1 .de1 NOP 2 . it 1 an-trap 3 . if \\n[.$] \,\\$*\/ 4 .. 5 .ie t \ 6 .ds B-Font [CB] 7 .ds I-Font [CI] 8 .ds R-Font [CR] 9 .el \ 10 .ds B-Font B 11 .ds I-Font I 12 .ds R-Font R 13 .TH sntp 1sntpman "25 May 2024" "4.2.8p18" "User Commands" 14 .\" 15 .\" EDIT THIS FILE WITH CAUTION (in-mem file) 16 .\" 17 .\" It has been AutoGen-ed May 25, 2024 at 12:02:30 AM by AutoGen 5.18.16 18 .\" From the definitions sntp-opts.def 19 .\" and the template file agman-cmd.tpl 20 .SH NAME 21 \f\*[B-Font]sntp\fP 22 \- standard Simple Network Time Protocol client program 23 .SH SYNOPSIS 24 \f\*[B-Font]sntp\fP 25 .\" Mixture of short (flag) options and long options 26 [\f\*[B-Font]\-flags\f[]] 27 [\f\*[B-Font]\-flag\f[] [\f\*[I-Font]value\f[]]] 28 [\f\*[B-Font]\-\-option-name\f[][[=| ]\f\*[I-Font]value\f[]]] 29 [ hostname-or-IP ...] 30 .sp \n(Ppu 31 .ne 2 32 33 .SH DESCRIPTION 34 \f\*[B-Font]sntp\fP 35 can be used as an SNTP client to query a NTP or SNTP server and either display 36 the time or set the local system's time (given suitable privilege). It can be 37 run as an interactive command or from a 38 \f\*[B-Font]cron\f[] 39 job. 40 NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol) 41 are defined and described by RFC 5905. 42 .sp \n(Ppu 43 .ne 2 44 45 The default is to write the estimated correct local date and time (i.e. not 46 UTC) to the standard output in a format like: 47 \f\*[B-Font]'1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 [host] IP sN'\f[] 48 where the 49 \f\*[B-Font]'(+0800)'\f[] 50 means that to get to UTC from the reported local time one must 51 add 8 hours and 0 minutes, 52 the 53 \f\*[B-Font]'+4.567'\f[] 54 indicates the local clock is 4.567 seconds behind the correct time 55 (so 4.567 seconds must be added to the local clock to get it to be correct). 56 Note that the number of decimals printed for this value will change 57 based on the reported precision of the server. 58 \f\*[B-Font]'+/- 0.089'\f[] 59 is the reported 60 \fIsynchronization\f[] \fIdistance\f[] 61 (in seconds), which represents the maximum error due to all causes. 62 If the server does not report valid data needed to calculate the 63 synchronization distance, this will be reported as 64 \f\*[B-Font]'+/- ?'\f[]. 65 If the 66 \fIhost\f[] 67 is different from the 68 \fIIP\f[], 69 both will be displayed. 70 Otherwise, only the 71 \fIIP\f[] 72 is displayed. 73 Finally, the 74 \fIstratum\f[] 75 of the host is reported 76 and the leap indicator is decoded and displayed. 77 .SH "OPTIONS" 78 .TP 79 .NOP \f\*[B-Font]\-4\f[], \f\*[B-Font]\-\-ipv4\f[] 80 Force IPv4 DNS name resolution. 81 This option must not appear in combination with any of the following options: 82 ipv6. 83 .sp 84 Force DNS resolution of the following host names on the command line 85 to the IPv4 namespace. 86 .TP 87 .NOP \f\*[B-Font]\-6\f[], \f\*[B-Font]\-\-ipv6\f[] 88 Force IPv6 DNS name resolution. 89 This option must not appear in combination with any of the following options: 90 ipv4. 91 .sp 92 Force DNS resolution of the following host names on the command line 93 to the IPv6 namespace. 94 .TP 95 .NOP \f\*[B-Font]\-a\f[] \f\*[I-Font]auth\-keynumber\f[], \f\*[B-Font]\-\-authentication\f[]=\f\*[I-Font]auth\-keynumber\f[] 96 Enable authentication with the key \fBauth-keynumber\fP. 97 This option takes an integer number as its argument. 98 .sp 99 Enable authentication using the key specified in this option's 100 argument. The argument of this option is the \fBkeyid\fP, a 101 number specified in the \fBkeyfile\fP as this key's identifier. 102 See the \fBkeyfile\fP option (\fB-k\fP) for more details. 103 .TP 104 .NOP \f\*[B-Font]\-b\f[] \f\*[I-Font]broadcast\-address\f[], \f\*[B-Font]\-\-broadcast\f[]=\f\*[I-Font]broadcast\-address\f[] 105 Listen to the address specified for broadcast time sync. 106 This option may appear an unlimited number of times. 107 .sp 108 If specified \fBsntp\fP will listen to the specified address 109 for NTP broadcasts. The default maximum wait time 110 can (and probably should) be modified with \fB-t\fP. 111 .TP 112 .NOP \f\*[B-Font]\-c\f[] \f\*[I-Font]host\-name\f[], \f\*[B-Font]\-\-concurrent\f[]=\f\*[I-Font]host\-name\f[] 113 Concurrently query all IPs returned for host-name. 114 This option may appear an unlimited number of times. 115 .sp 116 Requests from an NTP "client" to a "server" should never be sent 117 more rapidly than one every 2 seconds. By default, any IPs returned 118 as part of a DNS lookup are assumed to be for a single instance of 119 \fBntpd\fP, and therefore \fBsntp\fP will send queries to these IPs 120 one after another, with a 2-second gap in between each query. 121 .sp 122 The \fB-c\fP or \fB--concurrent\fP flag says that any IPs 123 returned for the DNS lookup of the supplied host-name are on 124 different machines, so we can send concurrent queries. 125 .TP 126 .NOP \f\*[B-Font]\-d\f[], \f\*[B-Font]\-\-debug\-level\f[] 127 Increase debug verbosity level. 128 This option may appear an unlimited number of times. 129 .sp 130 .TP 131 .NOP \f\*[B-Font]\-D\f[] \f\*[I-Font]number\f[], \f\*[B-Font]\-\-set\-debug\-level\f[]=\f\*[I-Font]number\f[] 132 Set the debug verbosity level. 133 This option may appear an unlimited number of times. 134 This option takes an integer number as its argument. 135 .sp 136 .TP 137 .NOP \f\*[B-Font]\-g\f[] \f\*[I-Font]milliseconds\f[], \f\*[B-Font]\-\-gap\f[]=\f\*[I-Font]milliseconds\f[] 138 The gap (in milliseconds) between time requests. 139 This option takes an integer number as its argument. 140 The default 141 \f\*[I-Font]milliseconds\f[] 142 for this option is: 143 .ti +4 144 50 145 .sp 146 Since we're only going to use the first valid response we get and 147 there is benefit to specifying a good number of servers to query, 148 separate the queries we send out by the specified number of 149 milliseconds. 150 .TP 151 .NOP \f\*[B-Font]\-K\f[] \f\*[I-Font]file\-name\f[], \f\*[B-Font]\-\-kod\f[]=\f\*[I-Font]file\-name\f[] 152 KoD history filename. 153 The default 154 \f\*[I-Font]file\-name\f[] 155 for this option is: 156 .ti +4 157 /var/db/ntp-kod 158 .sp 159 Specifies the filename to be used for the persistent history of KoD 160 responses received from servers. If the file does not exist, a 161 warning message will be displayed. The file will not be created. 162 .TP 163 .NOP \f\*[B-Font]\-k\f[] \f\*[I-Font]file\-name\f[], \f\*[B-Font]\-\-keyfile\f[]=\f\*[I-Font]file\-name\f[] 164 Look in this file for the key specified with \fB-a\fP. 165 The default 166 \f\*[I-Font]file\-name\f[] 167 for this option is: 168 .ti +4 169 /etc/ntp.keys 170 .sp 171 This option specifies the keyfile. 172 \fBsntp\fP will search for the key specified with \fB-a\fP 173 \fIkeyno\fP in this file. See \fBntp.keys(5)\fP for more 174 information. 175 .TP 176 .NOP \f\*[B-Font]\-l\f[] \f\*[I-Font]file\-name\f[], \f\*[B-Font]\-\-logfile\f[]=\f\*[I-Font]file\-name\f[] 177 Log to specified logfile. 178 .sp 179 This option causes the client to write log messages to the specified 180 \fIlogfile\fP. 181 .TP 182 .NOP \f\*[B-Font]\-M\f[] \f\*[I-Font]number\f[], \f\*[B-Font]\-\-steplimit\f[]=\f\*[I-Font]number\f[] 183 Adjustments less than \fBsteplimit\fP msec will be slewed. 184 This option takes an integer number as its argument. 185 The value of 186 \f\*[I-Font]number\f[] 187 is constrained to being: 188 .in +4 189 .nf 190 .na 191 greater than or equal to 0 192 .fi 193 .in -4 194 .sp 195 If the time adjustment is less than \fIsteplimit\fP milliseconds, 196 slew the amount using \fBadjtime(2)\fP. Otherwise, step the 197 correction using \fBsettimeofday(2)\fP. The default value is 0, 198 which means all adjustments will be stepped. This is a feature, as 199 different situations demand different values. 200 .TP 201 .NOP \f\*[B-Font]\-o\f[] \f\*[I-Font]number\f[], \f\*[B-Font]\-\-ntpversion\f[]=\f\*[I-Font]number\f[] 202 Send \fBint\fP as our NTP protocol version. 203 This option takes an integer number as its argument. 204 The value of 205 \f\*[I-Font]number\f[] 206 is constrained to being: 207 .in +4 208 .nf 209 .na 210 in the range 0 through 7 211 .fi 212 .in -4 213 The default 214 \f\*[I-Font]number\f[] 215 for this option is: 216 .ti +4 217 4 218 .sp 219 When sending requests to a remote server, tell them we are running 220 NTP protocol version \fIntpversion\fP . 221 .TP 222 .NOP \f\*[B-Font]\-r\f[], \f\*[B-Font]\-\-usereservedport\f[] 223 Use the NTP Reserved Port (port 123). 224 .sp 225 Use port 123, which is reserved for NTP, for our network 226 communications. 227 .TP 228 .NOP \f\*[B-Font]\-S\f[], \f\*[B-Font]\-\-step\f[] 229 OK to 'step' the time with \fBsettimeofday(2)\fP. 230 .sp 231 .TP 232 .NOP \f\*[B-Font]\-s\f[], \f\*[B-Font]\-\-slew\f[] 233 OK to 'slew' the time with \fBadjtime(2)\fP. 234 .sp 235 .TP 236 .NOP \f\*[B-Font]\-t\f[] \f\*[I-Font]seconds\f[], \f\*[B-Font]\-\-timeout\f[]=\f\*[I-Font]seconds\f[] 237 The number of seconds to wait for responses. 238 This option takes an integer number as its argument. 239 The default 240 \f\*[I-Font]seconds\f[] 241 for this option is: 242 .ti +4 243 5 244 .sp 245 When waiting for a reply, \fBsntp\fP will wait the number 246 of seconds specified before giving up. The default should be 247 more than enough for a unicast response. If \fBsntp\fP is 248 only waiting for a broadcast response a longer timeout is 249 likely needed. 250 .TP 251 .NOP \f\*[B-Font]\-\-wait\f[], \f\*[B-Font]\-\-no\-wait\f[] 252 Wait for pending replies (if not setting the time). 253 The \fIno\-wait\fP form will disable the option. 254 This option is enabled by default. 255 .sp 256 If we are not setting the time, wait for all pending responses. 257 .TP 258 .NOP \f\*[B-Font]\-\&?\f[], \f\*[B-Font]\-\-help\f[] 259 Display usage information and exit. 260 .TP 261 .NOP \f\*[B-Font]\-\&!\f[], \f\*[B-Font]\-\-more-help\f[] 262 Pass the extended usage information through a pager. 263 .TP 264 .NOP \f\*[B-Font]\->\f[] [\f\*[I-Font]cfgfile\f[]], \f\*[B-Font]\-\-save-opts\f[] [=\f\*[I-Font]cfgfile\f[]] 265 Save the option state to \fIcfgfile\fP. The default is the \fIlast\fP 266 configuration file listed in the \fBOPTION PRESETS\fP section, below. 267 The command will exit after updating the config file. 268 .TP 269 .NOP \f\*[B-Font]\-<\f[] \f\*[I-Font]cfgfile\f[], \f\*[B-Font]\-\-load-opts\f[]=\f\*[I-Font]cfgfile\f[], \f\*[B-Font]\-\-no-load-opts\f[] 270 Load options from \fIcfgfile\fP. 271 The \fIno-load-opts\fP form will disable the loading 272 of earlier config/rc/ini files. \fI\-\-no-load-opts\fP is handled early, 273 out of order. 274 .TP 275 .NOP \f\*[B-Font]\-\-version\f[] [{\f\*[I-Font]v|c|n\f[]}] 276 Output version of program and exit. The default mode is `v', a simple 277 version. The `c' mode will print copyright information and `n' will 278 print the full copyright notice. 279 .PP 280 .SH "OPTION PRESETS" 281 Any option that is not marked as \fInot presettable\fP may be preset 282 by loading values from configuration ("RC" or ".INI") file(s) and values from 283 environment variables named: 284 .nf 285 \fBSNTP_<option-name>\fP or \fBSNTP\fP 286 .fi 287 .ad 288 The environmental presets take precedence (are processed later than) 289 the configuration files. 290 The \fIhomerc\fP files are "\fI$HOME\fP", and "\fI.\fP". 291 If any of these are directories, then the file \fI.ntprc\fP 292 is searched for within those directories. 293 .SH USAGE 294 .TP 7 295 .NOP \f[C]sntp ntpserver.somewhere\f[] 296 is the simplest use of this program 297 and can be run as an unprivileged command 298 to check the current time and error in the local clock. 299 .TP 7 300 .NOP \f[C]sntp \-Ss \-M 128 ntpserver.somewhere\f[] 301 With suitable privilege, 302 run as a command 303 or from a 304 \fCcron\f[]\fR(8)\f[] 305 job, 306 \f\*[B-Font]sntp \-Ss \-M 128 ntpserver.somewhere\f[] 307 will request the time from the server, 308 and if that server reports that it is synchronized 309 then if the offset adjustment is less than 128 milliseconds 310 the correction will be slewed, 311 and if the correction is more than 128 milliseconds 312 the correction will be stepped. 313 .TP 7 314 .NOP \f[C]sntp \-S ntpserver.somewhere\f[] 315 With suitable privilege, 316 run as a command 317 or from a 318 \fCcron\f[]\fR(8)\f[] 319 job, 320 \f\*[B-Font]sntp \-S ntpserver.somewhere\f[] 321 will set (step) the local clock from a synchronized specified server, 322 like the (deprecated) 323 \fCntpdate\f[]\fR(1ntpdatemdoc)\f[], 324 or 325 \fCrdate\f[]\fR(8)\f[] 326 commands. 327 .PP 328 .SH "ENVIRONMENT" 329 See \fBOPTION PRESETS\fP for configuration environment variables. 330 .SH "FILES" 331 See \fBOPTION PRESETS\fP for configuration files. 332 .SH "EXIT STATUS" 333 One of the following exit values will be returned: 334 .TP 335 .NOP 0 " (EXIT_SUCCESS)" 336 Successful program execution. 337 .TP 338 .NOP 1 " (EXIT_FAILURE)" 339 The operation failed or the command syntax was not valid. 340 .TP 341 .NOP 66 " (EX_NOINPUT)" 342 A specified configuration file could not be loaded. 343 .TP 344 .NOP 70 " (EX_SOFTWARE)" 345 libopts had an internal operational error. Please report 346 it to autogen-users (a] lists.sourceforge.net. Thank you. 347 .PP 348 .SH AUTHORS 349 .NOP "Johannes Maximilian Kuehn" 350 .br 351 .NOP "Harlan Stenn" 352 .br 353 .NOP "Dave Hart" 354 .br 355 .SH "COPYRIGHT" 356 Copyright (C) 1992-2024 The University of Delaware and Network Time Foundation all rights reserved. 357 This program is released under the terms of the NTP license, <http://ntp.org/license>. 358 .SH "BUGS" 359 Please send bug reports to: https://bugs.ntp.org, bugs (a] ntp.org 360 .SH "NOTES" 361 This manual page was \fIAutoGen\fP-erated from the \fBsntp\fP 362 option definitions. 363
Indexes created Fri Mar 27 00:22:57 UTC 2026