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SNTP(8)			FreeBSD	System Manager's Manual		       SNTP(8)

NAME
     sntp -- standard Simple Network Time Protocol client program

SYNOPSIS
     sntp [-flags] [-flag [value]] [--option-name[[=| ]value]] [ host-
	  name-or-IP ...]

DESCRIPTION
     sntp can be used as an SNTP client	to query a NTP or SNTP server and
     either display the	time or	set the	local system's time (given suitable
     privilege).  It can be run	as an interactive command or from a cron job.
     NTP (the Network Time Protocol) and SNTP (the Simple Network Time Proto-
     col) are defined and described by RFC 5905.

     The default is to write the estimated correct local date and time (i.e.
     not UTC) to the standard output in	a format like: '1996-10-15
     20:17:25.123 (+0800) +4.567 +/- 0.089 [host] IP sN' where the '(+0800)'
     means that	to get to UTC from the reported	local time one must add	8
     hours and 0 minutes, the '+4.567' indicates the local clock is 4.567 sec-
     onds behind the correct time (so 4.567 seconds must be added to the local
     clock to get it to	be correct).  Note that	the number of decimals printed
     for this value will change	based on the reported precision	of the server.
     '+/- 0.089' is the	reported synchronization distance (in seconds),	which
     represents	the maximum error due to all causes.  If the server does not
     report valid data needed to calculate the synchronization distance, this
     will be reported as '+/- ?'.  If the host is different from the IP, both
     will be displayed.	 Otherwise, only the IP	is displayed.  Finally,	the
     stratum of	the host is reported and the leap indicator is decoded and
     displayed.

OPTIONS
     -4, --ipv4	 Force IPv4 DNS	name resolution.  This option must not appear
		 in combination	with any of the	following options: ipv6.

		 Force DNS resolution of the following host names on the com-
		 mand line to the IPv4 namespace.

     -6, --ipv6	 Force IPv6 DNS	name resolution.  This option must not appear
		 in combination	with any of the	following options: ipv4.

		 Force DNS resolution of the following host names on the com-
		 mand line to the IPv6 namespace.

     -a	auth-keynumber,	--authentication=auth-keynumber
		 Enable	authentication with the	key auth-keynumber.  This
		 option	takes an integer number	as its argument.

		 Enable	authentication using the key specified in this
		 option's argument.  The argument of this option is the	keyid,
		 a number specified in the keyfile as this key's identifier.
		 See the keyfile option	(-k) for more details.

     -b	broadcast-address, --broadcast=broadcast-address
		 Listen	to the address specified for broadcast time sync.
		 This option may appear	an unlimited number of times.

		 If specified sntp will	listen to the specified	address	for
		 NTP broadcasts.  The default maximum wait time	can (and prob-
		 ably should) be modified with -t.

     -c	host-name, --concurrent=host-name
		 Concurrently query all	IPs returned for host-name.  This
		 option	may appear an unlimited	number of times.

		 Requests from an NTP "client" to a "server" should never be
		 sent more rapidly than	one every 2 seconds.  By default, any
		 IPs returned as part of a DNS lookup are assumed to be	for a
		 single	instance of ntpd, and therefore	sntp will send queries
		 to these IPs one after	another, with a	2-second gap in
		 between each query.

		 The -c	or --concurrent	flag says that any IPs returned	for
		 the DNS lookup	of the supplied	host-name are on different
		 machines, so we can send concurrent queries.

     -d, --debug-level
		 Increase debug	verbosity level.  This option may appear an
		 unlimited number of times.

     -D	number,	--set-debug-level=number
		 Set the debug verbosity level.	 This option may appear	an
		 unlimited number of times.  This option takes an integer num-
		 ber as	its argument.

     -g	milliseconds, --gap=milliseconds
		 The gap (in milliseconds) between time	requests.  This	option
		 takes an integer number as its	argument.  The default
		 milliseconds for this option is:
		      50

		 Since we're only going	to use the first valid response	we get
		 and there is benefit to specifying a good number of servers
		 to query, separate the	queries	we send	out by the specified
		 number	of milliseconds.

     -K	file-name, --kod=file-name
		 KoD history filename.	The default file-name for this option
		 is:
		      /var/db/ntp-kod

		 Specifies the filename	to be used for the persistent history
		 of KoD	responses received from	servers.  If the file does not
		 exist,	a warning message will be displayed.  The file will
		 not be	created.

     -k	file-name, --keyfile=file-name
		 Look in this file for the key specified with -a.

		 This option specifies the keyfile.  sntp will search for the
		 key specified with -a keyno in	this file.  See	ntp.keys(5)
		 for more information.

     -l	file-name, --logfile=file-name
		 Log to	specified logfile.

		 This option causes the	client to write	log messages to	the
		 specified logfile.

     -M	number,	--steplimit=number
		 Adjustments less than steplimit msec will be slewed.  This
		 option	takes an integer number	as its argument.  The value of
		 number	is constrained to being:
		     greater than or equal to 0

		 If the	time adjustment	is less	than steplimit milliseconds,
		 slew the amount using adjtime(2).  Otherwise, step the	cor-
		 rection using settimeofday(2).	 The default value is 0, which
		 means all adjustments will be stepped.	 This is a feature, as
		 different situations demand different values.

     -o	number,	--ntpversion=number
		 Send int as our NTP protocol version.	This option takes an
		 integer number	as its argument.  The value of number is con-
		 strained to being:
		     in	the range  0 through 7
		 The default number for	this option is:
		      4

		 When sending requests to a remote server, tell	them we	are
		 running NTP protocol version ntpversion .

     -r, --usereservedport
		 Use the NTP Reserved Port (port 123).

		 Use port 123, which is	reserved for NTP, for our network com-
		 munications.

     -S, --step	 OK to 'step' the time with settimeofday(2).

     -s, --slew	 OK to 'slew' the time with adjtime(2).

     -t	seconds, --timeout=seconds
		 The number of seconds to wait for responses.  This option
		 takes an integer number as its	argument.  The default seconds
		 for this option is:
		      5

		 When waiting for a reply, sntp	will wait the number of	sec-
		 onds specified	before giving up.  The default should be more
		 than enough for a unicast response.  If sntp is only waiting
		 for a broadcast response a longer timeout is likely needed.

     --wait, --no-wait
		 Wait for pending replies (if not setting the time).  The
		 no-wait form will disable the option.	This option is enabled
		 by default.

		 If we are not setting the time, wait for all pending
		 responses.

     -?, --help	 Display usage information and exit.

     -!, --more-help
		 Pass the extended usage information through a pager.

     ->	[cfgfile], --save-opts [=cfgfile]
		 Save the option state to cfgfile.  The	default	is the last
		 configuration file listed in the OPTION PRESETS section,
		 below.	 The command will exit after updating the config file.

     -<	cfgfile, --load-opts=cfgfile, --no-load-opts
		 Load options from cfgfile.  The no-load-opts form will	dis-
		 able the loading of earlier config/rc/ini files.
		 --no-load-opts	is handled early, out of order.

     --version [{v|c|n}]
		 Output	version	of program and exit.  The default mode is `v',
		 a simple version.  The	`c' mode will print copyright informa-
		 tion and `n' will print the full copyright notice.

OPTION PRESETS
     Any option	that is	not marked as not presettable may be preset by loading
     values from configuration ("RC" or	".INI")	file(s)	and values from	envi-
     ronment variables named:
       SNTP_<option-name> or SNTP
     The  environmental	presets	take precedence	(are processed later than) the
     configuration files.  The homerc files are	"$HOME", and ".".  If  any  of
     these  are	directories, then the file .ntprc is searched for within those
     directories.

USAGE
     sntp ntpserver.somewhere
	     is	the simplest use of this program and can be run	as an unprivi-
	     leged command to check the	current	time and error in the local
	     clock.

     sntp -Ss -M 128 ntpserver.somewhere
	     With suitable privilege, run as a command or from a cron(8) job,
	     sntp -Ss -M 128 ntpserver.somewhere will request the time from
	     the server, and if	that server reports that it is synchronized
	     then if the offset	adjustment is less than	128 milliseconds the
	     correction	will be	slewed,	and if the correction is more than 128
	     milliseconds the correction  will be stepped.

     sntp -S ntpserver.somewhere
	     With suitable privilege, run as a command or from a cron(8) job,
	     sntp -S ntpserver.somewhere will set (step) the local clock from
	     a synchronized specified server, like the (deprecated)
	     ntpdate(8), or rdate(8) commands.

ENVIRONMENT
     See OPTION	PRESETS	for configuration environment variables.

FILES
     See OPTION	PRESETS	for configuration files.

EXIT STATUS
     One of the	following exit values will be returned:

     0	(EXIT_SUCCESS)
		   Successful program execution.

     1	(EXIT_FAILURE)
		   The operation failed	or the command syntax was not valid.

     66	 (EX_NOINPUT)
		   A specified configuration file could	not be loaded.

     70	 (EX_SOFTWARE)
		   libopts had an internal operational error.  Please report
		   it to autogen-users@lists.sourceforge.net.  Thank you.

AUTHORS
     Johannes Maximilian Kuehn
     Harlan Stenn
     Dave Hart

COPYRIGHT
     Copyright (C) 1992-2017 The University of Delaware	and Network Time Foun-
     dation all	rights reserved.  This program is released under the terms of
     the NTP license, <http://ntp.org/license>.

BUGS
     Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org

NOTES
     This manual page was AutoGen-erated from the sntp option definitions.

FreeBSD	11.1			 March 21 2017			  FreeBSD 11.1

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPTION PRESETS | USAGE | ENVIRONMENT | FILES | EXIT STATUS | AUTHORS | COPYRIGHT | BUGS | NOTES

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