1.\" $OpenBSD: rdate.8,v 1.37 2015/02/10 13:10:27 deraadt Exp $ 2.\" $NetBSD: rdate.8,v 1.4 1996/04/08 20:55:17 jtc Exp $ 3.\" 4.\" Copyright (c) 1994 Christos Zoulas 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by Christos Zoulas. 18.\" 4. The name of the author may not be used to endorse or promote products 19.\" derived from this software without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 22.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 23.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 24.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 25.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 26.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 30.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31.\" 32.Dd $Mdocdate: February 10 2015 $ 33.Dt RDATE 8 34.Os 35.Sh NAME 36.Nm rdate 37.Nd set the system's date from a remote host 38.Sh SYNOPSIS 39.Nm rdate 40.Op Fl 46acnopsv 41.Ar host 42.Sh DESCRIPTION 43.Nm 44displays and sets the local date and time from the 45host name or address given as the argument. 46The time source may be an RFC 5905 protocol SNTP/NTP server 47or an RFC 868 TCP protocol server, 48which is usually implemented as a built-in service of 49.Xr inetd 8 . 50By default, 51.Nm 52uses the RFC 5905 SNTP/NTP protocol. 53.Pp 54The options are as follows: 55.Bl -tag -width Ds 56.It Fl 4 57Forces 58.Nm 59to use IPv4 addresses only. 60.It Fl 6 61Forces 62.Nm 63to use IPv6 addresses only. 64.It Fl a 65Use the 66.Xr adjtime 2 67call to gradually skew the local time to the 68remote time rather than just hopping. 69.It Fl c 70Correct leap seconds. 71This should be used only when synchronizing to a server 72which does not correctly account for leap seconds. 73.It Fl n 74Use SNTP (RFC 5905) instead of the RFC 868 time protocol. 75This is the default. 76This protocol counts 32 bits of seconds from January 1, 1900 77and will rollover in March 2036. 78.It Fl o 79Use an RFC 868 TCP protocol server instead of SNTP. 80This protocol is obsolete as it is not capable of representing 81dates past January 19, 2038 03:14:07 GMT. 82.It Fl p 83Do not set, just print the remote time. 84.It Fl s 85Do not print the time. 86.It Fl v 87Verbose output. 88Always show the adjustment. 89.El 90.Sh FILES 91.Bl -tag -width /var/log/wtmp -compact 92.It Pa /var/log/wtmp 93record of date resets and time changes 94.El 95.Sh EXAMPLES 96To get the legal time in Germany, set the 97.Pa /etc/localtime 98symlink to 99.Pa /usr/share/zoneinfo/right/Europe/Berlin 100and issue the following command: 101.Pp 102.D1 Li "# rdate -v ptbtime1.ptb.de" 103.Pp 104The command of course assumes you have a working internet connection 105and DNS set up to connect to the server at 106.Sy Physikalisch-Technische Bundesanstalt 107in Braunschweig, Germany. 108.Sh SEE ALSO 109.Xr date 1 , 110.Xr adjtime 2 , 111.Xr inetd 8 , 112.Xr ntpd 8 113