Sntp User's Manual

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Simple Network Time Protocol User Manual

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 4.2.6 of sntp.

The program implements the SNTP protocol as defined by the draft NTPv4 IETF specification.

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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.

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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