[Dovecot] Time just moved backwards
dovecot-20061108 at billmail.scconsult.com
Mon Apr 9 00:20:39 EEST 2007
At 12:03 PM -0700 4/8/07, Sean Kamath wrote:
>It's not just dovecot, by the way. MANY things don't like have time
>move backward, like Cron, at, etc.
>You should *NEVER* have the clock jump back in time (except during
>DST changes -- yuk).
DST changes (at least on sane systems) do not change the system clock
time. Time zones are a cosmetic feature, i.e. how humans are shown a
description of time. For example, the following are different ways
of displaying exactly the same time:
12:03 PM -0700 4/8/07
15:03 PM EDT 4/8/07
14:03 PM EST 4/8/07
19:03 PM -0000 4/8/07
00:03 PM +0500 4/9/07
>The correct way to handle time on Unix systems is to set the clock
>at boot (rdate, ntpdate, etc), and then *skew* the clock, so time
>slows down to match the right time. It can always jump forward, but
>NTP only jumps by a (settable) maximum amount per time-quantum.
>This prevents things like make, and NFS caching, and a bunch of
>other stuff "just work".
>As far as I know, all shipping OSes now have a working NTP client,
>and it's VERY easy to just add
>to the ntpd.conf file, and you're good to go on reboot.
It is important for people to understand how much simpler it is now
to run basically functional and non-abusive NTP than it was even 5
years ago. The work put into making pool.ntp.org usable has
essentially eliminated the need to think much about NTP for most
bill at scconsult.com
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