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Date: Tue, 30 Oct 2001 09:39:13 -0600
From: Tim Walberg <twalberg@mindspring.com>
To: GOMBAS Gabor <gombasg@inf.elte.hu>
Cc: Tim Walberg <twalberg@mindspring.com>, linux-kernel@vger.kernel.org
Subject: Re: Nasty suprise with uptime
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In-Reply-To: <20011030154733.B27230@pandora.inf.elte.hu> from GOMBAS Gabor on 10/30/2001 08:47
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Hmm... ever hear of NTP? My general rule of thumb:
Never trust any CMOS clock; let the kernel keep track
of time and periodically update the CMOS clock so
that you (hopefully) get a reasonable starting point
when you boot. Trusting any clock with a cheap power
source to provide accurate time-keeping is an exercise
in futility... (and it's not necessarily the power
source's fault - even an outrageously expensive power
source doesn't guarantee good time-keeping). I think
of a CMOS clock as kind of a book mark. If the book
mark gets lost, I can still find where I left off,
it just takes a little more work.


			tw

On 10/30/2001 15:47 +0100, GOMBAS Gabor wrote:
>>	On Tue, Oct 30, 2001 at 07:50:43AM -0600, Tim Walberg wrote:
>>=09
>>	> Wouldn't it be fairly simple for the kernel to just remember the (wall
>>	> clock) time at boot, and uptime just subtract that from the current
>>	> (wall clock) time?
>>=09
>>	So every people with faulty CMOS batteries would have 30+ years of
>>	uptime. And if the CMOS date is ahead of the real one and the admin
>>	sets it back, you will get negative uptimes etc. If you want such
>>	amusements, it is far easier to write an uptime program that just calls
>>	random() instead of asking the kernel :)
>>=09
>>	Gabor
>>=09
>>	--=20
>>	Gabor Gombas                                       Eotvos Lorand Univers=
ity
>>	E-mail: gombasg@inf.elte.hu                        Hungary
End of included message



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