[ntp:questions] Re: time reset, syncronisation lost and Large PPM values

Johan Swenker no_spam_please at swenker.xs4all.nl
Tue Nov 1 00:33:39 UTC 2005


On Sun, 23 Oct 2005 14:18:43 +0000, Tom Smith wrote:

> mike wrote:
>> The explanation is that the kernel also keeps a frequency drift value
>> that is persistent across boots. It is kept in /etc/adjtime. If this
>> file exists in your implementation, just removing it might be the 
>> answer. It fixed my problem.
>> 
> 
> Interesting. Hadn't run into that one (yet). Maybe setting the contents
> of the drift file to "0.000" instead of deleting the file would also
> get around that hickup, if that (or something similar) is, in fact,
> the problem.

You should REMOVE adjtimex and it's configuration file from your system or
at least prevent it from starting. The reason is twofold:
1) you have ntpd, which is much better at keeping a reasonable time
2) adjtimex uses an obsolete parameter in a systemcall. Unfortunately
it does have an effect: it set's the kernel variable STA_CLK. This is
interpreted by ntpd: don't mess with the clock, some other program handles
the clock. [At least this happens on Linux kernel 2.4.20 with the PPS and
NANO patches of Ulrich. And yes I have been bitten by this feature.] 

Regards, Johan Swenker




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