[ntp:questions] ntpd and the CMOS clock

Juergen Beisert juergen at kreuzholzen.de
Mon Aug 10 08:28:50 UTC 2009


Hi list,

I'm not sure if this is really an ntpd related question. But my CMOS clock 
problem only occurs when the ntpd is also running.

My ntpd gets the time from a DCF77 radio receiver. I can manually sync the 
system time and the CMOS time and everything is fine:

$ date; hwclock -u
Mon Aug 10 03:53:20 CEST 2009
Mon Aug 10 03:53:20 2009  0.000000 seconds

But after a few hours this happens (I ran "date; hwclock -u" every 5 minutes 
with the help of the 'watch' command):

[...]
Mon Aug 10 03:58:20 CEST 2009
Mon Aug 10 03:58:20 2009  0.000000 seconds

Mon Aug 10 04:03:20 CEST 2009
Sun Aug  9 22:03:20 2009  0.000000 seconds  <--- bang!
[...]

I did a look into the Linux kernel sources and they only are setting minutes 
and seconds in the CMOS clock every 11 minutes. But not the hours. But who is 
setting the hour in my case? The ntpd?

Any idea?

Regards
Juergen



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