16.5 Hardware Clock Drift
The hwclock command provides the interface to the hardware clock. If you are wanting to ensure the correct time then with a default Debian set up it is recommended that you use ntp instead if you can. When you reboot the system will save the current correct time to the hardware clock.
--adjust option of the hwclock command checks
information stored in the configuration file
/etc/adjtime and makes
an actual correction to the time stored in the hardware clock to
account for the drift that it (the hwclock utility) has been
monitoring. (Each time you set the hardware clock with the
hwclock command the current time is compared to the previous time
it was corrected to determine the amount of drift.) Thus, when setting
the system clock from the hardware clock it is advisable to do the
$ sudo hwclock --adjust $ sudo hwclock --hctosys
When updating the hardware clock from an accurate system clock do:
$ sudo hwclock --systohc
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