p class="noindent">This option has some usage constraints. It: 498 <ul> 499<li>must be compiled in by defining <code>HAVE_DROPROOT</code> during the compilation. 500</ul> 501 502 <p>Chroot the server to the directory 503<kbd>jaildir</kbd> 504. 505This option also implies that the server attempts to drop root privileges at startup. 506You may need to also specify a 507<code>-u</code> 508option. 509This option is only available if the OS supports adjusting the clock 510without full root privileges. 511This option is supported under NetBSD (configure with 512<code>--enable-clockctl</code>) or Linux (configure with 513<code>--enable-linuxcaps</code>) or Solaris (configure with <code>--enable-solarisprivs</code>). 514<div class="node"> 515<p><hr> 516<a name="ntpd-interface"></a> 517Next: <a rel="next" accesskey="n" href="#ntpd-keyfile">ntpd keyfile</a>, 518Previous: <a rel="previous" accesskey="p" href="#ntpd-jaildir">ntpd jaildir</a>, 519Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 520 521</div> 522 523<h4 class="subsection">interface option (-I)</h4> 524 525<p><a name="index-ntpd_002dinterface-13"></a> 526This is the “listen on an interface name or address” option. 527This option takes a string argument <samp><span class="file">iface</span></samp>. 528 529<p class="noindent">This option has some usage constraints. It: 530 <ul> 531<li>may appear an unlimited number of times. 532</ul> 533 534 <p>Open the network address given, or all the addresses associated with the 535given interface name. This option may appear multiple times. This option 536also implies not opening other addresses, except wildcard and localhost. 537This option is deprecated. Please consider using the configuration file 538<code>interface</code> command, which is more versatile. 539<div class="node"> 540<p><hr> 541<a name="ntpd-keyfile"></a> 542Next: <a rel="next" accesskey="n" href="#ntpd-logfile">ntpd logfile</a>, 543Previous: <a rel="previous" accesskey="p" href="#ntpd-interface">ntpd interface</a>, 544Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 545 546</div> 547 548<h4 class="subsection">keyfile option (-k)</h4> 549 550<p><a name="index-ntpd_002dkeyfile-14"></a> 551This is the “path to symmetric keys” option. 552This option takes a string argument. 553Specify the name and path of the symmetric key file. 554<samp><span class="file">/etc/ntp.keys</span></samp> 555is the default. 556This is the same operation as the 557<code>keys</code> <kbd>keyfile</kbd> 558configuration file directive. 559<div class="node"> 560<p><hr> 561<a name="ntpd-logfile"></a> 562Next: <a rel="next" accesskey="n" href="#ntpd-novirtualips">ntpd novirtualips</a>, 563Previous: <a rel="previous" accesskey="p" href="#ntpd-keyfile">ntpd keyfile</a>, 564Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 565 566</div> 567 568<h4 class="subsection">logfile option (-l)</h4> 569 570<p><a name="index-ntpd_002dlogfile-15"></a> 571This is the “path to the log file” option. 572This option takes a string argument. 573Specify the name and path of the log file. 574The default is the system log file. 575This is the same operation as the 576<code>logfile</code> <kbd>logfile</kbd> 577configuration file directive. 578<div class="node"> 579<p><hr> 580<a name="ntpd-novirtualips"></a> 581Next: <a rel="next" accesskey="n" href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>, 582Previous: <a rel="previous" accesskey="p" href="#ntpd-logfile">ntpd logfile</a>, 583Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 584 585</div> 586 587<h4 class="subsection">novirtualips option (-L)</h4> 588 589<p><a name="index-ntpd_002dnovirtualips-16"></a> 590This is the “do not listen to virtual interfaces” option. 591Do not listen to virtual interfaces, defined as those with 592names containing a colon. This option is deprecated. Please 593consider using the configuration file <code>interface</code> command, which 594is more versatile. 595<div class="node"> 596<p><hr> 597<a name="ntpd-modifymmtimer"></a> 598Next: <a rel="next" accesskey="n" href="#ntpd-nice">ntpd nice</a>, 599Previous: <a rel="previous" accesskey="p" href="#ntpd-novirtualips">ntpd novirtualips</a>, 600Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 601 602</div> 603 604<h4 class="subsection">modifymmtimer option (-M)</h4> 605 606<p><a name="index-ntpd_002dmodifymmtimer-17"></a> 607This is the “modify multimedia timer (windows only)” option. 608 609<p class="noindent">This option has some usage constraints. It: 610 <ul> 611<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 612</ul> 613 614 <p>Set the Windows Multimedia Timer to highest resolution. This 615ensures the resolution does not change while ntpd is running, 616avoiding timekeeping glitches associated with changes. 617<div class="node"> 618<p><hr> 619<a name="ntpd-nice"></a> 620Next: <a rel="next" accesskey="n" href="#ntpd-pidfile">ntpd pidfile</a>, 621Previous: <a rel="previous" accesskey="p" href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>, 622Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 623 624</div> 625 626<h4 class="subsection">nice option (-N)</h4> 627 628<p><a name="index-ntpd_002dnice-18"></a> 629This is the “run at high priority” option. 630To the extent permitted by the operating system, run 631<code>ntpd</code> 632at the highest priority. 633<div class="node"> 634<p><hr> 635<a name="ntpd-pidfile"></a> 636Next: <a rel="next" accesskey="n" href="#ntpd-priority">ntpd priority</a>, 637Previous: <a rel="previous" accesskey="p" href="#ntpd-nice">ntpd nice</a>, 638Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 639 640</div> 641 642<h4 class="subsection">pidfile option (-p)</h4> 643 644<p><a name="index-ntpd_002dpidfile-19"></a> 645This is the “path to the pid file” option. 646This option takes a string argument. 647Specify the name and path of the file used to record 648<code>ntpd</code>'s 649process ID. 650This is the same operation as the 651<code>pidfile</code> <kbd>pidfile</kbd> 652configuration file directive. 653<div class="node"> 654<p><hr> 655<a name="ntpd-priority"></a> 656Next: <a rel="next" accesskey="n" href="#ntpd-quit">ntpd quit</a>, 657Previous: <a rel="previous" accesskey="p" href="#ntpd-pidfile">ntpd pidfile</a>, 658Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 659 660</div> 661 662<h4 class="subsection">priority option (-P)</h4> 663 664<p><a name="index-ntpd_002dpriority-20"></a> 665This is the “process priority” option. 666This option takes a number argument. 667To the extent permitted by the operating system, run 668<code>ntpd</code> 669at the specified 670<code>sched_setscheduler(SCHED_FIFO)</code> 671priority. 672<div class="node"> 673<p><hr> 674<a name="ntpd-quit"></a> 675Next: <a rel="next" accesskey="n" href="#ntpd-propagationdelay">ntpd propagationdelay</a>, 676Previous: <a rel="previous" accesskey="p" href="#ntpd-priority">ntpd priority</a>, 677Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 678 679</div> 680 681<h4 class="subsection">quit option (-q)</h4> 682 683<p><a name="index-ntpd_002dquit-21"></a> 684This is the “set the time and quit” option. 685 686<p class="noindent">This option has some usage constraints. It: 687 <ul> 688<li>must not appear in combination with any of the following options: 689saveconfigquit, wait-sync. 690</ul> 691 692 <p><code>ntpd</code> 693will not daemonize and will exit after the clock is first 694synchronized. This behavior mimics that of the 695<code>ntpdate</code> 696program, which will soon be replaced with a shell script. 697The 698<code>-g</code> 699and 700<code>-x</code> 701options can be used with this option. 702Note: The kernel time discipline is disabled with this option. 703<div class="node"> 704<p><hr> 705<a name="ntpd-propagationdelay"></a> 706Next: <a rel="next" accesskey="n" href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>, 707Previous: <a rel="previous" accesskey="p" href="#ntpd-quit">ntpd quit</a>, 708Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 709 710</div> 711 712<h4 class="subsection">propagationdelay option (-r)</h4> 713 714<p><a name="index-ntpd_002dpropagationdelay-22"></a> 715This is the “broadcast/propagation delay” option. 716This option takes a string argument. 717Specify 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. 718<div class="node"> 719<p><hr> 720<a name="ntpd-saveconfigquit"></a> 721Next: <a rel="next" accesskey="n" href="#ntpd-statsdir">ntpd statsdir</a>, 722Previous: <a rel="previous" accesskey="p" href="#ntpd-propagationdelay">ntpd propagationdelay</a>, 723Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 724 725</div> 726 727<h4 class="subsection">saveconfigquit option</h4> 728 729<p><a name="index-ntpd_002dsaveconfigquit-23"></a> 730This is the “save parsed configuration and quit” option. 731This option takes a string argument. 732 733<p class="noindent">This option has some usage constraints. It: 734 <ul> 735<li>must be compiled in by defining <code>SAVECONFIG</code> during the compilation. 736<li>must not appear in combination with any of the following options: 737quit, wait-sync. 738</ul> 739 740 <p>Cause <code>ntpd</code> to parse its startup configuration file and save an 741equivalent to the given filename and exit. This option was 742designed for automated testing. 743<div class="node"> 744<p><hr> 745<a name="ntpd-statsdir"></a> 746Next: <a rel="next" accesskey="n" href="#ntpd-trustedkey">ntpd trustedkey</a>, 747Previous: <a rel="previous" accesskey="p" href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>, 748Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 749 750</div> 751 752<h4 class="subsection">statsdir option (-s)</h4> 753 754<p><a name="index-ntpd_002dstatsdir-24"></a> 755This is the “statistics file location” option. 756This option takes a string argument. 757Specify the directory path for files created by the statistics facility. 758This is the same operation as the 759<code>statsdir</code> <kbd>statsdir</kbd> 760configuration file directive. 761<div class="node"> 762<p><hr> 763<a name="ntpd-trustedkey"></a> 764Next: <a rel="next" accesskey="n" href="#ntpd-user">ntpd user</a>, 765Previous: <a rel="previous" accesskey="p" href="#ntpd-statsdir">ntpd statsdir</a>, 766Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 767 768</div> 769 770<h4 class="subsection">trustedkey option (-t)</h4> 771 772<p><a name="index-ntpd_002dtrustedkey-25"></a> 773This is the “trusted key number” option. 774This option takes a string argument <samp><span class="file">tkey</span></samp>. 775 776<p class="noindent">This option has some usage constraints. It: 777 <ul> 778<li>may appear an unlimited number of times. 779</ul> 780 781 <p>Add the specified key number to the trusted key list. 782<div class="node"> 783<p><hr> 784<a name="ntpd-user"></a> 785Next: <a rel="next" accesskey="n" href="#ntpd-updateinterval">ntpd updateinterval</a>, 786Previous: <a rel="previous" accesskey="p" href="#ntpd-trustedkey">ntpd trustedkey</a>, 787Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 788 789</div> 790 791<h4 class="subsection">user option (-u)</h4> 792 793<p><a name="index-ntpd_002duser-26"></a> 794This is the “run as userid (or userid:groupid)” option. 795This option takes a string argument. 796 797<p class="noindent">This option has some usage constraints. It: 798 <ul> 799<li>must be compiled in by defining <code>HAVE_DROPROOT</code> during the compilation. 800</ul> 801 802 <p>Specify a user, and optionally a group, to switch to. 803This option is only available if the OS supports adjusting the clock 804without full root privileges. 805This option is supported under NetBSD (configure with 806<code>--enable-clockctl</code>) or Linux (configure with 807<code>--enable-linuxcaps</code>) or Solaris (configure with <code>--enable-solarisprivs</code>). 808<div class="node"> 809<p><hr> 810<a name="ntpd-updateinterval"></a> 811Next: <a rel="next" accesskey="n" href="#ntpd-wait_002dsync">ntpd wait-sync</a>, 812Previous: <a rel="previous" accesskey="p" href="#ntpd-user">ntpd user</a>, 813Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 814 815</div> 816 817<h4 class="subsection">updateinterval option (-U)</h4> 818 819<p><a name="index-ntpd_002dupdateinterval-27"></a> 820This is the “interval in seconds between scans for new or dropped interfaces” option. 821This option takes a number argument. 822Give the time in seconds between two scans for new or dropped interfaces. 823For systems with routing socket support the scans will be performed shortly after the interface change 824has been detected by the system. 825Use 0 to disable scanning. 60 seconds is the minimum time between scans. 826<div class="node"> 827<p><hr> 828<a name="ntpd-wait-sync"></a> 829<a name="ntpd-wait_002dsync"></a> 830Next: <a rel="next" accesskey="n" href="#ntpd-slew">ntpd slew</a>, 831Previous: <a rel="previous" accesskey="p" href="#ntpd-updateinterval">ntpd updateinterval</a>, 832Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 833 834</div> 835 836<h4 class="subsection">wait-sync option (-w)</h4> 837 838<p><a name="index-ntpd_002dwait_002dsync-28"></a> 839This is the “seconds to wait for first clock sync” option. 840This option takes a number argument. 841 842<p class="noindent">This option has some usage constraints. It: 843 <ul> 844<li>must be compiled in by defining <code>HAVE_WORKING_FORK</code> during the compilation. 845<li>must not appear in combination with any of the following options: 846nofork, quit, saveconfigquit. 847</ul> 848 849 <p>If greater than zero, alters <code>ntpd</code>'s behavior when forking to 850daemonize. Instead of exiting with status 0 immediately after 851the fork, the parent waits up to the specified number of 852seconds for the child to first synchronize the clock. The exit 853status is zero (success) if the clock was synchronized, 854otherwise it is <code>ETIMEDOUT</code>. 855This provides the option for a script starting <code>ntpd</code> to easily 856wait for the first set of the clock before proceeding. 857<div class="node"> 858<p><hr> 859<a name="ntpd-slew"></a> 860Next: <a rel="next" accesskey="n" href="#ntpd-usepcc">ntpd usepcc</a>, 861Previous: <a rel="previous" accesskey="p" href="#ntpd-wait_002dsync">ntpd wait-sync</a>, 862Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 863 864</div> 865 866<h4 class="subsection">slew option (-x)</h4> 867 868<p><a name="index-ntpd_002dslew-29"></a> 869This is the “slew up to 600 seconds” option. 870Normally, 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. 871This option sets the threshold to 600 s, which is well within the accuracy window to set the clock manually. 872Note: 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. 873Thus, an adjustment as much as 600 s will take almost 14 days to complete. 874This option can be used with the 875<code>-g</code> 876and 877<code>-q</code> 878options. 879See the 880<code>tinker</code> 881configuration file directive for other options. 882Note: The kernel time discipline is disabled with this option. 883<div class="node"> 884<p><hr> 885<a name="ntpd-usepcc"></a> 886Next: <a rel="next" accesskey="n" href="#ntpd-pccfreq">ntpd pccfreq</a>, 887Previous: <a rel="previous" accesskey="p" href="#ntpd-slew">ntpd slew</a>, 888Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 889 890</div> 891 892<h4 class="subsection">usepcc option</h4> 893 894<p><a name="index-ntpd_002dusepcc-30"></a> 895This is the “use cpu cycle counter (windows only)” option. 896 897<p class="noindent">This option has some usage constraints. It: 898 <ul> 899<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 900</ul> 901 902 <p>Attempt to substitute the CPU counter for <code>QueryPerformanceCounter</code>. 903The CPU counter and <code>QueryPerformanceCounter</code> are compared, and if 904they have the same frequency, the CPU counter (RDTSC on x86) is 905used directly, saving the overhead of a system call. 906<div class="node"> 907<p><hr> 908<a name="ntpd-pccfreq"></a> 909Next: <a rel="next" accesskey="n" href="#ntpd-mdns">ntpd mdns</a>, 910Previous: <a rel="previous" accesskey="p" href="#ntpd-usepcc">ntpd usepcc</a>, 911Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 912 913</div> 914 915<h4 class="subsection">pccfreq option</h4> 916 917<p><a name="index-ntpd_002dpccfreq-31"></a> 918This is the “force cpu cycle counter use (windows only)” option. 919This option takes a string argument. 920 921<p class="noindent">This option has some usage constraints. It: 922 <ul> 923<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 924</ul> 925 926 <p>Force substitution the CPU counter for <code>QueryPerformanceCounter</code>. 927The CPU counter (RDTSC on x86) is used unconditionally with the 928given frequency (in Hz). 929<div class="node"> 930<p><hr> 931<a name="ntpd-mdns"></a> 932Next: <a rel="next" accesskey="n" href="#ntpd-config">ntpd config</a>, 933Previous: <a rel="previous" accesskey="p" href="#ntpd-pccfreq">ntpd pccfreq</a>, 934Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 935 936</div> 937 938<h4 class="subsection">mdns option (-m)</h4> 939 940<p><a name="index-ntpd_002dmdns-32"></a> 941This is the “register with mdns as a ntp server” option. 942 943<p class="noindent">This option has some usage constraints. It: 944 <ul> 945<li>must be compiled in by defining <code>HAVE_DNSREGISTRATION</code> during the compilation. 946</ul> 947 948 <p>Registers as an NTP server with the local mDNS server which allows 949the server to be discovered via mDNS client lookup. 950 951<div class="node"> 952<p><hr> 953<a name="ntpd-config"></a> 954Next: <a rel="next" accesskey="n" href="#ntpd-exit-status">ntpd exit status</a>, 955Previous: <a rel="previous" accesskey="p" href="#ntpd-mdns">ntpd mdns</a>, 956Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 957 958</div> 959 960<h4 class="subsection">presetting/configuring ntpd</h4> 961 962<p>Any option that is not marked as <i>not presettable</i> may be preset by 963loading values from environment variables named <code>NTPD</code> and <code>NTPD_<OPTION_NAME></code>. <code><OPTION_NAME></code> must be one of 964the options listed above in upper case and segmented with underscores. 965The <code>NTPD</code> variable will be tokenized and parsed like 966the command line. The remaining variables are tested for existence and their 967values are treated like option arguments. 968 969 <p>The command line options relating to configuration and/or usage help are: 970 971<h5 class="subsubheading">version (-)</h5> 972 973<p>Print the program version to standard out, optionally with licensing 974information, then exit 0. The optional argument specifies how much licensing 975detail to provide. The default is to print just the version. The licensing infomation may be selected with an option argument. 976Only the first letter of the argument is examined: 977 978 <dl> 979<dt>`<samp><span class="samp">version</span></samp>'<dd>Only print the version. This is the default. 980<br><dt>`<samp><span class="samp">copyright</span></samp>'<dd>Name the copyright usage licensing terms. 981<br><dt>`<samp><span class="samp">verbose</span></samp>'<dd>Print the full copyright usage licensing terms. 982</dl> 983 984<div class="node"> 985<p><hr> 986<a name="ntpd-exit-status"></a> 987Next: <a rel="next" accesskey="n" href="#ntpd-Usage">ntpd Usage</a>, 988Previous: <a rel="previous" accesskey="p" href="#ntpd-config">ntpd config</a>, 989Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 990 991</div> 992 993<h4 class="subsection">ntpd exit status</h4> 994 995<p>One of the following exit values will be returned: 996 <dl> 997<dt>`<samp><span class="samp">0 (EXIT_SUCCESS)</span></samp>'<dd>Successful program execution. 998<br><dt>`<samp><span class="samp">1 (EXIT_FAILURE)</span></samp>'<dd>The operation failed or the command syntax was not valid. 999</dl> 1000 <div class="node"> 1001<p><hr> 1002<a name="ntpd-Usage"></a> 1003Next: <a rel="next" accesskey="n" href="#ntpd-Files">ntpd Files</a>, 1004Previous: <a rel="previous" accesskey="p" href="#ntpd-exit-status">ntpd exit status</a>, 1005Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 1006 1007</div> 1008 1009<h4 class="subsection">ntpd Usage</h4> 1010 1011<div class="node"> 1012<p><hr> 1013<a name="ntpd-Files"></a> 1014Next: <a rel="next" accesskey="n" href="#ntpd-See-Also">ntpd See Also</a>, 1015Previous: <a rel="previous" accesskey="p" href="#ntpd-Usage">ntpd Usage</a>, 1016Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 1017 1018</div> 1019 1020<h4 class="subsection">ntpd Files</h4> 1021 1022<div class="node"> 1023<p><hr> 1024<a name="ntpd-See-Also"></a> 1025Next: <a rel="next" accesskey="n" href="#ntpd-Bugs">ntpd Bugs</a>, 1026Previous: <a rel="previous" accesskey="p" href="#ntpd-Files">ntpd Files</a>, 1027Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 1028 1029</div> 1030 1031<h4 class="subsection">ntpd See Also</h4> 1032 1033<div class="node"> 1034<p><hr> 1035<a name="ntpd-Bugs"></a> 1036Next: <a rel="next" accesskey="n" href="#ntpd-Notes">ntpd Notes</a>, 1037Previous: <a rel="previous" accesskey="p" href="#ntpd-See-Also">ntpd See Also</a>, 1038Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 1039 1040</div> 1041 1042<h4 class="subsection">ntpd Bugs</h4> 1043 1044<div class="node"> 1045<p><hr> 1046<a name="ntpd-Notes"></a> 1047Previous: <a rel="previous" accesskey="p" href="#ntpd-Bugs">ntpd Bugs</a>, 1048Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 1049 1050</div> 1051 1052<h4 class="subsection">ntpd Notes</h4> 1053 1054<div class="node"> 1055<p><hr> 1056<a name="Usage"></a> 1057 1058 1059</div> 1060 1061<!-- node-name, next, previous, up --> 1062<h3 class="section">Usage</h3> 1063 1064