[CentOS] Chrony vd NTP

[Robert Moskowitz]

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 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

So, if I understand the man page, this command should be the first one 
in /etc/ntp.conf