This document describes the use of the NTP Project's 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 4.2.7p50 of sntp.
The program implements the SNTP protocol as defined by the draft NTPv4 IETF specification.
By default, sntp writes the local data and time (i.e., not UTC) to the
standard output in the format:
1996 Oct 15 20:17:25.123 +4.567 +/- 0.089 secs
where the +4.567 +/- 0.089 secs indicates the time offset and error bound of the system clock relative to the server clock.
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:
sntp ntpserver.somewhere
With suitable privilege, it can be run as a command or in a
crom job to reset the local clock from a reliable server, like
the ntpdate and rdate commands.
For example:
sntp -a ntpserver.somewhere