I have read: http://thegeekdiary.com/centos-rhel-7-chrony-vs-ntp-differences-between-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)? thanks
> Date: Sunday, February 05, 2017 10:26:05 -0500 > From: Robert Moskowitz <rgm at htt-consult.com> > > 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.
On 05/02/17 16:15, Richard wrote:> >> Date: Sunday, February 05, 2017 10:26:05 -0500 >> From: Robert Moskowitz <rgm at htt-consult.com> >> >> 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 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: OpenPGP digital signature URL: <http://lists.centos.org/pipermail/centos/attachments/20170205/5cad9399/attachment-0001.sig>