[lug] Linux clock loses time

Zan Lynx zlynx at acm.org
Thu Mar 13 14:20:27 MST 2003

On Thu, 2003-03-13 at 14:17, D. Stimits wrote:
> 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).

If you have a network connection for this computer, run ntpd and never
worry about inaccurate time again!  It's nice.

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