1.\" $OpenBSD: rdate.8,v 1.30 2007/05/31 19:20:28 jmc 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: May 31 2007 $ 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 46acnpsv 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 868 TCP protocol server, 47which is usually implemented as a built-in service of 48.Xr inetd 8 , 49or an RFC 2030 protocol SNTP/NTP server. 50By default, 51.Nm 52uses the RFC 868 TCP 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. 71Sometimes required when synchronizing to an NTP server. 72When synchronizing using the RFC 868 protocol, use this option only if the 73server does not correctly account for leap seconds. 74You can determine if you need this parameter if you sync against an NTP 75server (with this parameter) or (recommended) check with a local radio 76controlled watch or phone service. 77.It Fl n 78Use SNTP (RFC 2030) instead of the RFC 868 time protocol. 79.It Fl p 80Do not set, just print the remote time. 81.It Fl s 82Do not print the time. 83.It Fl v 84Verbose output. 85Always show the adjustment. 86.El 87.Sh FILES 88.Bl -tag -width /var/log/wtmp -compact 89.It Pa /var/log/wtmp 90record of date resets and time changes 91.El 92.Sh EXAMPLES 93To get the legal time in Germany, set the 94.Pa /etc/localtime 95symlink to 96.Pa /usr/share/zoneinfo/right/Europe/Berlin 97and issue the following command: 98.Pp 99.D1 Li "# rdate -ncv ptbtime1.ptb.de" 100.Pp 101The command of course assumes you have a working internet connection 102and DNS set up to connect to the server at 103.Sy Physikalisch-Technische Bundesanstalt 104in Braunschweig, Germany. 105.Pp 106To gradually adjust time once an hour after the first 107.Qq step 108adjustment, put the following line into root's crontab: 109.Pp 110.D1 Li "58 * * * * rdate -ncav ptbtime1.ptb.de | logger -t NTP" 111.Sh SEE ALSO 112.Xr date 1 , 113.Xr adjtime 2 , 114.Xr inetd 8 , 115.Xr ntpd 8 , 116.Xr timed 8 117