Carlos E. R. wrote:
On 2011-07-15 23:09, Per Jessen wrote:
Carlos E. R. wrote:
On 2011-07-15 21:14, Anton Aylward wrote:
NTP does that. It has the hardware clock as a reference in place or a remote server reference and knows the rate of drift of the hardware clock.
Of the hardware clock, no. Of the system clock, yes.
No, the drift is the inaccuracy or error of the clock frequency, i.e. of the hardware oscillator. By knowing the drift of the hardware clock, ntp is able to massage the system clock.
You are confusing names.
There are two clocks.
1) The hardware clock, aka cmos clock, aka battery backed clock. It is the only one that can run when the system is powered down.
2) The system clock. It is controlled by the CPU, with different hardware types. AKA software clock. It only runs with the system up.
Even if there is hardware involved in clock #2, it is not called "hardware clock".
Both clocks have different drifts, taken into account differently. #1 by hwclock, #2 by ntp. Don't mix names!
man ntp.conf: driftfile This command specifies the complete path and name of the file used to record the frequency of the local clock oscillator.
When the system boots, clock #1 is read, its drift calculated, and then clock #2 is set up with the result. This is done via scripts and hwclock. When the system runs, #1 is not used at all. Time is read from #2 only, and its drift is corrected by NTP (if available). When the system goes down, the system ensures that clock #1 is adjusted, and its drift calculated and noted.
AFAIR, ntp updates the drift file once an hour. -- Per Jessen, Zürich (15.6°C) -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org