Provided by: htpdate_1.2.1-1_amd64 bug

NAME

       htpdate - Time synchronization (daemon)

SYNOPSIS

       htpdate  [-046abdhlqstxD]  [-i  pid  file]  [-m  minpoll]  [-M maxpoll] [-p precision] [-P
       <proxyserver>[:port]] [-u user[:group]] <host[:port]> ...

DESCRIPTION

       The HTTP Time Protocol (HTP) is used to synchronize a computer's time with web servers  as
       reference  time  source.  Htp will synchronize your computer's time to Greenwich Mean Time
       (GMT) via HTTP headers from web servers.  The  htpdate  package  includes  a  program  for
       retrieving  the  date  and  time from remote machines via a network. Htpdate works through
       proxy servers. Accuracy of htpdate  will  be  usually  within  0.5  seconds  (better  with
       multiple servers). If this is not good enough for you, try the ntpd package.

OPTIONS

       -0     HTTP/1.0 request (default is HTTP/1.1).

       -4     Force  IPv4  name  resolution only. Default behaviour is to try IPv6 first and fall
              back to IPv4.

       -6     Force IPv6 name resolution only.

       -a     Adjust time smoothly (default in daemon mode).

       -b     Burst mode uses multiple polls for each web server to enhance accuracy.

       -d     Turn debug on. Shows the "raw" timestamp, round trip time, time delta and and basic
              statistics of web server responses. Useful to determining the quality of a specific
              web server as time source.

       -h     Show help.

       -i     Set the pid file (default /var/run/htpdate.pid).

       -l     Use syslog for output (levels LOG_WARNING and  LOG_INFO).  Convenient  if  you  use
              htpdate from cron.

       -m -M  These  options  specify the minimum (-m) and maximum (-M) polling intervals for HTP
              requests, in seconds. The default range is between 30 minutes and 32 hours. Htpdate
              calculates  the  optimal polling frequency between minimum and maximum values. Only
              applicable when running in daemon mode.

       -p     Precision (in milliseconds) specifies the operating accuracy of htpdate. Internally
              htpdate  uses  a  different  algorithm  to  detect a time offset, when precision is
              specified. Precision only has effect in daemon mode. Use with caution.

       -q     Query web server and display time, but do not change time (default  in  interactive
              mode).

       -s     Set time immediate. In daemon mode -s only applies the first poll.

       -t     Turn  off  sanity time check. By default a time offset larger than a year, compared
              to current localtime, is rejected. With -t set, any time stamp will be accepted.

       -u     Set the user and group that the server normally runs at (default is root).

       -x     Let htpdate compensate for the systematisch clock drift.

       -D     Run as daemon (requires root privileges).

       -P     Proxy server hostname or ip-address.

       host   Web server hostname or ip-address. Up to 16 hosts may be specified, but in  general
              3 to 5 hosts should be enough for a redundant and accurate setup.

       port   Portnumber (default 80 and 8080 for proxy server)

EXAMPLES

       Request time from web server (don't update local clock):
              htpdate -q www.linux.org www.freebsd.org

       Verbose output (don't update local clock):
              htpdate -d -q www.linux.org www.freebsd.org

       Adjust time smoothly and log output to syslog (eg. cron):
              htpdate -a -l www.linux.org www.freebsd.org

       HTTP/1.0 request in IPv6 literal format (RFC 2732):
              htpdate -0 [2001:DB8:1af6::123]:80

       Run htpdate as daemon:
              htpdate -D www.linux.org www.freebsd.org

       Daemon mode for the security minded:
              htpdate -D -u nobody:nogroup www.linux.org www.freebsd.org

AUTHOR

       Eddy Vervest <eddy@vervest.org>, http://www.vervest.org/htp

SEE ALSO

       rdate, timed, ntpd, adjtimex, ntp_adjtime,
       HTP implementation by Roy Keene (http://www.rkeene.org/oss/htp/)