Re: HWclock y la hora del sistema
Pues he ido a mirar a la lista de bugs del paquete de marras y esto
es lo que me he encontrado, que ya hay un aviso sobre el cambio en el
script de inicialización.
Si tal me callo, pues estoy de acuerdo completamente con el autor del
mensaje.
--
Saudos:
><ose xmanoel@i.am (Vigo/Galicia/España)
http://pagina.de/xmanoel/
http://w3.to/mikkeli/
Debian bug report logs - #37657
util-linux: hwclock --systohc dangerous
Package: util-linux; Severity: important; Reported by:
pimlott@idiomtech.com; dated Fri, 14 May 1999 06:33:00 GMT; Maintainer for
util-linux is Vincent Renardias <vincent@debian.org>.
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Date: Fri, 7 May 1999 16:56:02 -0400 (EDT)
To: submit@bugs.debian.org
Subject: util-linux: hwclock --systohc dangerous
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X-Mailer: bug 3.1.7
Package: util-linux
Version: 2.9i-1
Severity: important
[This is a resend--my first report was never acknowledged. Sorry if you
get a duplicate.]
I believe that the "hwclock --adjust" in the hwclock startup script and the
"hwclock --systohc" in the shutdown script have considerable potential for
harm, and should be removed from the default installation of Debian.
First, suppose that I notice that my hardware clock and system clock are
both off by one hour, I use "hwclock --set" to correct the hardware clock.
Since I don't want my system time to change discontinuously, I do not change
my system time. Instead, I reboot cleanly for the new time to take effect.
On shutdown, however, the hardware clock is set back to the system clock,
effectively undoing my action.
Second, suppose that I notice that my hardware clock is wrong, but instead
of changing it with hwclock, I shut down and change it via a BIOS menu, or
DOS. Now, when I boot, "hwclock --adjust" will be confused about how much
time has passed since the last adjustment and make an incorrect adjustment.
Finally (and this one I'm not so sure about), every time the hardware clock
is set (even with "hwclock --systohc"), hwclock writes drift information to
/etc/adjtime. In the first case above, the clock was changed twice, both of
which might have appeared to hwclock as huge drifts, which would mess up the
clock the next time the system is restarted and "hwclock --adjust" is run.
I believe hwclock does have some logic to detect large time jumps and not
treat them as drifts, but I know that things can go wrong because they have
with my system (my /etc/adjtime file had a drift of 2796.258301 seconds/day
after I recently played with the clock).
In short, these mechanisms are not reliable unless the user understands how
they work. By putting them in place without the user's knowledge, you
subject him to several pitfalls. Time is too important for this. Better
the clock be inaccurate in a simple and predictable way.
If you have thought this through and don't consider it a problem, please
share the reasons.
Thanks,
Andrew
-- System Information
Debian Release: potato
Kernel Version: Linux nolfolan 2.2.7 #1 Fri Apr 30 07:54:26 EDT 1999 i686 unknown
Versions of the packages util-linux depends on:
ii libc6 2.1.1-2 GNU C Library: Shared libraries and timezone
ii libncurses4 4.2-3.2 Shared libraries for terminal handling
ii slang1 1.2.2-2 The S-Lang programming library - runtime ver
ii slang1 1.2.2-2 The S-Lang programming library - runtime ver
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Acknowledgement sent to pimlott@idiomtech.com:
New bug report received and forwarded. Copy sent to Vincent Renardias
<vincent@debian.org>. Full text available.
----------------------------------------------------------------------------
Report forwarded to debian-bugs-dist@lists.debian.org, Vincent Renardias
<vincent@debian.org>:
Bug#37657; Package util-linux. Full text available.
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Ian Jackson / owner@bugs.debian.org, through the Debian bug database
Last modified: 00:39:01 GMT Thu 24 Jun (timestamp page available).
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