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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: <!-- node-name, next, previous, up -->
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: <!-- node-name, next, previous, up -->
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:
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