[lug] Linux clock loses time

D. Stimits stimits at attbi.com
Thu Mar 13 14:17:19 MST 2003

Dan Julio wrote:

> Hey All,
> I inherited a Dell Inspiron 4100 running Redhat Linux
> 7.3 (version 2.4.18-3).  When the machine is running
> Linux it loses about 5 minutes every 8 hours of
> runtime.  When the machine is off the RTC keeps time
> perfectly.  I verified this by setting it and then
> shutting down Linux.  When I booted several days later
> the RTC shown at the BIOS level and also when Linux
> booted was right on.
> Does anyone have an idea of why this might be?

Recently...maybe on this list, or on a newsgroup, I don't recall 
which...someone mentioned exactly what is going on in this situation. 
Apparently when linux has had its time set at one particular moment, and 
then it is set again at some later date, linux remembers how much change 
was asked for, and the period of time over which that change occurred. 
It then self-adjusts based on that drift rate. So if you set the time, 
then set it again a week later, and perhaps again another week later, 
running linux should actually improve timing accuracy. Maybe if it is 
off a lot, then adjust it once a day until drift improves...after that 
once a week. If you dual boot and adjust from another o/s, it'll 
probably work against you instead of for you. Ditto for adjusting the 
clock from the BIOS. Personally I do not know how well this works, but 
it is logical, might be interesting to see if daily adjustments lead 
eventually to less adjustment each day (or weekly).

D. Stimits, stimits AT attbi DOT com

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