On 05/02/17 16:15, Richard wrote: > >> Date: Sunday, February 05, 2017 10:26:05 -0500 >> From: Robert Moskowitz <rgm@xxxxxxxxxxxxxxx> >> >> I have read: >> http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences-bet >> ween-ntpd-and-chronyd/ >> >> My server is up all the time and will serve time to internal >> systems (via DHCP options). >> >> Caveat is that my server is an armv7 (Cubieboard2) which does not >> have an RTC (no battery). So whenever the system boots, the time >> is ZERO (Dec 31, 1969 or some such). >> >> Chrony fixes this really fast; shortly after boot the time is good. >> Chrony CAN be configed as an internal time server. But chrony does >> not seem to step the clock for any adjustments needed. It is more >> important that this systems time be right all the time than to >> avoid clock steps. >> >> This brings me back to NTP, which normally takes hours to bring the >> time from ZERO to current, but keeps the time correct. >> >> So: >> >> Can Chrony check the time, say once a day? >> >> Or can NTP make a BIG time jump all at once (on system restart)? > > Where I have somewhat similar issues, I have historically used a > crontab "@reboot" entry to call ntpdate which gets the clock set > correctly. From there ntp keeps it in sync. > > This can now be accomplished with ntpd, and ntpdate is threatened > with depreciation/retirement. See the top of the ntpdate man page for > more details. > The NTP configuration option you may be after is "tinker panic 0" which allows NTP to make big jumps as often as required. See ntp_misc(5). There is a related discussion with making VMs take big jumps at https://www.centos.org/forums/viewtopic.php?f=16&t=61186&p=258254#p258254
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