On 02/05/2017 11:58 AM, J Martin Rushton wrote:
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
So, if I understand the man page, this command should be the first one
in /etc/ntp.conf
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