1SNTP(8) Programmer's Manual SNTP(8)
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6 sntp - standard Simple Network Time Protocol 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 '1996-10-15
24 20:17:25.123 (+0800) +4.567 +/- 0.089 secs', where the '(+0800)' means
25 that to get to UTC from the reported local time one must add 8 hours
26 and 0 minutes, and the '+4.567 +/- 0.089 secs' indicates the local
27 clock is 4.567 seconds behind the correct time (so 4.567 seconds must
28 be added to the local clock to get it to be correct), and the time of
29 is believed to be correct to within +/- 0.089 seconds.
30
32 -4, --ipv4
33 Force IPv4 DNS name resolution. This option must not appear in
34 combination with any of the following options: ipv6.
35 Force DNS resolution of the following host names on the command
37 line to the IPv4 namespace.
38 -6, --ipv6
40 Force IPv6 DNS name resolution. This option must not appear in
41 combination with any of the following options: ipv4.
42 Force DNS resolution of the following host names on the command
44 line to the IPv6 namespace.
45 -d, --normalverbose
47 Normal verbose.
48 Diagnostic messages for non-fatal errors and a limited amount of
50 tracing should be written to standard error. Fatal ones always
51 produce a diagnostic. This option should be set when there is a
52 suspected problem with the server, network or the source.
53 -K file-name, --kod=file-name
55 KoD history filename.
56 Specifies the filename to be used to persist the history of KoD
58 responses received from servers. The default is
59 /var/lib/sntp/kod.
60 -p, --syslog
62 Logging with syslog. This option must not appear in combination
63 with any of the following options: logfile.
64 When this option is set all logging will be done using syslog.
66 -l file-name, --logfile=file-name
68 Log to specified logfile. This option must not appear in combi‐
69 nation with any of the following options: syslog.
70 This option causes the client to write log messages to the spec‐
72 ified logfile.
73 -s, --settod
75 Set (step) the time with settimeofday(). This option must not
76 appear in combination with any of the following options: adj‐
77 time.
78 -j, --adjtime
82 Set (slew) the time with adjtime(). This option must not appear
83 in combination with any of the following options: settod.
84 -b broadcast-address, --broadcast=broadcast-address
88 Use broadcasts to the address specified for synchronisation.
89 If specified SNTP will listen to the specified broadcast address
91 for NTP broadcasts. The default maximum wait time, 68 seconds,
92 can be modified with -t.
93 -t seconds, --timeout=seconds
95 Specify the number of seconds to wait for broadcasts. This
96 option takes an integer number as its argument. The default
97 seconds for this option is:
98 68
99 When waiting for a broadcast packet SNTP will wait the number of
101 seconds specified before giving up. Default 68 seconds.
102 -a auth-keynumber, --authentication=auth-keynumber
104 Enable authentication with the key auth-keynumber. This option
105 takes an integer number as its argument.
106 This option enables authentication using the key specified in
108 this option's argument. The argument of this option is the
109 keyid, a number specified in the keyfile as this key's identi‐
110 fier. See the keyfile option (-k) for more details.
111 -k file-name, --keyfile=file-name
113 Specify a keyfile. SNTP will look in this file for the key spec‐
114 ified with -a.
115 This option specifies the keyfile. SNTP will search for the key
117 specified with -a keyno in this file. Key files follow the fol‐
118 lowing format:
119 keyid keytype key
121 Where keyid is a number identifying this key keytype is one
123 of the follow: S Key in 64 Bit hexadecimal number as specified
124 in in the DES specification. N Key in 64 Bit hexadecimal num‐
125 ber as specified in the NTP standard. A Key in a 1-to-8 char‐
126 acter ASCII string. M Key in a 1-to-8 character ASCII string
127 using the MD5 authentication scheme.
128 For more information see ntp.keys(5).
130 -?, --help
132 Display extended usage information and exit.
133 -!, --more-help
135 Extended usage information passed thru pager.
136 -> [rcfile], --save-opts[=rcfile]
138 Save the option state to rcfile. The default is the last con‐
139 figuration file listed in the OPTION PRESETS section, below.
140 -< rcfile, --load-opts=rcfile, --no-load-opts
142 Load options from rcfile. The no-load-opts form will disable
143 the loading of earlier RC/INI files. --no-load-opts is handled
144 early, out of order.
145 - [{v|c|n}], --version[={v|c|n}]
147 Output version of program and exit. The default mode is `v', a
148 simple version. The `c' mode will print copyright information
149 and `n' will print the full copyright notice.
150
152 Any option that is not marked as not presettable may be preset by load‐
153 ing values from configuration ("RC" or ".INI") file(s) and values from
154 environment variables named:
155 SNTP_<option-name> or SNTP
156 The environmental presets take precedence (are processed later than)
157 the configuration files. The homerc files are "$HOME", and ".". If
158 any of these are directories, then the file .ntprc is searched for
159 within those directories.
160
162 The simplest use of this program is as an unprivileged command to check
163 the current time and error in the local clock. For example:
164 sntp ntpserver.somewhere
166 With suitable privilege, it can be run as a command or in a cron job to
168 reset the local clock from a reliable server, like the ntpdate and
169 rdate commands. For example:
170 sntp -a ntpserver.somewhere
172
174 The program returns a zero exit status for success, and a non-zero one
175 otherwise.
176
178 Please report bugs to http://bugs.ntp.org .
179
181 David L. Mills and/or others
182 Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org
183 see html/copyright.html
186 This manual page was AutoGen-erated from the sntp option definitions.
189( 4.2.6p5) 2011-12-24 SNTP(8)