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I have a Debian server running on some hardware from ca 2004, and the real time clock is running too fast. I have set it to run ntpdate every hour, so the clock is mostly correct, but this seems kinda like a hack.

AFAIK there are a couple of reasons it could run wrong. The first is that the CMOS battery is old. But the server is always on, so I don't see why this should have any effect. The server is in a really warm room, but it's running fine, so I don't think this is the reason.

If the battery is old, can I change it without turning the server off (Hot-swappable battery)?

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Changing CMOS battery with the Machine powered on - No

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Indeed. That sounds like asking for trouble. Besides, it's not the battery that determines the pace of the clock. Have a look here. – oKtosiTe Dec 2 '10 at 18:01

As oKtosiTe said Crystal Oscillator is the thing that can get less accurate after long time. Theoretically data lines carring these clock impulses can be broken and they can lost majority of signals, but I've never seen it in real.

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Can it be done? Yes it can. Risk vs reward of static electric shock can ruin more than a 3 dollar battery causing major problems in main boards, traces in the boards etc.

I have done it under the gun on rack servers. CMOS batteries are even nowadays made to be able to hot swap because of time and advancement of bleeding edge technology. Can it be done? Yes. Should it be? Probably not.

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What's wrong with running ntpd in the background? Something like ntpd is really the only way to keep a clock in synch without some extra hardware, as far as I know.

You can use this in your /etc/ntp.conf file:


and get an NTP server that's perfectly willing to help you keep time.

But just to confirm your experience, I bought a cheapo "bare" PC in 2001, and ran it pretty much around the clock for the next 10 years. I did replace the CMOS battery once during its lifetime, which improved its clock's accuracy somewhat, but the clock gradually got worse and worse over time. I was regularly restarting ntpd the last year of its life, when ntpd decided it couldn't get back in synch and just up and quit.

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