Mailinglist Archive: opensuse (3156 mails)

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Re: [opensuse] ntp can not manage to put the clock in sync.
  • From: Aaron Kulkis <akulkis00@xxxxxxxxxx>
  • Date: Thu, 06 Dec 2007 00:18:29 -0500
  • Message-id: <47578625.8090300@xxxxxxxxxx>
Billie Walsh wrote:
Somewhere in the past I read that computers are wonderful machines.
Capable of great things. BUT, they are horrible clocks.

The way it was explained was that when system use was high and resources
were strained the clock was the last thing to get updated. Thus, it
looses time. I'm sure it isn't near the problem it was many years ago
but if your a power user it still could be a problem.

This is precisely why NTP was invented -- it solves this
problem by obtaining time from calibrated time servers,
and also takes into account network latency. Level 0
sources are atomic clocks (such as run by the US Naval
Observatory -- navies have VERY high interest in extremely
accurate timekeeping because accurate navigation depends
on it), Level 1 sources obtain their time from Level 0
sources, Level 2 from Level 1, etc. Most Level 0 and
Level 1 sources are not for use by the general public.

Level 1 sources prefer that only 1 or a very very small
percentage (like 1 in a 1000) of an organization's
machines get time from the Level 1, and then use
those hosts as Level 2 time hosts, which are then
to serve the rest of the organization.

Do not under ANY circumstances get NTP time from
a Level 0 time server without explicit permission
from whoever owns or has the responsibility of
operating it. If you need a level 0 time server,
then you can get a device which recieves a radio
signal from a US Navy Observatory, and connects
to a communications port in your computer. These
tend to run in the US $100 - $200 range, and will
provide time accurate within 1 microsecond.

In most NTP configuration files, the CMOS clock on the
motherboard is rated as level 10 (kind of a "last resort").
I have no idea why onboard CMOS clocks are less
accurate than a US $5 wristwatch which includes an
LCD display in that price.

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