[systemd-devel] RTC on BeagleBone Black or embedded platforms

Lennart Poettering lennart at poettering.net
Fri Feb 28 04:02:41 PST 2014

On Fri, 28.02.14 11:13, Koen Kooi (koen at dominion.thruhere.net) wrote:

> Op 27 feb. 2014, om 18:56 heeft Lennart Poettering <lennart at poettering.net> het volgende geschreven:
> > On Thu, 27.02.14 10:46, Mike (bellyacres at gmail.com) wrote:
> > 
> > Heya,
> > 
> >> My biggest dilemma at this time right now is with the RTC.  The
> >> BeagleBone Black does have a RTC and it gets assigned to /dev/rtc0.
> >> There is however no battery backup for this device.  I've added a
> > 
> > Hmm, what's the point of such an RTC? I mean, Linux uses an RTC only to
> > initialize the system clock from and then never looks at it again. But
> > if the RTC has no battery it's entirely pointless to ever look at it, so
> > what is an RTC good for that has no battery?
> To prevent clock-drift, the RTC does a better job at that than the
> kernel. 

Hmm, but that sounds more like theory than practice. I mean, how would
you even use this in Linux? As mentioned, Linux only initialized the
system clock from the RTC and otherwise doesn't care at all anymore...

> Personally, I just have my DHCP server provide an ntp entry
> and have connman do its ntp thing :)

Yupp, that sounds like the much better deal. If people care about
correct clocks they should use NTP.


Lennart Poettering, Red Hat

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