Mailinglist Archive: opensuse-de (5189 mails)

[bock@xxxxxxxx (Andreas Bock)]

Andreas Bock schrieb:

> Wahrscheinlich doch nicht.
Berichtigung: Ist nicht das gleiche.
 --hctosys schreibt die HW-uhr in die Systemzeit.
 --adjust berechnet die Zeitdrift der HW-Uhr gegenüber der System-Zeit
und passt dieHW-Uhr an.

man hwclock:
[schnipp]
The Adjust Function
       The Hardware Clock is usually not very accurate.  However,
       much of its inaccuracy is  completely  predictable  --  it
       gains or loses the same amount of time every day.  This is
       called systematic drift.  Hwclock's "adjust" function lets
       you  make systematic corrections to correct the systematic
       drift.

       It works like this: Hwclock keeps  a  file,  /etc/adjtime,
       that  keeps  some  historical information.  This is called
       the adjtime file.

       Suppose you start with  no  adjtime  file.   You  issue  a
       hwclock  --set  command  to  set the Hardware Clock to the
       true current time.  Hwclock creates the adjtime  file  and
       records  in it the current time as the last time the clock  
       was calibrated.  5 days later, the  clock  has  gained  10
       seconds, so you issue another hwclock --set command to set
       it back 10 seconds.  Hwclock updates the adjtime  file  to
       show the current time as the last time the clock was cali-
       brated, and records 2 seconds per day  as  the  systematic
       drift  rate.  24 hours go by, and then you issue a hwclock
       --adjust command.  Hwclock consults the adjtime  file  and
       sees  that  the  clock  gains  2 seconds per day when left
       alone and that it has been left alone for exactly one day.
       So  it  subtracts  2  seconds from the Hardware Clock.  It
       then records the current time as the last time  the  clock
       was  adjusted.   Another  24  hours  goes by and you issue
       another hwclock --adjust.  Hwclock does  the  same  thing:
       subtracts  2 seconds and updates the adjtime file with the
       current time as the last time the clock was adjusted.

       Every time you calibrate (set) the clock, hwclock recalcu-
       lates  the  systematic drift rate based on how long it has
       been since the last calibration,  how  long  it  has  been
       since  the last adjustment, what drift rate was assumed in
       any intervening adjustments, and the amount by  which  the
       clock is presently off.

       A  small  amount  of error creeps in any time hwclock sets
       the clock, so it refrains from making an  adjustment  that
       would  be  less than 1 second.  Later on, when you request
       an adjustment again, the accumulated drift  will  be  more
       than a second and hwclock will do the adjustment then. 
[end schnipp]

Andreas

---------------------------------------------------------------------
To unsubscribe, e-mail: suse-linux-unsubscribe@xxxxxxxx
For additional commands, e-mail: suse-linux-help@xxxxxxxx