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This file documents the use of the NTP Project's ntpdc, a program for controlling ntpd.

ntpdc: NTPD Control User Manual
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This document describes the use of the NTP Project's ntpdc 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 VERSION of ntpdc.

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

Description
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By default, ntpdc writes the local data and time (i.e., not UTC) to the standard output in the format:

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

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.

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Usage
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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:

     ntpdc ntpserver.somewhere

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

     ntpdc -a ntpserver.somewhere