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 4.2.8p1 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. 4.2.8p1-RC2 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</pre> 291 <div class="node"> 292<p><hr> 293<a name="ntpd-ipv4"></a>Next: <a rel="next" accesskey="n" href="#ntpd-ipv6">ntpd ipv6</a>, 294Previous: <a rel="previous" accesskey="p" href="#ntpd-usage">ntpd usage</a>, 295Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 296<br> 297</div> 298 299<h4 class="subsection">ipv4 option (-4)</h4> 300 301<p><a name="index-ntpd_002dipv4-4"></a> 302This is the “force ipv4 dns name resolution” option. 303 304<p class="noindent">This option has some usage constraints. It: 305 <ul> 306<li>must not appear in combination with any of the following options: 307ipv6. 308</ul> 309 310 <p>Force DNS resolution of following host names on the command line 311to the IPv4 namespace. 312<div class="node"> 313<p><hr> 314<a name="ntpd-ipv6"></a>Next: <a rel="next" accesskey="n" href="#ntpd-authreq">ntpd authreq</a>, 315Previous: <a rel="previous" accesskey="p" href="#ntpd-ipv4">ntpd ipv4</a>, 316Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 317<br> 318</div> 319 320<h4 class="subsection">ipv6 option (-6)</h4> 321 322<p><a name="index-ntpd_002dipv6-5"></a> 323This is the “force ipv6 dns name resolution” option. 324 325<p class="noindent">This option has some usage constraints. It: 326 <ul> 327<li>must not appear in combination with any of the following options: 328ipv4. 329</ul> 330 331 <p>Force DNS resolution of following host names on the command line 332to the IPv6 namespace. 333<div class="node"> 334<p><hr> 335<a name="ntpd-authreq"></a>Next: <a rel="next" accesskey="n" href="#ntpd-authnoreq">ntpd authnoreq</a>, 336Previous: <a rel="previous" accesskey="p" href="#ntpd-ipv6">ntpd ipv6</a>, 337Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 338<br> 339</div> 340 341<h4 class="subsection">authreq option (-a)</h4> 342 343<p><a name="index-ntpd_002dauthreq-6"></a> 344This is the “require crypto authentication” option. 345 346<p class="noindent">This option has some usage constraints. It: 347 <ul> 348<li>must not appear in combination with any of the following options: 349authnoreq. 350</ul> 351 352 <p>Require cryptographic authentication for broadcast client, 353multicast client and symmetric passive associations. 354This is the default. 355<div class="node"> 356<p><hr> 357<a name="ntpd-authnoreq"></a>Next: <a rel="next" accesskey="n" href="#ntpd-configfile">ntpd configfile</a>, 358Previous: <a rel="previous" accesskey="p" href="#ntpd-authreq">ntpd authreq</a>, 359Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 360<br> 361</div> 362 363<h4 class="subsection">authnoreq option (-A)</h4> 364 365<p><a name="index-ntpd_002dauthnoreq-7"></a> 366This is the “do not require crypto authentication” option. 367 368<p class="noindent">This option has some usage constraints. It: 369 <ul> 370<li>must not appear in combination with any of the following options: 371authreq. 372</ul> 373 374 <p>Do not require cryptographic authentication for broadcast client, 375multicast client and symmetric passive associations. 376This is almost never a good idea. 377<div class="node"> 378<p><hr> 379<a name="ntpd-configfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-driftfile">ntpd driftfile</a>, 380Previous: <a rel="previous" accesskey="p" href="#ntpd-authnoreq">ntpd authnoreq</a>, 381Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 382<br> 383</div> 384 385<h4 class="subsection">configfile option (-c)</h4> 386 387<p><a name="index-ntpd_002dconfigfile-8"></a> 388This is the “configuration file name” option. 389This option takes a string argument. 390The name and path of the configuration file, 391<span class="file">/etc/ntp.conf</span> 392by default. 393<div class="node"> 394<p><hr> 395<a name="ntpd-driftfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-panicgate">ntpd panicgate</a>, 396Previous: <a rel="previous" accesskey="p" href="#ntpd-configfile">ntpd configfile</a>, 397Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 398<br> 399</div> 400 401<h4 class="subsection">driftfile option (-f)</h4> 402 403<p><a name="index-ntpd_002ddriftfile-9"></a> 404This is the “frequency drift file name” option. 405This option takes a string argument. 406The name and path of the frequency file, 407<span class="file">/etc/ntp.drift</span> 408by default. 409This is the same operation as the 410<code>driftfile</code> <kbd>driftfile</kbd> 411configuration specification in the 412<span class="file">/etc/ntp.conf</span> 413file. 414<div class="node"> 415<p><hr> 416<a name="ntpd-panicgate"></a>Next: <a rel="next" accesskey="n" href="#ntpd-jaildir">ntpd jaildir</a>, 417Previous: <a rel="previous" accesskey="p" href="#ntpd-driftfile">ntpd driftfile</a>, 418Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 419<br> 420</div> 421 422<h4 class="subsection">panicgate option (-g)</h4> 423 424<p><a name="index-ntpd_002dpanicgate-10"></a> 425This is the “allow the first adjustment to be big” option. 426 427<p class="noindent">This option has some usage constraints. It: 428 <ul> 429<li>may appear an unlimited number of times. 430</ul> 431 432 <p>Normally, 433<code>ntpd</code> 434exits 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, 435<code>ntpd</code> 436will exit with a message to the system log. This option can be used with the 437<code>-q</code> 438and 439<code>-x</code> 440options. 441See the 442<code>tinker</code> 443configuration file directive for other options. 444<div class="node"> 445<p><hr> 446<a name="ntpd-jaildir"></a>Next: <a rel="next" accesskey="n" href="#ntpd-interface">ntpd interface</a>, 447Previous: <a rel="previous" accesskey="p" href="#ntpd-panicgate">ntpd panicgate</a>, 448Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 449<br> 450</div> 451 452<h4 class="subsection">jaildir option (-i)</h4> 453 454<p><a name="index-ntpd_002djaildir-11"></a> 455This is the “jail directory” option. 456This option takes a string argument. 457 458<p class="noindent">This option has some usage constraints. It: 459 <ul> 460<li>must be compiled in by defining <code>HAVE_DROPROOT</code> during the compilation. 461</ul> 462 463 <p>Chroot the server to the directory 464<kbd>jaildir</kbd> 465. 466This option also implies that the server attempts to drop root privileges at startup. 467You may need to also specify a 468<code>-u</code> 469option. 470This option is only available if the OS supports adjusting the clock 471without full root privileges. 472This option is supported under NetBSD (configure with 473<code>--enable-clockctl</code>) or Linux (configure with 474<code>--enable-linuxcaps</code>) or Solaris (configure with <code>--enable-solarisprivs</code>). 475<div class="node"> 476<p><hr> 477<a name="ntpd-interface"></a>Next: <a rel="next" accesskey="n" href="#ntpd-keyfile">ntpd keyfile</a>, 478Previous: <a rel="previous" accesskey="p" href="#ntpd-jaildir">ntpd jaildir</a>, 479Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 480<br> 481</div> 482 483<h4 class="subsection">interface option (-I)</h4> 484 485<p><a name="index-ntpd_002dinterface-12"></a> 486This is the “listen on an interface name or address” option. 487This option takes a string argument <span class="file">iface</span>. 488 489<p class="noindent">This option has some usage constraints. It: 490 <ul> 491<li>may appear an unlimited number of times. 492</ul> 493 494 <p>Open the network address given, or all the addresses associated with the 495given interface name. This option may appear multiple times. This option 496also implies not opening other addresses, except wildcard and localhost. 497This option is deprecated. Please consider using the configuration file 498<code>interface</code> command, which is more versatile. 499<div class="node"> 500<p><hr> 501<a name="ntpd-keyfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-logfile">ntpd logfile</a>, 502Previous: <a rel="previous" accesskey="p" href="#ntpd-interface">ntpd interface</a>, 503Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 504<br> 505</div> 506 507<h4 class="subsection">keyfile option (-k)</h4> 508 509<p><a name="index-ntpd_002dkeyfile-13"></a> 510This is the “path to symmetric keys” option. 511This option takes a string argument. 512Specify the name and path of the symmetric key file. 513<span class="file">/etc/ntp.keys</span> 514is the default. 515This is the same operation as the 516<code>keys</code> <kbd>keyfile</kbd> 517configuration file directive. 518<div class="node"> 519<p><hr> 520<a name="ntpd-logfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-novirtualips">ntpd novirtualips</a>, 521Previous: <a rel="previous" accesskey="p" href="#ntpd-keyfile">ntpd keyfile</a>, 522Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 523<br> 524</div> 525 526<h4 class="subsection">logfile option (-l)</h4> 527 528<p><a name="index-ntpd_002dlogfile-14"></a> 529This is the “path to the log file” option. 530This option takes a string argument. 531Specify the name and path of the log file. 532The default is the system log file. 533This is the same operation as the 534<code>logfile</code> <kbd>logfile</kbd> 535configuration file directive. 536<div class="node"> 537<p><hr> 538<a name="ntpd-novirtualips"></a>Next: <a rel="next" accesskey="n" href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>, 539Previous: <a rel="previous" accesskey="p" href="#ntpd-logfile">ntpd logfile</a>, 540Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 541<br> 542</div> 543 544<h4 class="subsection">novirtualips option (-L)</h4> 545 546<p><a name="index-ntpd_002dnovirtualips-15"></a> 547This is the “do not listen to virtual interfaces” option. 548Do not listen to virtual interfaces, defined as those with 549names containing a colon. This option is deprecated. Please 550consider using the configuration file <code>interface</code> command, which 551is more versatile. 552<div class="node"> 553<p><hr> 554<a name="ntpd-modifymmtimer"></a>Next: <a rel="next" accesskey="n" href="#ntpd-nice">ntpd nice</a>, 555Previous: <a rel="previous" accesskey="p" href="#ntpd-novirtualips">ntpd novirtualips</a>, 556Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 557<br> 558</div> 559 560<h4 class="subsection">modifymmtimer option (-M)</h4> 561 562<p><a name="index-ntpd_002dmodifymmtimer-16"></a> 563This is the “modify multimedia timer (windows only)” option. 564 565<p class="noindent">This option has some usage constraints. It: 566 <ul> 567<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 568</ul> 569 570 <p>Set the Windows Multimedia Timer to highest resolution. This 571ensures the resolution does not change while ntpd is running, 572avoiding timekeeping glitches associated with changes. 573<div class="node"> 574<p><hr> 575<a name="ntpd-nice"></a>Next: <a rel="next" accesskey="n" href="#ntpd-pidfile">ntpd pidfile</a>, 576Previous: <a rel="previous" accesskey="p" href="#ntpd-modifymmtimer">ntpd modifymmtimer</a>, 577Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 578<br> 579</div> 580 581<h4 class="subsection">nice option (-N)</h4> 582 583<p><a name="index-ntpd_002dnice-17"></a> 584This is the “run at high priority” option. 585To the extent permitted by the operating system, run 586<code>ntpd</code> 587at the highest priority. 588<div class="node"> 589<p><hr> 590<a name="ntpd-pidfile"></a>Next: <a rel="next" accesskey="n" href="#ntpd-priority">ntpd priority</a>, 591Previous: <a rel="previous" accesskey="p" href="#ntpd-nice">ntpd nice</a>, 592Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 593<br> 594</div> 595 596<h4 class="subsection">pidfile option (-p)</h4> 597 598<p><a name="index-ntpd_002dpidfile-18"></a> 599This is the “path to the pid file” option. 600This option takes a string argument. 601Specify the name and path of the file used to record 602<code>ntpd</code>'s 603process ID. 604This is the same operation as the 605<code>pidfile</code> <kbd>pidfile</kbd> 606configuration file directive. 607<div class="node"> 608<p><hr> 609<a name="ntpd-priority"></a>Next: <a rel="next" accesskey="n" href="#ntpd-quit">ntpd quit</a>, 610Previous: <a rel="previous" accesskey="p" href="#ntpd-pidfile">ntpd pidfile</a>, 611Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 612<br> 613</div> 614 615<h4 class="subsection">priority option (-P)</h4> 616 617<p><a name="index-ntpd_002dpriority-19"></a> 618This is the “process priority” option. 619This option takes a number argument. 620To the extent permitted by the operating system, run 621<code>ntpd</code> 622at the specified 623<code>sched_setscheduler(SCHED_FIFO)</code> 624priority. 625<div class="node"> 626<p><hr> 627<a name="ntpd-quit"></a>Next: <a rel="next" accesskey="n" href="#ntpd-propagationdelay">ntpd propagationdelay</a>, 628Previous: <a rel="previous" accesskey="p" href="#ntpd-priority">ntpd priority</a>, 629Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 630<br> 631</div> 632 633<h4 class="subsection">quit option (-q)</h4> 634 635<p><a name="index-ntpd_002dquit-20"></a> 636This is the “set the time and quit” option. 637 638<p class="noindent">This option has some usage constraints. It: 639 <ul> 640<li>must not appear in combination with any of the following options: 641saveconfigquit, wait-sync. 642</ul> 643 644 <p><code>ntpd</code> 645will not daemonize and will exit after the clock is first 646synchronized. This behavior mimics that of the 647<code>ntpdate</code> 648program, which will soon be replaced with a shell script. 649The 650<code>-g</code> 651and 652<code>-x</code> 653options can be used with this option. 654Note: The kernel time discipline is disabled with this option. 655<div class="node"> 656<p><hr> 657<a name="ntpd-propagationdelay"></a>Next: <a rel="next" accesskey="n" href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>, 658Previous: <a rel="previous" accesskey="p" href="#ntpd-quit">ntpd quit</a>, 659Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 660<br> 661</div> 662 663<h4 class="subsection">propagationdelay option (-r)</h4> 664 665<p><a name="index-ntpd_002dpropagationdelay-21"></a> 666This is the “broadcast/propagation delay” option. 667This option takes a string argument. 668Specify 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. 669<div class="node"> 670<p><hr> 671<a name="ntpd-saveconfigquit"></a>Next: <a rel="next" accesskey="n" href="#ntpd-statsdir">ntpd statsdir</a>, 672Previous: <a rel="previous" accesskey="p" href="#ntpd-propagationdelay">ntpd propagationdelay</a>, 673Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 674<br> 675</div> 676 677<h4 class="subsection">saveconfigquit option</h4> 678 679<p><a name="index-ntpd_002dsaveconfigquit-22"></a> 680This is the “save parsed configuration and quit” option. 681This option takes a string argument. 682 683<p class="noindent">This option has some usage constraints. It: 684 <ul> 685<li>must be compiled in by defining <code>SAVECONFIG</code> during the compilation. 686<li>must not appear in combination with any of the following options: 687quit, wait-sync. 688</ul> 689 690 <p>Cause <code>ntpd</code> to parse its startup configuration file and save an 691equivalent to the given filename and exit. This option was 692designed for automated testing. 693<div class="node"> 694<p><hr> 695<a name="ntpd-statsdir"></a>Next: <a rel="next" accesskey="n" href="#ntpd-trustedkey">ntpd trustedkey</a>, 696Previous: <a rel="previous" accesskey="p" href="#ntpd-saveconfigquit">ntpd saveconfigquit</a>, 697Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 698<br> 699</div> 700 701<h4 class="subsection">statsdir option (-s)</h4> 702 703<p><a name="index-ntpd_002dstatsdir-23"></a> 704This is the “statistics file location” option. 705This option takes a string argument. 706Specify the directory path for files created by the statistics facility. 707This is the same operation as the 708<code>statsdir</code> <kbd>statsdir</kbd> 709configuration file directive. 710<div class="node"> 711<p><hr> 712<a name="ntpd-trustedkey"></a>Next: <a rel="next" accesskey="n" href="#ntpd-user">ntpd user</a>, 713Previous: <a rel="previous" accesskey="p" href="#ntpd-statsdir">ntpd statsdir</a>, 714Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 715<br> 716</div> 717 718<h4 class="subsection">trustedkey option (-t)</h4> 719 720<p><a name="index-ntpd_002dtrustedkey-24"></a> 721This is the “trusted key number” option. 722This option takes a string argument <span class="file">tkey</span>. 723 724<p class="noindent">This option has some usage constraints. It: 725 <ul> 726<li>may appear an unlimited number of times. 727</ul> 728 729 <p>Add the specified key number to the trusted key list. 730<div class="node"> 731<p><hr> 732<a name="ntpd-user"></a>Next: <a rel="next" accesskey="n" href="#ntpd-updateinterval">ntpd updateinterval</a>, 733Previous: <a rel="previous" accesskey="p" href="#ntpd-trustedkey">ntpd trustedkey</a>, 734Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 735<br> 736</div> 737 738<h4 class="subsection">user option (-u)</h4> 739 740<p><a name="index-ntpd_002duser-25"></a> 741This is the “run as userid (or userid:groupid)” option. 742This option takes a string argument. 743 744<p class="noindent">This option has some usage constraints. It: 745 <ul> 746<li>must be compiled in by defining <code>HAVE_DROPROOT</code> during the compilation. 747</ul> 748 749 <p>Specify a user, and optionally a group, to switch to. 750This option is only available if the OS supports adjusting the clock 751without full root privileges. 752This option is supported under NetBSD (configure with 753<code>--enable-clockctl</code>) or Linux (configure with 754<code>--enable-linuxcaps</code>) or Solaris (configure with <code>--enable-solarisprivs</code>). 755<div class="node"> 756<p><hr> 757<a name="ntpd-updateinterval"></a>Next: <a rel="next" accesskey="n" href="#ntpd-wait_002dsync">ntpd wait-sync</a>, 758Previous: <a rel="previous" accesskey="p" href="#ntpd-user">ntpd user</a>, 759Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 760<br> 761</div> 762 763<h4 class="subsection">updateinterval option (-U)</h4> 764 765<p><a name="index-ntpd_002dupdateinterval-26"></a> 766This is the “interval in seconds between scans for new or dropped interfaces” option. 767This option takes a number argument. 768Give the time in seconds between two scans for new or dropped interfaces. 769For systems with routing socket support the scans will be performed shortly after the interface change 770has been detected by the system. 771Use 0 to disable scanning. 60 seconds is the minimum time between scans. 772<div class="node"> 773<p><hr> 774<a name="ntpd-wait_002dsync"></a>Next: <a rel="next" accesskey="n" href="#ntpd-slew">ntpd slew</a>, 775Previous: <a rel="previous" accesskey="p" href="#ntpd-updateinterval">ntpd updateinterval</a>, 776Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 777<br> 778</div> 779 780<h4 class="subsection">wait-sync option (-w)</h4> 781 782<p><a name="index-ntpd_002dwait_002dsync-27"></a> 783This is the “seconds to wait for first clock sync” option. 784This option takes a number argument. 785 786<p class="noindent">This option has some usage constraints. It: 787 <ul> 788<li>must be compiled in by defining <code>HAVE_WORKING_FORK</code> during the compilation. 789<li>must not appear in combination with any of the following options: 790nofork, quit, saveconfigquit. 791</ul> 792 793 <p>If greater than zero, alters <code>ntpd</code>'s behavior when forking to 794daemonize. Instead of exiting with status 0 immediately after 795the fork, the parent waits up to the specified number of 796seconds for the child to first synchronize the clock. The exit 797status is zero (success) if the clock was synchronized, 798otherwise it is <code>ETIMEDOUT</code>. 799This provides the option for a script starting <code>ntpd</code> to easily 800wait for the first set of the clock before proceeding. 801<div class="node"> 802<p><hr> 803<a name="ntpd-slew"></a>Next: <a rel="next" accesskey="n" href="#ntpd-usepcc">ntpd usepcc</a>, 804Previous: <a rel="previous" accesskey="p" href="#ntpd-wait_002dsync">ntpd wait-sync</a>, 805Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 806<br> 807</div> 808 809<h4 class="subsection">slew option (-x)</h4> 810 811<p><a name="index-ntpd_002dslew-28"></a> 812This is the “slew up to 600 seconds” option. 813Normally, 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. 814This option sets the threshold to 600 s, which is well within the accuracy window to set the clock manually. 815Note: 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. 816Thus, an adjustment as much as 600 s will take almost 14 days to complete. 817This option can be used with the 818<code>-g</code> 819and 820<code>-q</code> 821options. 822See the 823<code>tinker</code> 824configuration file directive for other options. 825Note: The kernel time discipline is disabled with this option. 826<div class="node"> 827<p><hr> 828<a name="ntpd-usepcc"></a>Next: <a rel="next" accesskey="n" href="#ntpd-pccfreq">ntpd pccfreq</a>, 829Previous: <a rel="previous" accesskey="p" href="#ntpd-slew">ntpd slew</a>, 830Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 831<br> 832</div> 833 834<h4 class="subsection">usepcc option</h4> 835 836<p><a name="index-ntpd_002dusepcc-29"></a> 837This is the “use cpu cycle counter (windows only)” option. 838 839<p class="noindent">This option has some usage constraints. It: 840 <ul> 841<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 842</ul> 843 844 <p>Attempt to substitute the CPU counter for <code>QueryPerformanceCounter</code>. 845The CPU counter and <code>QueryPerformanceCounter</code> are compared, and if 846they have the same frequency, the CPU counter (RDTSC on x86) is 847used directly, saving the overhead of a system call. 848<div class="node"> 849<p><hr> 850<a name="ntpd-pccfreq"></a>Next: <a rel="next" accesskey="n" href="#ntpd-mdns">ntpd mdns</a>, 851Previous: <a rel="previous" accesskey="p" href="#ntpd-usepcc">ntpd usepcc</a>, 852Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 853<br> 854</div> 855 856<h4 class="subsection">pccfreq option</h4> 857 858<p><a name="index-ntpd_002dpccfreq-30"></a> 859This is the “force cpu cycle counter use (windows only)” option. 860This option takes a string argument. 861 862<p class="noindent">This option has some usage constraints. It: 863 <ul> 864<li>must be compiled in by defining <code>SYS_WINNT</code> during the compilation. 865</ul> 866 867 <p>Force substitution the CPU counter for <code>QueryPerformanceCounter</code>. 868The CPU counter (RDTSC on x86) is used unconditionally with the 869given frequency (in Hz). 870<div class="node"> 871<p><hr> 872<a name="ntpd-mdns"></a>Next: <a rel="next" accesskey="n" href="#ntpd-config">ntpd config</a>, 873Previous: <a rel="previous" accesskey="p" href="#ntpd-pccfreq">ntpd pccfreq</a>, 874Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 875<br> 876</div> 877 878<h4 class="subsection">mdns option (-m)</h4> 879 880<p><a name="index-ntpd_002dmdns-31"></a> 881This is the “register with mdns as a ntp server” option. 882 883<p class="noindent">This option has some usage constraints. It: 884 <ul> 885<li>must be compiled in by defining <code>HAVE_DNSREGISTRATION</code> during the compilation. 886</ul> 887 888 <p>Registers as an NTP server with the local mDNS server which allows 889the server to be discovered via mDNS client lookup. 890 891<div class="node"> 892<p><hr> 893<a name="ntpd-config"></a>Next: <a rel="next" accesskey="n" href="#ntpd-exit-status">ntpd exit status</a>, 894Previous: <a rel="previous" accesskey="p" href="#ntpd-mdns">ntpd mdns</a>, 895Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 896<br> 897</div> 898 899<h4 class="subsection">presetting/configuring ntpd</h4> 900 901<p>Any option that is not marked as <i>not presettable</i> may be preset by 902loading values from environment variables named <code>NTPD</code> and <code>NTPD_<OPTION_NAME></code>. <code><OPTION_NAME></code> must be one of 903the options listed above in upper case and segmented with underscores. 904The <code>NTPD</code> variable will be tokenized and parsed like 905the command line. The remaining variables are tested for existence and their 906values are treated like option arguments. 907 908 <p>The command line options relating to configuration and/or usage help are: 909 910<h5 class="subsubheading">version (-)</h5> 911 912<p>Print the program version to standard out, optionally with licensing 913information, then exit 0. The optional argument specifies how much licensing 914detail to provide. The default is to print just the version. The licensing infomation may be selected with an option argument. 915Only the first letter of the argument is examined: 916 917 <dl> 918<dt><span class="samp">version</span><dd>Only print the version. This is the default. 919<br><dt><span class="samp">copyright</span><dd>Name the copyright usage licensing terms. 920<br><dt><span class="samp">verbose</span><dd>Print the full copyright usage licensing terms. 921</dl> 922 923<div class="node"> 924<p><hr> 925<a name="ntpd-exit-status"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Usage">ntpd Usage</a>, 926Previous: <a rel="previous" accesskey="p" href="#ntpd-config">ntpd config</a>, 927Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 928<br> 929</div> 930 931<h4 class="subsection">ntpd exit status</h4> 932 933<p>One of the following exit values will be returned: 934 <dl> 935<dt><span class="samp">0 (EXIT_SUCCESS)</span><dd>Successful program execution. 936<br><dt><span class="samp">1 (EXIT_FAILURE)</span><dd>The operation failed or the command syntax was not valid. 937</dl> 938 <div class="node"> 939<p><hr> 940<a name="ntpd-Usage"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Files">ntpd Files</a>, 941Previous: <a rel="previous" accesskey="p" href="#ntpd-exit-status">ntpd exit status</a>, 942Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 943<br> 944</div> 945 946<h4 class="subsection">ntpd Usage</h4> 947 948<div class="node"> 949<p><hr> 950<a name="ntpd-Files"></a>Next: <a rel="next" accesskey="n" href="#ntpd-See-Also">ntpd See Also</a>, 951Previous: <a rel="previous" accesskey="p" href="#ntpd-Usage">ntpd Usage</a>, 952Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 953<br> 954</div> 955 956<h4 class="subsection">ntpd Files</h4> 957 958<div class="node"> 959<p><hr> 960<a name="ntpd-See-Also"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Bugs">ntpd Bugs</a>, 961Previous: <a rel="previous" accesskey="p" href="#ntpd-Files">ntpd Files</a>, 962Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 963<br> 964</div> 965 966<h4 class="subsection">ntpd See Also</h4> 967 968<div class="node"> 969<p><hr> 970<a name="ntpd-Bugs"></a>Next: <a rel="next" accesskey="n" href="#ntpd-Notes">ntpd Notes</a>, 971Previous: <a rel="previous" accesskey="p" href="#ntpd-See-Also">ntpd See Also</a>, 972Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 973<br> 974</div> 975 976<h4 class="subsection">ntpd Bugs</h4> 977 978<div class="node"> 979<p><hr> 980<a name="ntpd-Notes"></a>Previous: <a rel="previous" accesskey="p" href="#ntpd-Bugs">ntpd Bugs</a>, 981Up: <a rel="up" accesskey="u" href="#ntpd-Invocation">ntpd Invocation</a> 982<br> 983</div> 984 985<h4 class="subsection">ntpd Notes</h4> 986 987<div class="node"> 988<p><hr> 989<a name="Usage"></a> 990<br> 991</div> 992 993<!-- node-name, next, previous, up --> 994<h3 class="section">Usage</h3> 995 996