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Fedora time bug

© December 2005 Anthony Lawrence

The question of setting time comes up frequently. Setting the timezone and the system clock can be confusing, particularly if the machine is dual boot. Nowadays I don't see too many of those (a sign that Linux has grown up enough or just that it's cheap enough to run separate machines?), so the answer is usually simple: set the hardware clock to UTC, run ntpd and set your timezone correctly. But for those who want to understand how everything works, How Linux Keeps Track of Time has all the details. Linux, Clocks, and Time is also a useful summary.

So when a local reseller called recently saying he couldn't get a Fedora Core 4 box to hold time upon reboot, I assumed he just didn't have things set right and referred him to the docs.

I was wrong. The next thing I heard from the reseller was that he had found a fix.

Apparently there is a current bug with some Intel motherboards: FC3 breaks hwclock functionality on Dell PowerEdge SC420. To fix, you don't use UTC on the hardware clock, and you add CLOCKFLAGS=--directisa to the /etc/sysconfig/clock file.

I'm not sure where he found that, and am actually surprised that he did. Googling for anything time related turns up thousands of "hwclock" man pages and duplicates of the LDP docs; it's hard to sort through all that and find a problem like this. The final comment he had was:

All is working fine now.  I think the only problem is that when
daylight savings hits, the customer will have to update the bios
and the Linux date separately.

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Wed Dec 7 14:54:47 2005: 1413   BigDumbDinosaur

I think the only problem is that when daylight savings hits, the customer will have to update the bios and the Linux date separately.

Huh? UTC has no daylight savings time concept, so why would the CMOS clock have to be changed? The switch from standard to daylight and back is something that the kernel would handle.

Wed Dec 7 14:59:03 2005: 1414   TonyLawrence

But it's not set to UTC with this fix.

Thu Dec 8 17:15:19 2005: 1415   BigDumbDInosaur

Oops! Guess that part of the story didn't sink in. <Sheepish...er...dinosaurish Grin>

Tue Mar 6 04:41:18 2007: 2900   anonymous

I am having this same problem on my machine here, not intel. I came to the same conclusion independently to put CLOCKFLAGS=--directisa in /etc/sysconfig/clock.

For some reason the /dev/rtc is not working on FC6 for some machines. I noticed that when i loaded an older kernel with the "rescue disk" that hwclock works fine. I think this is a real bug that has not bubbled to the surface yet.


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