1SNTP(8) Programmer's Manual SNTP(8)
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6 sntp - standard SNTP program
7
9 sntp [-flag [value]]... [--opt-name [[=| ]value]]...
10 hostname-or-IP ...
11
13 This manual page briefly documents the sntp command. sntp can be used
14 as a SNTP client to query a NTP or SNTP server and either display the
15 time or set the local system's time (given suitable privilege). It can
16 be run as an interactive command or in a cron job.
17 NTP (the Network Time Protocol) and SNTP (the Simple Network Time Pro‐
19 tocol) are defined and described by RFC 5905.
20 The default is to write the estimated correct local date and time (i.e.
23 not UTC) to the standard output in a format like '1996 Oct 15
24 20:17:25.123 +4.567 +/- 0.089 secs', where the '+4.567 +/- 0.089 secs'
25 indicates the local clock is 4.567 seconds behind the correct time (so
26 4.567 seconds must be added to the local clock to get it to be cor‐
27 rect), and the time of is believed to be correct to within +/- 0.089
28 seconds.
29
31 -4, --ipv4
32 Force IPv4 DNS name resolution. This option must not appear in
33 combination with any of the following options: ipv6.
34 Force DNS resolution of following host names on the command line
36 to the IPv4 namespace.
37 -6, --ipv6
39 Force IPv6 DNS name resolution. This option must not appear in
40 combination with any of the following options: ipv4.
41 Force DNS resolution of following host names on the command line
43 to the IPv6 namespace.
44 -d, --normalverbose
46 Normal verbose.
47 Diagnostic messages for non-fatal errors and a limited amount of
49 tracing should be written to standard error. Fatal ones always
50 produce a diagnostic. This option should be set when there is a
51 suspected problem with the server, network or the source.
52 -K file-name, --kod=file-name
54 KoD history filename.
55 Modifies the filename to be used to persist the history of KoD
57 responses received from servers. The default is
58 /var/lib/ntp/sntp-kod.
59 -p, --syslog
61 Logging with syslog. This option must not appear in combination
62 with any of the following options: filelog.
63 When this option is set all logging will be done using syslog.
65 -l file-name, --filelog=file-name
67 Log to specified logfile. This option must not appear in combi‐
68 nation with any of the following options: syslog.
69 This option causes the client to write log messages to the spec‐
71 ified logfile.
72 -s, --settod
74 Set (step) the time with settimeofday(). This option must not
75 appear in combination with any of the following options: adj‐
76 time.
77 -j, --adjtime
81 Set (slew) the time with adjtime(). This option must not appear
82 in combination with any of the following options: settod.
83 -b broadcast-address, --broadcast=broadcast-address
87 Use broadcasts to the address specified for synchronisation.
88 If specified SNTP will listen to the specified broadcast address
90 for NTP broadcasts. The default maximum wait time, 68 seconds,
91 can be modified with -t.
92 -t seconds, --timeout=seconds
94 Specify the number of seconds to wait for broadcasts. This
95 option takes an integer number as its argument. The default
96 seconds for this option is:
97 68
98 When waiting for a broadcast packet SNTP will wait the number of
100 seconds specified before giving up. Default 68 seconds.
101 -a auth-keynumber, --authentication=auth-keynumber
103 Enable authentication with the key auth-keynumber. This option
104 takes an integer number as its argument.
105 This option enables authentication using the key specified in
107 this option's argument. The argument of this option is the
108 keyid, a number specified in the keyfile as this key's identi‐
109 fier. See the keyfile option (-k) for more details.
110 -k file-name, --keyfile=file-name
112 Specify a keyfile. SNTP will look in this file for the key spec‐
113 ified with -a.
114 This option specifies the keyfile. SNTP will search for the key
116 specified with -a keyno in this file. Key files follow the fol‐
117 lowing format:
118 keyid keytype key
120 Where keyid is a number identifying this key keytype is one
122 of the follow: S Key in 64 Bit hexadecimal number as specified
123 in in the DES specification. N Key in 64 Bit hexadecimal num‐
124 ber as specified in the NTP standard. A Key in a 1-to-8 char‐
125 acter ASCII string. M Key in a 1-to-8 character ASCII string
126 using the MD5 authentication scheme.
127 For more information see ntp.keys(5).
129 -?, --help
131 Display extended usage information and exit.
132 -!, --more-help
134 Extended usage information passed thru pager.
135 -> [rcfile], --save-opts[=rcfile]
137 Save the option state to rcfile. The default is the last con‐
138 figuration file listed in the OPTION PRESETS section, below.
139 -< rcfile, --load-opts=rcfile, --no-load-opts
141 Load options from rcfile. The no-load-opts form will disable
142 the loading of earlier RC/INI files. --no-load-opts is handled
143 early, out of order.
144 - [{v|c|n}], --version[={v|c|n}]
146 Output version of program and exit. The default mode is `v', a
147 simple version. The `c' mode will print copyright information
148 and `n' will print the full copyright notice.
149
151 Any option that is not marked as not presettable may be preset by load‐
152 ing values from configuration ("RC" or ".INI") file(s) and values from
153 environment variables named:
154 SNTP_<option-name> or SNTP
155 The environmental presets take precedence (are processed later than)
156 the configuration files. The homerc files are "$HOME", and ".". If
157 any of these are directories, then the file .ntprc is searched for
158 within those directories.
159
161 The simplest use of this program is as an unprivileged command to check
162 the current time and error in the local clock. For example:
163 sntp ntpserver.somewhere
165 With suitable privilege, it can be run as a command or in a cron job to
167 reset the local clock from a reliable server, like the ntpdate and
168 rdate commands. For example:
169 sntp -a ntpserver.somewhere
171
173 The program returns a zero exit status for success, and a non-zero one
174 otherwise.
175
177 Please report bugs to http://bugs.ntp.org .
178
180 David L. Mills and/or others
181 Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org
182 see html/copyright.html
185 This manual page was AutoGen-erated from the sntp option definitions.
187( 4.2.6p3-RC10) 2010-11-14 SNTP(8)