xref: /freebsd/contrib/ntp/sntp/sntp.texi (revision 416ba5c74546f32a993436a99516d35008e9f384)

\input texinfo    @c -*-texinfo-*-
@c %**start of header
@setfilename sntp.info
@settitle Sntp User's Manual
@include include/version.texi
@paragraphindent 2
@c %**end of header

@ifinfo
This file documents the use of the NTP Project's SNTP, a program for
querying and setting the time.
@end ifinfo

@direntry
* sntp: (sntp).                               Simple Network Time Protocol
@end direntry

@titlepage
@title Simple Network Time Protocol User's Manual
@subtitle sntp, version @value{VERSION}, @value{UPDATED}
@c @author Max @email{foo@ntp.org}
@end titlepage

@c @page
@c @vskip 0pt plus 1filll

@node Top, sntp Description, (dir), (dir)
@top Simple Network Time Protocol User Manual

This document describes the use of the NTP Project's @code{sntp} program,
that can be used to query a Network Time Protocol (NTP) server and
display the time offset of the system clock relative to the server
clock.  Run as root, it can correct the system clock to this offset as
well.  It can be run as an interactive command or from a cron job.

This document applies to version @value{VERSION} of @code{sntp}.

The program implements the SNTP protocol as defined by RFC 5905, the NTPv4
IETF specification.

@shortcontents

@menu
* sntp Description::            Description
* sntp Invocation::		Invoking sntp
* Usage::                       Usage
@end menu

@node sntp Description
@comment  node-name,  next,  previous,  up
@section Description

By default, @code{sntp} writes the local data and time (i.e., not UTC) to the
standard output in the format:

@example
1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 secs
@end example

where
YYYY-MM-DD HH:MM:SS.SUBSEC is the local date and time,
(+0800) is the local timezone adjustment (so we would add 8 hours and 0 minutes to convert the reported local time to UTC),
and
the +4.567 +/- 0.089 secs indicates the time offset and
error bound of the system clock relative to the server clock.

@include invoke-sntp.texi

@node Usage
@comment  node-name,  next,  previous,  up
@section Usage

The simplest use of this program is as an unprivileged command to
check the current time, offset, and error in the local clock.
For example:

@example
sntp ntpserver.somewhere
@end example

With suitable privilege, it can be run as a command or in a
@code{crom} job to reset the local clock from a reliable server, like
the @code{ntpdate} and @code{rdate} commands.
For example:

@example
sntp -a ntpserver.somewhere
@end example