Clock issues

[Sean Carlos]

akonstam at trinity.edu wrote:
> On Thu, Nov 10, 2005 at 06:49:01AM -0500, Bob Chiodini wrote:
> 
>>On Wed, 2005-11-09 at 10:40 -0800, Brian D. McGrew wrote:
>>
>>>Running a Dell PE850 with FC4 installed.  I used rdate -s to set the
>>>clock and the time is correct.  I even have it in the crontab tab.
>>>
>>>When the machine reboots, the clock is wrong, way wrong by anywhere from
>>>6 to 12 hours.  How do I get the clock to sync up at reboot time?
>>>
>>>-brian
>>>
>>>Brian D. McGrew { brian at visionpro.com || brian at doubledimension.com }
>>>--
>>>
>>>>Those of you who think you know it all,
>>>
>>>  really annoy those of us who do! 
>>>
>>
>>Brian,
>>
>>Are you cleanly rebooting the system?
>>
>>/etc/init.d/halt contains code to set the hardware clock to the system
>>(software) clock.  Unless the motherboard battery is failing, or the
>>system was not properly shutdown/rebooted the H/W clock should not drift
>>that much.
>>
>>Running rdate from cron only sets the system clock, not the H/W clock.
>>You should also run hwclock --systohc in the same cron job.
>>
>>As suggested by Yonas and Alexander, NTP is another solution, but it
>>will not correct the H/W clock by itself.  You still must insure that
>>hwclock runs, either periodically, or at shutdown.
>>
>>What is the BIOS time immediately after shutting down?
>>
>>
>>Bob...
> 
> This is a periodic problem that someone down here was complaining about
> just today. When you boo t hwclock is run to set the system clock to
> the hardware clock. That code is in /etc/rc.d/rcsysinit
> 
> When you halt hwclock is run to reverse the process. That code is in
> /etc/init.d/halt.
> 
> Check to see that the running of the hwclock -systohc and
> hwclock -hctosys both run correctly. Further check whether the hwclock is
> drifting due to a weak battery.

I also had this problem on two different Dell desktops.

For one (Dimension 4700), the solution was discussed here:

https://www.redhat.com/archives/fedora-list/2005-April/msg04936.html

If

[root at localhost ~]# hwclock --systohc
select() to /dev/rtc to wait for clock tick timed out

does not work but

[root at localhost ~]# hwclock --systohc --directisa

works,

then add a

CLOCKFLAGS=--directisa

line to the /etc/sysconfig/clock file.  Look at /etc/rc.d/init.d/halt at
around line 115 to see how that works.

For a Dimension 8400? the solution was to add

dev.rtc.max-user-freq = 1024

to /etc/sysctl.conf

Sean