[CentOS] System Time Source

Wed May 24 14:14:26 UTC 2017
Robert Moskowitz <rgm at htt-consult.com>

On 05/24/2017 09:53 AM, Chris Olson wrote:
> One of our STEM interns recently observed that there are
> inexpensive clocks that sync via radio to standard time
> services.  This begged a question about why every computer
> would not have a radio module to receive time.  Our senior
> staff did not have a good answer or if time from such a
> radio module would be supported by the operating system.
> When I was a student, such questions would have earned me
> extra homework assignments.  We now have only PC directed
> relationships with interns so we don't assign any extra
> homework for curiosity.  Can anyone help with the answers?
> Thanks and best regards.

It costs more to add a radio than an RTC and battery and get time from 
any of the Internet NTP time servers.  Plus you then have to put the 
computer where the radio will receive the signal.

I can't tell you how many clocks I have seen with the wrong time because 
they are not getting the radio signal.  It shows right on the clock face 
of no radio signal.

If you have Internet, you have NTP.

In fact most ARM SOCs are without RTC and depend on the Internet for 
time.  Chrony works really well to make the quick jump at startup to get 
the time right.  ntp itself can take too much time to step a system to 
the current time.

I have done a bit of research into configuring chrony for a system 
without an RTC.  See my guide at: