HTPDATE(8)HTPDATE(8)NAMEhtpdate - Time synchronization (daemon)
SYNOPSIShtpdate [-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). Conve‐
nient 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 causion.
-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. Upto 16 hosts may be speci‐
fied, but in general 3 to 5 hosts should be enough for a redun‐
dant 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/)
htpdate version 1.1.2 HTPDATE(8)
