rdate - set the system’s date from a remote host
rdate [-46acnpsuv] [-o port] host
rdate displays and sets the local date and time from the host name or
address given as the argument. The time source may be an RFC 868 TCP
protocol server, which is usually implemented as a built-in service of
inetd(8), or an RFC 2030 protocol SNTP/NTP server. By default, rdate
uses the RFC 868 TCP protocol.
The options are as follows:
-4 Forces rdate to use IPv4 addresses only.
-6 Forces rdate to use IPv6 addresses only.
-a Use the adjtime(2) call to gradually skew the local time to the
remote time rather than just hopping.
-c Correct leap seconds. Sometimes required when synchronizing to
an NTP server. When synchronizing using the RFC 868 protocol,
use this option only if the server does not correctly account for
leap seconds. You can determine if you need this parameter if
you sync against an NTP server (with this parameter) or
(recommended) check with a local radio controlled watch or phone
-n Use SNTP (RFC 2030) instead of the RFC 868 time protocol.
Use port port instead of port 37.
-p Do not set, just print the remote time.
-s Do not print the time.
-u Use UDP instead of TCP as transport.
-v Verbose output. Always show the adjustment.
/var/log/wtmp record of date resets and time changes
To get the legal time in Germany, set the /etc/localtime symlink to
/usr/share/zoneinfo/right/Europe/Berlin and issue the following command:
# rdate -ncv ptbtime1.ptb.de
The command of course assumes you have a working internet connection and
DNS set up to connect to the server at Physikalisch-Technische
Bundesanstalt in Braunschweig, Germany.
To gradually adjust time once an hour after the first "step" adjustment,
put the following line into root’s crontab:
58 * * * * rdate -ncav ptbtime1.ptb.de | logger -t NTP
To to set the time through an ssh tunnel, use something like so:
ssh -f -L 10037:time.example.com:37 tyr.example.com sleep 10
rdate -a -o 10037 locahost
date(1), adjtime(2), inetd(8), ntpd(8), timed(8)
This manual page was written by Christos Zoulas. It was changed by
Anibal Monsalve Salazar for the Debian Project.