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Re: system time has change while installing

On Thu, Jun 20, 2013 at 01:36:02PM +0400, Konstantin Khomoutov wrote:
> > Why is UTC time bogus?
> Well, I am simply afraid of a possible knee-jerk reaction of an admin
> who for whatever reason manages to hit the BIOS setup program and sees
> martian time there, which they would likely attempt to "fix".
> I mean, keeping the time, which BIOS thinks is local, as UTC is
> certainly possible but it requires implementing a policy, so that
> everyone managing such a machine should be trained to keep that in mind.

The training is simple: use NTP, on every single machine, always.  If
the time is off this means your network or NTP client is down.  The RTC
clock is needed only during boot-up.

> Now imagine a heterogenous environment (as I do have at my $dayjob)
> where there's lots of Windows machines and a number of Debian (and
> other Linux-based) machines.  I positively see no reason to introduce
> distinctions between these boxes with regard to their BIOS time.
> This is really an "implementation detail".
> IMO, putting a string "LOCAL" to the /etc/adjtime file is way less
> hassle to carry out than implementing a policy and training admins.

Except, there's a laundry list of possible breakage caused by RTC using the
local time when DST changes are involved.

> For a bedroom x86 machine, keeping its BIOS time as UTC is perfectly
> acceptable as it usually has zero to one administrators.

I'd say, it's only bedroom machines (and sometimes student labs) that dual
boot Windows with other systems.  On a server, you really don't want sudden
failure, possibly with data loss, to happen if it's rebooted during one of
those four hours a year[1].  Failures I've read about that did not involve
a reboot at that time all had Windows involved somehow, so I hope during
the remaining 8762 hours you should be safe.

Still, off hours are when you tend to do maintenance, and you don't want
a leisure upgrade to become an urgent search for backups.

[1]. Usually, a particular problem applies to only one of those hours, but
with different issues in mind all four are at risk.


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