Provided by: sntp_4.2.8p10+dfsg-5ubuntu7_amd64 bug

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 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 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 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 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 unlimited 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 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 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 constrained 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 communications.

     -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 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 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 loading 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 unprivileged 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 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.