/contrib/ntp/sntp/sntp-opts.def

  1/* -*- Mode: Text -*- */
  2
  3autogen definitions options;
  4
  5#include autogen-version.def
  6
  7copyright = {
  8    date  = "1970-2006";
  9    owner = "ntp.org";
 10    eaddr = "http://bugs.ntp.org, bugs@ntp.org";
 11    type  = note;
 12    text  = `cat COPYRIGHT`;
 13};
 14
 15
 16prog-name      = "sntp";
 17prog-title     = "standard SNTP program";
 18homerc         =  $HOME, ".";
 19long-opts;
 20
 21config-header  = "config.h";
 22
 23#ifndef __windows__
 24rcfile         = ".ntprc";
 25#else
 26rcfile         = "ntp.ini";
 27#endif
 28
 29environrc;
 30
 31#include version.def
 32
 33test-main;
 34
 35flag = {
 36    name      = ipv4;
 37    value     = 4;
 38    equivalence = ipv4;
 39    descrip   = "Force IPv4 DNS name resolution";
 40    doc = <<-  _EndOfDoc_
 41	Force DNS resolution of following host names on the command line
 42	to the IPv4 namespace.
 43	_EndOfDoc_;
 44};
 45
 46flag = {
 47    name      = ipv6;
 48    value     = 6;
 49    equivalence = ipv4;
 50    descrip   = "Force IPv6 DNS name resolution";
 51    doc = <<-  _EndOfDoc_
 52	Force DNS resolution of following host names on the command line
 53	to the IPv6 namespace.
 54	_EndOfDoc_;
 55};
 56
 57flag = {
 58    name      = unprivport;
 59    value     = u;
 60    descrip   = "Use an unprivileged port";
 61    doc = <<-  _EndOfDoc_
 62	Use an unprivilegded UDP port for our queries.
 63	_EndOfDoc_;
 64};
 65
 66flag = {
 67    name      = normalverbose;
 68    value     = v;
 69    flags-cant = extraverbose, megaverbose;
 70    descrip   = "Slightly verbose";
 71    doc = <<-  _EndOfDoc_
 72	Diagnostic messages for non-fatal errors and a limited amount of
 73	tracing should be written to standard error.  Fatal ones always
 74	produce a diagnostic.  This option should be set when there is a
 75	suspected problem with the server, network or the source.
 76	_EndOfDoc_;
 77};
 78
 79flag = {
 80    name      = extraverbose;
 81    value     = V;
 82    flags-cant = normalverbose, megaverbose;
 83    descrip   = "Extra verbose";
 84    doc = <<-  _EndOfDoc_
 85	Produce more and less comprehensible output, mainly for investigating
 86	problems with apparently inconsistent timestamps.  This option should
 87	be set when the program fails with a message indicating that is the
 88	trouble.
 89	_EndOfDoc_;
 90};
 91
 92flag = {
 93    name      = megaverbose;
 94    value     = W;
 95    flags-cant = normalverbose, extraverbose;
 96    descrip   = "Mega verbose";
 97    doc = <<-  _EndOfDoc_
 98	Very verbose debugging output that will interfere with the timing
 99	when writing to the terminal (because of line buffered output from C).
100	Note that the times produced by this are the corrections needed, and
101	not the error in the local clock.  This option should be set only when
102	debugging the source.
103	_EndOfDoc_;
104};
105
106flag = {
107    name      = settimeofday;
108    value     = r;
109    flags-cant = adjtime;
110    descrip   = "Set (step) the time with settimeofday()";
111    doc = <<-  _EndOfDoc_
112	_EndOfDoc_;
113};
114
115flag = {
116    name      = adjtime;
117    value     = a;
118    flags-cant = settimeofday;
119    descrip   = "Set (slew) the time with adjtime()";
120    doc = <<-  _EndOfDoc_
121	_EndOfDoc_;
122};
123
124detail = <<-  _END_DETAIL
125.I sntp
126can be used as a SNTP client to query a NTP or SNTP server and either display
127the time or set the local system's time (given suitable privilege).  It can be
128run as an interactive command or in a
129.I cron
130job.
131NTP is the Network Time Protocol (RFC 1305) and SNTP is the
132Simple Network Time Protocol (RFC 2030, which supersedes RFC 1769).
133	_END_DETAIL;
134
135prog-man-descrip = <<-  _END_PROG_MAN_DESCRIP
136.I sntp
137can be used as a SNTP client to query a NTP or SNTP server and either display
138the time or set the local system's time (given suitable privilege).  It can be
139run as an interactive command or in a
140.I cron
141job.
142NTP is the Network Time Protocol (RFC 1305) and SNTP is the
143Simple Network Time Protocol (RFC 2030, which supersedes RFC 1769).
144.SS Options
145.PP
146.I sntp
147recognizes the following options:
148.TP
149.B \-v
150indicates that diagnostic messages for non-fatal errors and a limited amount of
151tracing should be written to standard error.  Fatal ones always produce a
152diagnostic.  This option should be set when there is a suspected problem with
153the server, network or the source.
154.TP
155.B \-V
156requests more and less comprehensible output, mainly for investigating problems
157with apparently inconsistent timestamps.  This option should be set when the
158program fails with a message indicating that is the trouble.
159.TP
160.B \-W
161requests very verbose debugging output, and will interfere with the timing
162when writing to the terminal (because of line buffered output from C).  Note
163that the times produced by this are the corrections needed, and not the error
164in the local clock.  This option should be set only when debugging the source.
165.TP
166.B \-q
167indicates that it should query a daemon save file being maintained by it.
168This needs no privilege and will change neither the save file nor the clock.
169.PP
170The default is that it should behave as a client, and the following options
171are then relevant:
172.TP
173.B \-r
174indicates that the system clock should be reset by
175.IR settimeofday .
176Naturally, this will work only if the user has enough privilege.
177.TP
178.B \-a
179indicates that the system clock should be reset by
180.IR adjtime .
181Naturally, this will work only if the user has enough privilege.
182.PP
183The default is to write the estimated correct local date and time (i.e. not
184UTC) to the standard output in a format like
185.BR "'1996 Oct 15 20:17:25.123 + 4.567 +/- 0.089 secs'" ,
186where the
187.B "'+ 4.567 +/- 0.089 secs'"
188indicates the estimated error in the time on the local system.
189.TP
190.BI \-l " lockfile"
191sets the name of the lock file to ensure that there is only
192one copy of
193.I sntp
194running at once.  The default is installation-dependent, but will usually be
195.IR /etc/sntp.pid .
196.TP
197.BI \-e " minerr"
198sets the maximum ignorable variation between the clocks to
199.IR minerr .
200Acceptable values are from 0.001 to 1, and the default is 0.1 if a NTP host is
201is specified and 0.5 otherwise.
202.TP
203.BI \-E " maxerr"
204sets the maximum value of various delays that are deemed acceptable to
205.IR maxerr .
206Acceptable values are from 1 to 60, and the default is 5.  It should sometimes
207be increased if there are problems with the network, NTP server or system
208clock, but take care.
209.TP
210.BI \-P  " prompt"
211sets the maximum clock change that will be made automatically to
212.IR maxerr .
213Acceptable values are from 1 to 3600 or
214.IR no ,
215and the default is 30.  If the program is being run interactively in ordinary
216client mode, and the system clock is to be changed, larger corrections will
217prompt the user for confirmation.  Specifying
218.I no
219will disable this and the correction will be made regardless.
220.TP
221.BI \-c " count"
222sets the maximum number of NTP packets required to
223.IR count .
224Acceptable values are from 1 to 25 if a NTP host is specified and from 5 to 25
225otherwise, and the default is 5.  If the maximum isn't enough, the system needs
226a better consistency algorithm than this program uses.
227.TP
228.BI \-d " delay"
229sets a rough limit on the total running time to
230.I delay
231seconds.  Acceptable values are from 1 to 3600, and the default is 15 if a NTP
232host is specified and 300 otherwise.
233.TP
234.B -4
235force IPv4 DNS resolution.
236.TP
237.B -6
238force IPv6 DNS resolution.
239.PP
240.B address(es)
241are the DNS names or IP numbers of hosts to use for the challenge and response
242protocol; if no names are given, the program waits for broadcasts.  Polling a
243server is vastly more reliable than listening to broadcasts.  Note that a
244single component numeric address is not allowed, to avoid ambiguities.  If
245more than one name is give, they will be used in a round-robin fashion.
246.PP
247Constraints:
248.IP
249.B minerr
250must be less than
251.B maxerr
252which must be less than
253.B delay
254(or, if a NTP host is not specified
255.BR delay / count "),"
256and
257.B count
258must be less than half of
259.BR delay .
260.IP
261In update mode,
262.B maxerr
263must be less than
264.BR prompt.
265.PP
266Note that none of the above values are closely linked to the limits described
267in the NTP protocol (RFC 1305).
268.SH USAGE
269The simplest use of this program is as an unprivileged command to check the
270current time and error in the local clock.  For example:
271.IP
272.B sntp ntpserver.somewhere
273.PP
274With suitable privilege, it can be run as a command or in a
275.I cron
276job to reset the local clock from a reliable server, like the
277.I ntpdate
278and
279.I rdate
280commands.  For example:
281.IP
282.B sntp -a ntpserver.somewhere
283.PP
284More information on how to use this utility is given in the
285.I README
286file in the distribution.  In particular, this
287.I man
288page does not describe how to set it up as a server, which needs special care
289to avoid propagating misinformation.
290.SH RETURN VALUE
291When used as a client in non-daemon mode, the program returns a zero exit
292status for success, and a non-zero one otherwise. When used as a daemon
293(either client or server), it does not return except after a serious error.
294.SH BUGS
295The program implements the SNTP protocol, and does not provide all NTP 
296facilities.  In particular, it contains no checks against any form of spoofing.
297If this is a serious concern, some network security mechanism (like a firewall
298or even just
299.IR tcpwrappers )
300should be installed.
301.PP
302There are some errors, ambiguities and inconsistencies in the RFCs, and this
303code may not interwork with all other NTP implementations.  Any unreasonable
304restrictions should be reported as bugs to whoever is responsible.  It may
305be difficult to find out who that is.
306.PP
307The program will stop as soon as it feels that things have got out of control.
308In client daemon mode, it will usually fail during an extended period of
309network or server inaccessibility or excessively slow performance, or when the
310local clock is reset by another process.  It will then need restarting
311manually.  Experienced system administrators can write a shell script, a
312.I cron
313job or put it in
314.IR inittab ,
315to do this automatically.
316.PP
317The error cannot be estimated reliably with broadcast packets or for the drift
318in daemon mode (even with client-server packets), and the guess made by the
319program may be wrong (possibly even very wrong).  If this is a problem, then
320setting the
321.B \-c
322option to a larger value may help.  Or it may not.
323.SH AUTHOR
324.I sntp
325was developed by N.M. Maclaren of the University of Cambridge Computing
326Service.
327	_END_PROG_MAN_DESCRIP;