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sntp(8)				 User Commands			       sntp(8)



NAME
       sntp - standard Simple Network Time Protocol client program

SYNOPSIS
       sntp  [-flags]  [-flag [value]] [--option-name[[=| ]value]] [ hostname-
       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
       Protocol) 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
       seconds	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  synchroniza-
       tion  distance,	this will be reported as '+/- ?'.  If the host is dif-
       ferent 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 command
	      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 command
	      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 key-
	      file 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  probably
	      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 unlim-
	      ited  number  of	times.	This option takes an integer number 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 millisec-
	      onds 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/lib/ntp/sntp-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.	  The  default
	      file-name for this option is:
		   /etc/ntp.keys

	      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 spec-
	      ified 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 correction
	      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 run-
	      ning NTP protocol version ntpversion .

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

	      Use port 123, which is reserved for NTP, for our network commu-
	      nications.

       -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 seconds
	      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, - Fl -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 con-
	      figuration 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 disable
	      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 information
	      and `n' will print the full copyright notice.

OPTION PRESETS
       Any option that is not marked as not presettable may be preset by load-
       ing values from configuration ("RC" or ".INI") file(s) and values from
       environment 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 unpriv-
	      ileged  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) ntp-
	      date(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
       Foundation 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.



4.2.8p12			  14 Aug 2018			       sntp(8)