Clock skew problem - RHEL 4 AS

[David Tonhofer]

Syed Johnullah wrote:
> I did set the time in BIOS and on OS also time zone configured
> correctly.
> I don't have problem in other servers in which 32 bit RHEL 4 ES
> installed, 
> Two  DL380 G4 servers which is Extended 64 bit has RHEL 4 ES 64 bit
> installed.
>
> Both the servers have same problem.
>
> Regards
> Syed Johnullah
>
>  
> -----Original Message-----
> From: Meadows, Andrew [mailto:AMeadows at BMI.com] 
> Sent: Wednesday, December 20, 2006 5:56 PM
> To: redhat-list at redhat.com
> Subject: Re: Clock skew problem - RHEL 4 AS
>
> If you can shutdown the server for a few moments you are golden. Just
> shut down and set the time in the bios. Also make sure on the os side
> that you have the time zone set correctly..... 
>   


Well, the 'hwclock' command should be used to set the real-time clock 
from the running OS, no need to
shutdown.

What does the NTP logfile say? If there isn't one, add "logfile 
/var/log/ntp_log" or something to "/etc/ntp.conf"

Maybe the hardware is foobared or the server is running too hot?

A comment from http://www.beaglesoft.com/mainfaqclock.htm

"The hardware clock is updated once per second and cannot display 
fractions of a second. For this reason, it cannot be read or set within 
better than a second. The accuracy of the hardware clock is determined 
by the quality of its timebase oscillator (typically a 32.768 kHz 
crystal). These crystals are economical, costing less than $1 in single 
quantities. However, they offer only marginal timekeeping performance. 
They are sensitive to temperature and other factors and are often not 
calibrated at the factory. Even under the best conditions, these 
oscillators are not likely to be stable to better than 1 part per 
million (about 0.1 seconds per day). In actual operation, most hardware 
clocks seem to gain or lose time at a rate of about 1 to 15 seconds per 
day, with 5 or 6 seconds per day being typical. Although the hardware 
clock usually outperforms the software clock by a considerable amount, 
its performance often pales in comparison to even a low-cost wristwatch."