Re: [chrony-users] Intermittent network access even at boot

[Bill Unruh <unruh@xxxxxxxxxxxxxx>]

On Wed, 28 Mar 2012, Wickham, Mark wrote:

> Hello,
>
> I am working on a line of Linux products that have an RTC with no battery, so it returns to Jan 1970 every time it is powered off/on.  After attempting to use openntpd for a while, we see that Chrony is a much better fit.  Our device may run without network for long times, even at boot time, and so we need some way for the device to start up, and get time later.

So why do you have the rtc at all? What does it do for you if it cannot keep
the time.

> Hanging within the startup scripts is not acceptable because we have other daemons that also need to be started, whether or not we have a network.

There is an extensive documentation in chrony.txt of  putting a network source
offline and online again when the network comes up again. 
Mind you it will be impossible to set the time to anything except 1970 until
something comes up. Either that or put a battery into your rtcs.

Note that you could look for the latest files ( eg in /var/log/ ) and use
their time as a better approximation of the current time than 1970.


> The README indicates that if DNS is not available at startup, it will not be consulted later.  Is this still the case?

No. You tell the system when the network comes up to put the sources online
via chronyc.


> Do you have any patches or suggestions for making Chrony capable of running in a truly intermittent network environment?

Curnoe developed chrony precisely for this scenario. He had a modem on his
computer, and could not connect to any network except occasionally during the
day.


> Thanks in advance for any help.
>
> Mark Wickham
> Senior Principal Software Engineer
>
> Digi International(r)
> 11001 Bren Road E
> Minnetonka, MN 55343
>
> Direct: 952 912 3353
> Main: 952 912 3444
> Email: Mark.Wickham@xxxxxxxx
>
> www.digi.com<http://www.digi.com/>

--
William G. Unruh   |  Canadian Institute for|     Tel: +1(604)822-3273
Physics&Astronomy  |     Advanced Research  |     Fax: +1(604)822-5324
UBC, Vancouver,BC  |   Program in Cosmology |     unruh@xxxxxxxxxxxxxx
Canada V6T 1Z1     |      and Gravity       |  www.theory.physics.ubc.ca/

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