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ntp 4.2.6p5

1: <html lang="en"> 2: <head> 3: <title>Sntp User's Manual</title> 4: <meta http-equiv="Content-Type" content="text/html"> 5: <meta name="description" content="Sntp 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"></style> 20: </head> 21: <body> 22: <h1 class="settitle">Sntp User's Manual</h1> 23: <div class="node"> 24: <p><hr> 25: <a name="Top"></a>Next: <a rel="next" accesskey="n" href="#sntp-Description">sntp Description</a>, 26: Previous: <a rel="previous" accesskey="p" href="#dir">(dir)</a>, 27: Up: <a rel="up" accesskey="u" href="#dir">(dir)</a> 28: <br> 29: </div> 30: 31: <h2 class="unnumbered">Simple Network Time Protocol User Manual</h2> 32: 33: <p>This document describes the use of the NTP Project's <code>sntp</code> program, 34: that can be used to query a Network Time Protocol (NTP) server and 35: display the time offset of the system clock relative to the server 36: clock. Run as root, it can correct the system clock to this offset as 37: well. It can be run as an interactive command or from a cron job. 38: 39: <p>This document applies to version 4.2.6p5 of <code>sntp</code>. 40: 41: <p>The program implements the SNTP protocol as defined by RFC 5905, the NTPv4 42: IETF specification. 43: 44: <div class="shortcontents"> 45: <h2>Short Contents</h2> 46: <ul> 47: <a href="#Top">Simple Network Time Protocol User Manual</a> 48: </ul> 49: </div> 50: 51: <ul class="menu"> 52: <li><a accesskey="1" href="#sntp-Description">sntp Description</a>: Description 53: <li><a accesskey="2" href="#sntp-Invocation">sntp Invocation</a>: Invoking sntp 54: <li><a accesskey="3" href="#Usage">Usage</a>: Usage 55: </ul> 56: 57: <div class="node"> 58: <p><hr> 59: <a name="sntp-Description"></a> 60: <br> 61: </div> 62: 63:  64: <h3 class="section">Description</h3> 65: 66: <p>By default, <code>sntp</code> writes the local data and time (i.e., not UTC) to the 67: standard output in the format: 68: 69: <pre class="example"> 1996 Oct 15 20:17:25.123 +4.567 +/- 0.089 secs 70: </pre> 71: <p>where the +4.567 +/- 0.089 secs indicates the time offset and 72: error bound of the system clock relative to the server clock. 73: 74: <div class="node"> 75: <p><hr> 76: <a name="sntp-Invocation"></a> 77: <br> 78: </div> 79: 80: <h3 class="section">Invoking sntp</h3> 81: 82: <p><a name="index-sntp-1"></a><a name="index-standard-Simple-Network-Time-Protocol-program-2"></a> 83: <code>sntp</code> 84: can be used as a SNTP client to query a NTP or SNTP server and either display 85: the time or set the local system's time (given suitable privilege). It can be 86: run as an interactive command or in a 87: <code>cron</code> 88: job. 89: 90: <p>NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol) 91: are defined and described by RFC 5905. 92: 93: <p class="indent">The default is to write the estimated correct local date and time (i.e. not 94: UTC) to the standard output in a format like 95: <pre class="example"> 1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 secs 96: </pre> 97: <p>where the 98: <pre class="example"> +4.567 +/- 0.089 secs 99: </pre> 100: <p>indicates the local clock is 4.567 seconds behind the correct time 101: (so 4.567 seconds must be added to the local clock to get it to be correct), 102: and the (local) time of 103: <code>1996-10-15 20:17:25.123</code> 104: can be converted to UTC time by adding 8 hours and 0 minutes, and 105: is believed to be correct to within 106: <code>+/- 0.089</code> 107: seconds. 108: 109: <p>This section was generated by <strong>AutoGen</strong>, 110: the aginfo template and the option descriptions for the <span class="command">sntp</span> program. It documents the <span class="command">sntp</span> usage text and option meanings. 111: 112: <p>This software is released under a specialized copyright license. 113: 114: <ul class="menu"> 115: <li><a accesskey="1" href="#sntp-usage">sntp usage</a>: sntp usage help (-?) 116: <li><a accesskey="2" href="#sntp-adjtime">sntp adjtime</a>: adjtime option (-j) 117: <li><a accesskey="3" href="#sntp-authentication">sntp authentication</a>: authentication option (-a) 118: <li><a accesskey="4" href="#sntp-broadcast">sntp broadcast</a>: broadcast option (-b) 119: <li><a accesskey="5" href="#sntp-ipv4">sntp ipv4</a>: ipv4 option (-4) 120: <li><a accesskey="6" href="#sntp-ipv6">sntp ipv6</a>: ipv6 option (-6) 121: <li><a accesskey="7" href="#sntp-keyfile">sntp keyfile</a>: keyfile option (-k) 122: <li><a accesskey="8" href="#sntp-kod">sntp kod</a>: kod option (-K) 123: <li><a accesskey="9" href="#sntp-logfile">sntp logfile</a>: logfile option (-l) 124: <li><a href="#sntp-normalverbose">sntp normalverbose</a>: normalverbose option (-d) 125: <li><a href="#sntp-settod">sntp settod</a>: settod option (-s) 126: <li><a href="#sntp-syslog">sntp syslog</a>: syslog option (-p) 127: <li><a href="#sntp-timeout">sntp timeout</a>: timeout option (-t) 128: </ul> 129: 130: <div class="node"> 131: <p><hr> 132: <a name="sntp-usage"></a>Next: <a rel="next" accesskey="n" href="#sntp-adjtime">sntp adjtime</a>, 133: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 134: <br> 135: </div> 136: 137: <h4 class="subsection">sntp usage help (-?)</h4> 138: 139: <p><a name="index-sntp-usage-3"></a> 140: This is the automatically generated usage text for sntp: 141: 142: <pre class="example">sntp - standard Simple Network Time Protocol program - Ver. 4.2.6p5 143: USAGE: sntp [ -<flag> [<val>] | --<name>[{=| }<val>] ]... \ 144: [ hostname-or-IP ...] 145: Flg Arg Option-Name Description 146: -4 no ipv4 Force IPv4 DNS name resolution 147: - prohibits these options: 148: ipv6 149: -6 no ipv6 Force IPv6 DNS name resolution 150: - prohibits these options: 151: ipv4 152: -d no normalverbose Normal verbose 153: -K Str kod KoD history filename 154: -p no syslog Logging with syslog 155: - prohibits these options: 156: logfile 157: -l Str logfile Log to specified logfile 158: - prohibits these options: 159: syslog 160: -s no settod Set (step) the time with settimeofday() 161: - prohibits these options: 162: adjtime 163: -j no adjtime Set (slew) the time with adjtime() 164: - prohibits these options: 165: settod 166: -b Str broadcast Use broadcasts to the address specified for synchronisation 167: -t Num timeout Specify the number of seconds to wait for broadcasts 168: -a Num authentication Enable authentication with the key auth-keynumber 169: -k Str keyfile Specify a keyfile. SNTP will look in this file for the key specified with -a 170: opt version Output version information and exit 171: -? no help Display extended usage information and exit 172: -! no more-help Extended usage information passed thru pager 173: -> opt save-opts Save the option state to a config file 174: -< Str load-opts Load options from a config file 175: - disabled as --no-load-opts 176: - may appear multiple times 177: 178: Options are specified by doubled hyphens and their name or by a single 179: hyphen and the flag character. 180: 181: 182: 183: The following option preset mechanisms are supported: 184: - reading file $HOME/.ntprc 185: - reading file ./.ntprc 186: - examining environment variables named SNTP_* 187: 188: sntp implements the Simple Network Time Protocol, and is used to query an 189: NTP or SNTP server and either display the time or set the local system's 190: time (given suitable privilege). 191: 192: It can be run interactively from the command line or as a cron job. 193: 194: NTP and SNTP are defined by RFC 5905, which obsoletes RFC 4330 and RFC 195: 1305. 196: 197: please send bug reports to: http://bugs.ntp.org, bugs@ntp.org 198: </pre> 199: <div class="node"> 200: <p><hr> 201: <a name="sntp-adjtime"></a>Next: <a rel="next" accesskey="n" href="#sntp-authentication">sntp authentication</a>, 202: Previous: <a rel="previous" accesskey="p" href="#sntp-usage">sntp usage</a>, 203: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 204: <br> 205: </div> 206: 207: <h4 class="subsection">adjtime option (-j)</h4> 208: 209: <p><a name="index-sntp_002dadjtime-4"></a> 210: This is the “set (slew) the time with adjtime()” option. 211: 212: <p>This option has some usage constraints. It: 213: <ul> 214: <li>must not appear in combination with any of the following options: 215: settod. 216: </ul> 217: 218: <div class="node"> 219: <p><hr> 220: <a name="sntp-authentication"></a>Next: <a rel="next" accesskey="n" href="#sntp-broadcast">sntp broadcast</a>, 221: Previous: <a rel="previous" accesskey="p" href="#sntp-adjtime">sntp adjtime</a>, 222: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 223: <br> 224: </div> 225: 226: <h4 class="subsection">authentication option (-a)</h4> 227: 228: <p><a name="index-sntp_002dauthentication-5"></a> 229: This is the “enable authentication with the key auth-keynumber” option. 230: This option enables authentication using the key specified in this option's argument. 231: The argument of this option is the keyid, a number specified in the keyfile as this 232: key's identifier. See the keyfile option (-k) for more details. 233: 234: <div class="node"> 235: <p><hr> 236: <a name="sntp-broadcast"></a>Next: <a rel="next" accesskey="n" href="#sntp-ipv4">sntp ipv4</a>, 237: Previous: <a rel="previous" accesskey="p" href="#sntp-authentication">sntp authentication</a>, 238: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 239: <br> 240: </div> 241: 242: <h4 class="subsection">broadcast option (-b)</h4> 243: 244: <p><a name="index-sntp_002dbroadcast-6"></a> 245: This is the “use broadcasts to the address specified for synchronisation” option. 246: If specified SNTP will listen to the specified broadcast address 247: for NTP broadcasts. The default maximum wait time, 248: 68 seconds, can be modified with -t. 249: 250: <div class="node"> 251: <p><hr> 252: <a name="sntp-ipv4"></a>Next: <a rel="next" accesskey="n" href="#sntp-ipv6">sntp ipv6</a>, 253: Previous: <a rel="previous" accesskey="p" href="#sntp-broadcast">sntp broadcast</a>, 254: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 255: <br> 256: </div> 257: 258: <h4 class="subsection">ipv4 option (-4)</h4> 259: 260: <p><a name="index-sntp_002dipv4-7"></a> 261: This is the “force ipv4 dns name resolution” option. 262: 263: <p>This option has some usage constraints. It: 264: <ul> 265: <li>must not appear in combination with any of the following options: 266: ipv6. 267: </ul> 268: 269: <p>Force DNS resolution of the following host names on the command line 270: to the IPv4 namespace. 271: 272: <div class="node"> 273: <p><hr> 274: <a name="sntp-ipv6"></a>Next: <a rel="next" accesskey="n" href="#sntp-keyfile">sntp keyfile</a>, 275: Previous: <a rel="previous" accesskey="p" href="#sntp-ipv4">sntp ipv4</a>, 276: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 277: <br> 278: </div> 279: 280: <h4 class="subsection">ipv6 option (-6)</h4> 281: 282: <p><a name="index-sntp_002dipv6-8"></a> 283: This is the “force ipv6 dns name resolution” option. 284: 285: <p>This option has some usage constraints. It: 286: <ul> 287: <li>must not appear in combination with any of the following options: 288: ipv4. 289: </ul> 290: 291: <p>Force DNS resolution of the following host names on the command line 292: to the IPv6 namespace. 293: 294: <div class="node"> 295: <p><hr> 296: <a name="sntp-keyfile"></a>Next: <a rel="next" accesskey="n" href="#sntp-kod">sntp kod</a>, 297: Previous: <a rel="previous" accesskey="p" href="#sntp-ipv6">sntp ipv6</a>, 298: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 299: <br> 300: </div> 301: 302: <h4 class="subsection">keyfile option (-k)</h4> 303: 304: <p><a name="index-sntp_002dkeyfile-9"></a> 305: This is the “specify a keyfile. sntp will look in this file for the key specified with -a” option. 306: This option specifies the keyfile. SNTP will search for the key specified with -a keyno in this 307: file. Key files follow the following format: 308: 309: <p>keyid keytype key 310: 311: <p>Where keyid is a number identifying this key 312: keytype is one of the follow: 313: S Key in 64 Bit hexadecimal number as specified in in the DES specification. 314: N Key in 64 Bit hexadecimal number as specified in the NTP standard. 315: A Key in a 1-to-8 character ASCII string. 316: M Key in a 1-to-8 character ASCII string using the MD5 authentication scheme. 317: 318: <p>For more information see ntp.keys(5). 319: 320: <div class="node"> 321: <p><hr> 322: <a name="sntp-kod"></a>Next: <a rel="next" accesskey="n" href="#sntp-logfile">sntp logfile</a>, 323: Previous: <a rel="previous" accesskey="p" href="#sntp-keyfile">sntp keyfile</a>, 324: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 325: <br> 326: </div> 327: 328: <h4 class="subsection">kod option (-K)</h4> 329: 330: <p><a name="index-sntp_002dkod-10"></a> 331: This is the “kod history filename” option. 332: Specifies the filename to be used to persist the history of KoD 333: responses received from servers. The default is 334: /var/db/ntp-kod. 335: 336: <div class="node"> 337: <p><hr> 338: <a name="sntp-logfile"></a>Next: <a rel="next" accesskey="n" href="#sntp-normalverbose">sntp normalverbose</a>, 339: Previous: <a rel="previous" accesskey="p" href="#sntp-kod">sntp kod</a>, 340: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 341: <br> 342: </div> 343: 344: <h4 class="subsection">logfile option (-l)</h4> 345: 346: <p><a name="index-sntp_002dlogfile-11"></a> 347: This is the “log to specified logfile” option. 348: 349: <p>This option has some usage constraints. It: 350: <ul> 351: <li>must not appear in combination with any of the following options: 352: syslog. 353: </ul> 354: 355: <p>This option causes the client to write log messages to the specified 356: logfile. 357: 358: <div class="node"> 359: <p><hr> 360: <a name="sntp-normalverbose"></a>Next: <a rel="next" accesskey="n" href="#sntp-settod">sntp settod</a>, 361: Previous: <a rel="previous" accesskey="p" href="#sntp-logfile">sntp logfile</a>, 362: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 363: <br> 364: </div> 365: 366: <h4 class="subsection">normalverbose option (-d)</h4> 367: 368: <p><a name="index-sntp_002dnormalverbose-12"></a> 369: This is the “normal verbose” option. 370: Diagnostic messages for non-fatal errors and a limited amount of 371: tracing should be written to standard error. Fatal ones always 372: produce a diagnostic. This option should be set when there is a 373: suspected problem with the server, network or the source. 374: 375: <div class="node"> 376: <p><hr> 377: <a name="sntp-settod"></a>Next: <a rel="next" accesskey="n" href="#sntp-syslog">sntp syslog</a>, 378: Previous: <a rel="previous" accesskey="p" href="#sntp-normalverbose">sntp normalverbose</a>, 379: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 380: <br> 381: </div> 382: 383: <h4 class="subsection">settod option (-s)</h4> 384: 385: <p><a name="index-sntp_002dsettod-13"></a> 386: This is the “set (step) the time with settimeofday()” option. 387: 388: <p>This option has some usage constraints. It: 389: <ul> 390: <li>must not appear in combination with any of the following options: 391: adjtime. 392: </ul> 393: 394: <div class="node"> 395: <p><hr> 396: <a name="sntp-syslog"></a>Next: <a rel="next" accesskey="n" href="#sntp-timeout">sntp timeout</a>, 397: Previous: <a rel="previous" accesskey="p" href="#sntp-settod">sntp settod</a>, 398: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 399: <br> 400: </div> 401: 402: <h4 class="subsection">syslog option (-p)</h4> 403: 404: <p><a name="index-sntp_002dsyslog-14"></a> 405: This is the “logging with syslog” option. 406: 407: <p>This option has some usage constraints. It: 408: <ul> 409: <li>must not appear in combination with any of the following options: 410: logfile. 411: </ul> 412: 413: <p>When this option is set all logging will be done using syslog. 414: 415: <div class="node"> 416: <p><hr> 417: <a name="sntp-timeout"></a>Previous: <a rel="previous" accesskey="p" href="#sntp-syslog">sntp syslog</a>, 418: Up: <a rel="up" accesskey="u" href="#sntp-Invocation">sntp Invocation</a> 419: <br> 420: </div> 421: 422: <h4 class="subsection">timeout option (-t)</h4> 423: 424: <p><a name="index-sntp_002dtimeout-15"></a> 425: This is the “specify the number of seconds to wait for broadcasts” option. 426: When waiting for a broadcast packet SNTP will wait the number 427: of seconds specified before giving up. Default 68 seconds. 428: 429: <div class="node"> 430: <p><hr> 431: <a name="Usage"></a> 432: <br> 433: </div> 434: 435:  436: <h3 class="section">Usage</h3> 437: 438: <p>The simplest use of this program is as an unprivileged command to 439: check the current time, offset, and error in the local clock. 440: For example: 441: 442: <pre class="example"> sntp ntpserver.somewhere 443: </pre> 444: <p>With suitable privilege, it can be run as a command or in a 445: <code>crom</code> job to reset the local clock from a reliable server, like 446: the <code>ntpdate</code> and <code>rdate</code> commands. 447: For example: 448: 449: <pre class="example"> sntp -a ntpserver.somewhere 450: </pre> 451: </body></html> 452: