320 lines
11 KiB
Groff
320 lines
11 KiB
Groff
.Dd August 14 2018
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.Dt SNTP 8 User Commands
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.Os
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.\" EDIT THIS FILE WITH CAUTION (sntp-opts.mdoc)
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.\"
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.\" $FreeBSD$
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.\"
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.\" It has been AutoGen-ed August 14, 2018 at 08:27:40 AM by AutoGen 5.18.5
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.\" From the definitions sntp-opts.def
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.\" and the template file agmdoc-cmd.tpl
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.Sh NAME
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.Nm sntp
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.Nd standard Simple Network Time Protocol client program
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.Sh SYNOPSIS
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.Nm
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.\" Mixture of short (flag) options and long options
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.Op Fl flags
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.Op Fl flag Op Ar value
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.Op Fl \-option\-name Ns Oo Oo Ns "=| " Oc Ns Ar value Oc
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[ hostname\-or\-IP ...]
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.Pp
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.Sh DESCRIPTION
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.Nm
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can be used as an SNTP client to query a NTP or SNTP server and either display
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the time or set the local system's time (given suitable privilege). It can be
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run as an interactive command or from a
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.Ic cron
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job.
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NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol)
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are defined and described by RFC 5905.
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.Pp
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The default is to write the estimated correct local date and time (i.e. not
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UTC) to the standard output in a format like:
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.Ic "'1996\-10\-15 20:17:25.123 (+0800) +4.567 +/\- 0.089 [host] IP sN'"
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where the
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.Ic "'(+0800)'"
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means that to get to UTC from the reported local time one must
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add 8 hours and 0 minutes,
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the
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.Ic "'+4.567'"
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indicates the local clock is 4.567 seconds behind the correct time
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(so 4.567 seconds must be added to the local clock to get it to be correct).
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Note that the number of decimals printed for this value will change
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based on the reported precision of the server.
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.Ic "'+/\- 0.089'"
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is the reported
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.Em synchronization distance
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(in seconds), which represents the maximum error due to all causes.
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If the server does not report valid data needed to calculate the
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synchronization distance, this will be reported as
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.Ic "'+/\- ?'" .
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If the
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.Em host
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is different from the
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.Em IP ,
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both will be displayed.
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Otherwise, only the
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.Em IP
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is displayed.
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Finally, the
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.Em stratum
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of the host is reported
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and the leap indicator is decoded and displayed.
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.Sh "OPTIONS"
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.Bl -tag
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.It Fl 4 , Fl \-ipv4
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Force IPv4 DNS name resolution.
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This option must not appear in combination with any of the following options:
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ipv6.
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.sp
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Force DNS resolution of the following host names on the command line
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to the IPv4 namespace.
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.It Fl 6 , Fl \-ipv6
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Force IPv6 DNS name resolution.
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This option must not appear in combination with any of the following options:
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ipv4.
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.sp
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Force DNS resolution of the following host names on the command line
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to the IPv6 namespace.
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.It Fl a Ar auth\-keynumber , Fl \-authentication Ns = Ns Ar auth\-keynumber
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Enable authentication with the key \fBauth\-keynumber\fP.
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This option takes an integer number as its argument.
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.sp
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Enable authentication using the key specified in this option's
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argument. The argument of this option is the \fBkeyid\fP, a
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number specified in the \fBkeyfile\fP as this key's identifier.
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See the \fBkeyfile\fP option (\fB\-k\fP) for more details.
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.It Fl b Ar broadcast\-address , Fl \-broadcast Ns = Ns Ar broadcast\-address
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Listen to the address specified for broadcast time sync.
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This option may appear an unlimited number of times.
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.sp
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If specified \fBsntp\fP will listen to the specified address
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for NTP broadcasts. The default maximum wait time
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can (and probably should) be modified with \fB\-t\fP.
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.It Fl c Ar host\-name , Fl \-concurrent Ns = Ns Ar host\-name
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Concurrently query all IPs returned for host\-name.
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This option may appear an unlimited number of times.
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.sp
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Requests from an NTP "client" to a "server" should never be sent
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more rapidly than one every 2 seconds. By default, any IPs returned
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as part of a DNS lookup are assumed to be for a single instance of
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\fBntpd\fP, and therefore \fBsntp\fP will send queries to these IPs
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one after another, with a 2\-second gap in between each query.
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.sp
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The \fB\-c\fP or \fB\-\-concurrent\fP flag says that any IPs
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returned for the DNS lookup of the supplied host\-name are on
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different machines, so we can send concurrent queries.
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.It Fl d , Fl \-debug\-level
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Increase debug verbosity level.
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This option may appear an unlimited number of times.
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.sp
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.It Fl D Ar number , Fl \-set\-debug\-level Ns = Ns Ar number
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Set the debug verbosity level.
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This option may appear an unlimited number of times.
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This option takes an integer number as its argument.
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.sp
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.It Fl g Ar milliseconds , Fl \-gap Ns = Ns Ar milliseconds
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The gap (in milliseconds) between time requests.
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This option takes an integer number as its argument.
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The default
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.Ar milliseconds
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for this option is:
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.ti +4
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50
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.sp
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Since we're only going to use the first valid response we get and
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there is benefit to specifying a good number of servers to query,
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separate the queries we send out by the specified number of
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milliseconds.
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.It Fl K Ar file\-name , Fl \-kod Ns = Ns Ar file\-name
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KoD history filename.
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The default
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.Ar file\-name
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for this option is:
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.ti +4
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/var/db/ntp\-kod
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.sp
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Specifies the filename to be used for the persistent history of KoD
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responses received from servers. If the file does not exist, a
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warning message will be displayed. The file will not be created.
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.It Fl k Ar file\-name , Fl \-keyfile Ns = Ns Ar file\-name
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Look in this file for the key specified with \fB\-a\fP.
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The default
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.Ar file\-name
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for this option is:
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.ti +4
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/etc/ntp.keys
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.sp
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This option specifies the keyfile.
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\fBsntp\fP will search for the key specified with \fB\-a\fP
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\fIkeyno\fP in this file. See \fBntp.keys(5)\fP for more
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information.
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.It Fl l Ar file\-name , Fl \-logfile Ns = Ns Ar file\-name
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Log to specified logfile.
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.sp
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This option causes the client to write log messages to the specified
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\fIlogfile\fP.
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.It Fl M Ar number , Fl \-steplimit Ns = Ns Ar number
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Adjustments less than \fBsteplimit\fP msec will be slewed.
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This option takes an integer number as its argument.
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The value of
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.Ar number
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is constrained to being:
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.in +4
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.nf
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.na
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greater than or equal to 0
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.fi
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.in -4
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.sp
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If the time adjustment is less than \fIsteplimit\fP milliseconds,
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slew the amount using \fBadjtime(2)\fP. Otherwise, step the
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correction using \fBsettimeofday(2)\fP. The default value is 0,
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which means all adjustments will be stepped. This is a feature, as
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different situations demand different values.
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.It Fl o Ar number , Fl \-ntpversion Ns = Ns Ar number
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Send \fBint\fP as our NTP protocol version.
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This option takes an integer number as its argument.
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The value of
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.Ar number
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is constrained to being:
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.in +4
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.nf
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.na
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in the range 0 through 7
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.fi
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.in -4
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The default
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.Ar number
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for this option is:
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.ti +4
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4
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.sp
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When sending requests to a remote server, tell them we are running
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NTP protocol version \fIntpversion\fP .
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.It Fl r , Fl \-usereservedport
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Use the NTP Reserved Port (port 123).
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.sp
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Use port 123, which is reserved for NTP, for our network
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communications.
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.It Fl S , Fl \-step
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OK to 'step' the time with \fBsettimeofday(2)\fP.
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.sp
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.It Fl s , Fl \-slew
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OK to 'slew' the time with \fBadjtime(2)\fP.
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.sp
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.It Fl t Ar seconds , Fl \-timeout Ns = Ns Ar seconds
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The number of seconds to wait for responses.
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This option takes an integer number as its argument.
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The default
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.Ar seconds
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for this option is:
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.ti +4
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5
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.sp
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When waiting for a reply, \fBsntp\fP will wait the number
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of seconds specified before giving up. The default should be
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more than enough for a unicast response. If \fBsntp\fP is
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only waiting for a broadcast response a longer timeout is
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likely needed.
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.It Fl \-wait , Fl \-no\-wait
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Wait for pending replies (if not setting the time).
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The \fIno\-wait\fP form will disable the option.
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This option is enabled by default.
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.sp
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If we are not setting the time, wait for all pending responses.
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.It Fl \&? , Fl \-help
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Display usage information and exit.
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.It Fl \&! , Fl \-more\-help
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Pass the extended usage information through a pager.
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.It Fl > Oo Ar cfgfile Oc , Fl \-save\-opts Oo Ns = Ns Ar cfgfile Oc
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Save the option state to \fIcfgfile\fP. The default is the \fIlast\fP
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configuration file listed in the \fBOPTION PRESETS\fP section, below.
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The command will exit after updating the config file.
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.It Fl < Ar cfgfile , Fl \-load\-opts Ns = Ns Ar cfgfile , Fl \-no\-load\-opts
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Load options from \fIcfgfile\fP.
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The \fIno\-load\-opts\fP form will disable the loading
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of earlier config/rc/ini files. \fI\-\-no\-load\-opts\fP is handled early,
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out of order.
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.It Fl \-version Op Brq Ar v|c|n
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Output version of program and exit. The default mode is `v', a simple
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version. The `c' mode will print copyright information and `n' will
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print the full copyright notice.
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.El
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.Sh "OPTION PRESETS"
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Any option that is not marked as \fInot presettable\fP may be preset
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by loading values from configuration ("RC" or ".INI") file(s) and values from
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environment variables named:
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.nf
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\fBSNTP_<option\-name>\fP or \fBSNTP\fP
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.fi
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.ad
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The environmental presets take precedence (are processed later than)
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the configuration files.
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The \fIhomerc\fP files are "\fI$HOME\fP", and "\fI.\fP".
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If any of these are directories, then the file \fI.ntprc\fP
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is searched for within those directories.
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.Sh USAGE
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.Bl -tag -width indent
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.It Li "sntp ntpserver.somewhere"
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is the simplest use of this program
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and can be run as an unprivileged command
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to check the current time and error in the local clock.
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.It Li "sntp \-Ss \-M 128 ntpserver.somewhere"
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With suitable privilege,
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run as a command
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or from a
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.Xr cron 8
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job,
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.Ic "sntp \-Ss \-M 128 ntpserver.somewhere"
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will request the time from the server,
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and if that server reports that it is synchronized
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then if the offset adjustment is less than 128 milliseconds
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the correction will be slewed,
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and if the correction is more than 128 milliseconds
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the correction will be stepped.
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.It Li "sntp \-S ntpserver.somewhere"
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With suitable privilege,
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run as a command
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or from a
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.Xr cron 8
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job,
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.Ic "sntp \-S ntpserver.somewhere"
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will set (step) the local clock from a synchronized specified server,
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like the (deprecated)
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.Xr ntpdate 8 ,
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or
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.Xr rdate 8
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commands.
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.El
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.Sh "ENVIRONMENT"
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See \fBOPTION PRESETS\fP for configuration environment variables.
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.Sh "FILES"
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See \fBOPTION PRESETS\fP for configuration files.
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.Sh "EXIT STATUS"
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One of the following exit values will be returned:
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.Bl -tag
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.It 0 " (EXIT_SUCCESS)"
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Successful program execution.
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.It 1 " (EXIT_FAILURE)"
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The operation failed or the command syntax was not valid.
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.It 66 " (EX_NOINPUT)"
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A specified configuration file could not be loaded.
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.It 70 " (EX_SOFTWARE)"
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libopts had an internal operational error. Please report
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it to autogen\-users@lists.sourceforge.net. Thank you.
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.El
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.Sh AUTHORS
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.An "Johannes Maximilian Kuehn"
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.An "Harlan Stenn"
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.An "Dave Hart"
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.Sh "COPYRIGHT"
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Copyright (C) 1992\-2017 The University of Delaware and Network Time Foundation all rights reserved.
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This program is released under the terms of the NTP license, <http://ntp.org/license>.
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.Sh "BUGS"
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Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org
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.Sh "NOTES"
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This manual page was \fIAutoGen\fP\-erated from the \fBsntp\fP
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option definitions.
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