sntp.8 revision 293896
1.Dd January 7 2016 2.Dt SNTP 8 User Commands 3.Os 4.\" EDIT THIS FILE WITH CAUTION (sntp-opts.mdoc) 5.\" 6.\" $FreeBSD: releng/9.3/usr.sbin/ntp/doc/sntp.8 293896 2016-01-14 09:11:26Z glebius $ 7.\" 8.\" It has been AutoGen-ed January 7, 2016 at 11:23:27 PM by AutoGen 5.18.5 9.\" From the definitions sntp-opts.def 10.\" and the template file agmdoc-cmd.tpl 11.Sh NAME 12.Nm sntp 13.Nd standard Simple Network Time Protocol client program 14.Sh SYNOPSIS 15.Nm 16.\" Mixture of short (flag) options and long options 17.Op Fl flags 18.Op Fl flag Op Ar value 19.Op Fl \-option\-name Ns Oo Oo Ns "=| " Oc Ns Ar value Oc 20[ hostname\-or\-IP ...] 21.Pp 22.Sh DESCRIPTION 23.Nm 24can be used as an SNTP client to query a NTP or SNTP server and either display 25the time or set the local system's time (given suitable privilege). It can be 26run as an interactive command or from a 27.Ic cron 28job. 29NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol) 30are defined and described by RFC 5905. 31.Pp 32The default is to write the estimated correct local date and time (i.e. not 33UTC) to the standard output in a format like: 34.Ic "'1996\-10\-15 20:17:25.123 (+0800) +4.567 +/\- 0.089 [host] IP sN'" 35where the 36.Ic "'(+0800)'" 37means that to get to UTC from the reported local time one must 38add 8 hours and 0 minutes, 39the 40.Ic "'+4.567'" 41indicates the local clock is 4.567 seconds behind the correct time 42(so 4.567 seconds must be added to the local clock to get it to be correct). 43Note that the number of decimals printed for this value will change 44based on the reported precision of the server. 45.Ic "'+/\- 0.089'" 46is the reported 47.Em synchronization distance 48(in seconds), which represents the maximum error due to all causes. 49If the server does not report valid data needed to calculate the 50synchronization distance, this will be reported as 51.Ic "'+/\- ?'" . 52If the 53.Em host 54is different from the 55.Em IP , 56both will be displayed. 57Otherwise, only the 58.Em IP 59is displayed. 60Finally, the 61.Em stratum 62of the host is reported 63and the leap indicator is decoded and displayed. 64.Sh "OPTIONS" 65.Bl -tag 66.It Fl 4 , Fl \-ipv4 67Force IPv4 DNS name resolution. 68This option must not appear in combination with any of the following options: 69ipv6. 70.sp 71Force DNS resolution of the following host names on the command line 72to the IPv4 namespace. 73.It Fl 6 , Fl \-ipv6 74Force IPv6 DNS name resolution. 75This option must not appear in combination with any of the following options: 76ipv4. 77.sp 78Force DNS resolution of the following host names on the command line 79to the IPv6 namespace. 80.It Fl a Ar auth\-keynumber , Fl \-authentication Ns = Ns Ar auth\-keynumber 81Enable authentication with the key \fBauth\-keynumber\fP. 82This option takes an integer number as its argument. 83.sp 84Enable authentication using the key specified in this option's 85argument. The argument of this option is the \fBkeyid\fP, a 86number specified in the \fBkeyfile\fP as this key's identifier. 87See the \fBkeyfile\fP option (\fB\-k\fP) for more details. 88.It Fl b Ar broadcast\-address , Fl \-broadcast Ns = Ns Ar broadcast\-address 89Listen to the address specified for broadcast time sync. 90This option may appear an unlimited number of times. 91.sp 92If specified \fBsntp\fP will listen to the specified address 93for NTP broadcasts. The default maximum wait time 94can (and probably should) be modified with \fB\-t\fP. 95.It Fl c Ar host\-name , Fl \-concurrent Ns = Ns Ar host\-name 96Concurrently query all IPs returned for host\-name. 97This option may appear an unlimited number of times. 98.sp 99Requests from an NTP "client" to a "server" should never be sent 100more rapidly than one every 2 seconds. By default, any IPs returned 101as part of a DNS lookup are assumed to be for a single instance of 102\fBntpd\fP, and therefore \fBsntp\fP will send queries to these IPs 103one after another, with a 2\-second gap in between each query. 104.sp 105The \fB\-c\fP or \fB\-\-concurrent\fP flag says that any IPs 106returned for the DNS lookup of the supplied host\-name are on 107different machines, so we can send concurrent queries. 108.It Fl d , Fl \-debug\-level 109Increase debug verbosity level. 110This option may appear an unlimited number of times. 111.sp 112.It Fl D Ar number , Fl \-set\-debug\-level Ns = Ns Ar number 113Set the debug verbosity level. 114This option may appear an unlimited number of times. 115This option takes an integer number as its argument. 116.sp 117.It Fl g Ar milliseconds , Fl \-gap Ns = Ns Ar milliseconds 118The gap (in milliseconds) between time requests. 119This option takes an integer number as its argument. 120The default 121.Ar milliseconds 122for this option is: 123.ti +4 124 50 125.sp 126Since we're only going to use the first valid response we get and 127there is benefit to specifying a good number of servers to query, 128separate the queries we send out by the specified number of 129milliseconds. 130.It Fl K Ar file\-name , Fl \-kod Ns = Ns Ar file\-name 131KoD history filename. 132The default 133.Ar file\-name 134for this option is: 135.ti +4 136 /var/db/ntp\-kod 137.sp 138Specifies the filename to be used for the persistent history of KoD 139responses received from servers. If the file does not exist, a 140warning message will be displayed. The file will not be created. 141.It Fl k Ar file\-name , Fl \-keyfile Ns = Ns Ar file\-name 142Look in this file for the key specified with \fB\-a\fP. 143.sp 144This option specifies the keyfile. 145\fBsntp\fP will search for the key specified with \fB\-a\fP 146\fIkeyno\fP in this file. See \fBntp.keys(5)\fP for more 147information. 148.It Fl l Ar file\-name , Fl \-logfile Ns = Ns Ar file\-name 149Log to specified logfile. 150.sp 151This option causes the client to write log messages to the specified 152\fIlogfile\fP. 153.It Fl M Ar number , Fl \-steplimit Ns = Ns Ar number 154Adjustments less than \fBsteplimit\fP msec will be slewed. 155This option takes an integer number as its argument. 156The value of 157.Ar number 158is constrained to being: 159.in +4 160.nf 161.na 162greater than or equal to 0 163.fi 164.in -4 165.sp 166If the time adjustment is less than \fIsteplimit\fP milliseconds, 167slew the amount using \fBadjtime(2)\fP. Otherwise, step the 168correction using \fBsettimeofday(2)\fP. The default value is 0, 169which means all adjustments will be stepped. This is a feature, as 170different situations demand different values. 171.It Fl o Ar number , Fl \-ntpversion Ns = Ns Ar number 172Send \fBint\fP as our NTP protocol version. 173This option takes an integer number as its argument. 174The value of 175.Ar number 176is constrained to being: 177.in +4 178.nf 179.na 180in the range 0 through 7 181.fi 182.in -4 183The default 184.Ar number 185for this option is: 186.ti +4 187 4 188.sp 189When sending requests to a remote server, tell them we are running 190NTP protocol version \fIntpversion\fP . 191.It Fl r , Fl \-usereservedport 192Use the NTP Reserved Port (port 123). 193.sp 194Use port 123, which is reserved for NTP, for our network 195communications. 196.It Fl S , Fl \-step 197OK to 'step' the time with \fBsettimeofday(2)\fP. 198.sp 199.It Fl s , Fl \-slew 200OK to 'slew' the time with \fBadjtime(2)\fP. 201.sp 202.It Fl t Ar seconds , Fl \-timeout Ns = Ns Ar seconds 203The number of seconds to wait for responses. 204This option takes an integer number as its argument. 205The default 206.Ar seconds 207for this option is: 208.ti +4 209 5 210.sp 211When waiting for a reply, \fBsntp\fP will wait the number 212of seconds specified before giving up. The default should be 213more than enough for a unicast response. If \fBsntp\fP is 214only waiting for a broadcast response a longer timeout is 215likely needed. 216.It Fl \-wait , " Fl \-no\-wait" 217Wait for pending replies (if not setting the time). 218The \fIno\-wait\fP form will disable the option. 219This option is enabled by default. 220.sp 221If we are not setting the time, wait for all pending responses. 222.It Fl \&? , Fl \-help 223Display usage information and exit. 224.It Fl \&! , Fl \-more\-help 225Pass the extended usage information through a pager. 226.It Fl > Oo Ar cfgfile Oc , Fl \-save\-opts Oo Ns = Ns Ar cfgfile Oc 227Save the option state to \fIcfgfile\fP. The default is the \fIlast\fP 228configuration file listed in the \fBOPTION PRESETS\fP section, below. 229The command will exit after updating the config file. 230.It Fl < Ar cfgfile , Fl \-load\-opts Ns = Ns Ar cfgfile , Fl \-no\-load\-opts 231Load options from \fIcfgfile\fP. 232The \fIno\-load\-opts\fP form will disable the loading 233of earlier config/rc/ini files. \fI\-\-no\-load\-opts\fP is handled early, 234out of order. 235.It Fl \-version Op Brq Ar v|c|n 236Output version of program and exit. The default mode is `v', a simple 237version. The `c' mode will print copyright information and `n' will 238print the full copyright notice. 239.El 240.Sh "OPTION PRESETS" 241Any option that is not marked as \fInot presettable\fP may be preset 242by loading values from configuration ("RC" or ".INI") file(s) and values from 243environment variables named: 244.nf 245 \fBSNTP_<option\-name>\fP or \fBSNTP\fP 246.fi 247.ad 248The environmental presets take precedence (are processed later than) 249the configuration files. 250The \fIhomerc\fP files are "\fI$HOME\fP", and "\fI.\fP". 251If any of these are directories, then the file \fI.ntprc\fP 252is searched for within those directories. 253.Sh USAGE 254.Bl -tag -width indent 255.It Li "sntp ntpserver.somewhere" 256is the simplest use of this program 257and can be run as an unprivileged command 258to check the current time and error in the local clock. 259.It Li "sntp \-Ss \-M 128 ntpserver.somewhere" 260With suitable privilege, 261run as a command 262or from a 263.Xr cron 8 264job, 265.Ic "sntp \-Ss \-M 128 ntpserver.somewhere" 266will request the time from the server, 267and if that server reports that it is synchronized 268then if the offset adjustment is less than 128 milliseconds 269the correction will be slewed, 270and if the correction is more than 128 milliseconds 271the correction will be stepped. 272.It Li "sntp \-S ntpserver.somewhere" 273With suitable privilege, 274run as a command 275or from a 276.Xr cron 8 277job, 278.Ic "sntp \-S ntpserver.somewhere" 279will set (step) the local clock from a synchronized specified server, 280like the (deprecated) 281.Xr ntpdate 8 , 282or 283.Xr rdate 8 284commands. 285.El 286.Sh "ENVIRONMENT" 287See \fBOPTION PRESETS\fP for configuration environment variables. 288.Sh "FILES" 289See \fBOPTION PRESETS\fP for configuration files. 290.Sh "EXIT STATUS" 291One of the following exit values will be returned: 292.Bl -tag 293.It 0 " (EXIT_SUCCESS)" 294Successful program execution. 295.It 1 " (EXIT_FAILURE)" 296The operation failed or the command syntax was not valid. 297.It 66 " (EX_NOINPUT)" 298A specified configuration file could not be loaded. 299.It 70 " (EX_SOFTWARE)" 300libopts had an internal operational error. Please report 301it to autogen\-users@lists.sourceforge.net. Thank you. 302.El 303.Sh AUTHORS 304.An "Johannes Maximilian Kuehn" 305.An "Harlan Stenn" 306.An "Dave Hart" 307.Sh "COPYRIGHT" 308Copyright (C) 1992\-2015 The University of Delaware and Network Time Foundation all rights reserved. 309This program is released under the terms of the NTP license, <http://ntp.org/license>. 310.Sh "BUGS" 311Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org 312.Sh "NOTES" 313This manual page was \fIAutoGen\fP\-erated from the \fBsntp\fP 314option definitions. 315