NAME

       rdate - set the system's date from a remote host

SYNOPSIS

       rdate [-46acnpsuv] [-b sec] [-o port] [-t msec] host

DESCRIPTION

       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 5905 protocol SNTP/NTP server. By default, rdate uses the RFC 868 TCP protocol.

       OpenRdate supports IPv4 and IPv6 protocols.

OPTIONS

       -4     Force rdate to use IPv4 addresses only.

       -6     Force 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.

       -b sec Use adjtime if clock difference is at most sec seconds or hop if difference is  greater.  This  is
              the same as including of removing the option -a, based on clock difference.

       -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 service.

       -n     Use SNTP (old RFC 2030, currently RFC 5905) instead of the RFC 868 time protocol. SNTP will always
              use UDP protocol and its default port is 123.

       -o port
              Use port 'port' instead of port 37 (RFC 868) or 123 (SNTP, RFC 5905).

       -p     Do not set, just print the remote time.

       -s     Do not print the time.

       -u     Use UDP instead of TCP as transport (for RFC 868 only; see -n option).

       -t msec
              Does not set time if it took more than msec milliseconds to fetch time from network.

       -v     Verbose output. Always show the adjustment.

FILES

       /var/log/wtmp
              Record of date resets and time changes.

EXAMPLES

       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 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 localhost

SEE ALSO

       date(1), adjtime(2), inetd(8), ntpd(8), ntpdate(8), timed(8)

AUTHORS

       OpenRdate was originally developed by David Snyder and was based in rdate, created by Christos Zoulas  in
       1994 for OpenBSD Project. Over time, OpenRdate got several contributions from people.

       This manual page was written by Christos Zoulas. It was changed by Anibal Monsalve Salazar for the Debian
       Project and updated by Joao Eriberto Mota Filho.