Re: Setting The System Clock [Linux]

From: Villy Kruse (vek_at_station02.ohout.pharmapartners.nl)
Date: 11/03/03 

Date: 03 Nov 2003 08:50:33 GMT

On Sat, 1 Nov 2003 10:59:57 +0000 (UTC),
    Bill Unruh <unruh@string.physics.ubc.ca> wrote:

>John Hasler <john@dhh.gt.org> writes:
>
>]Bill Unruh writes:
>
>]> chrony assumes that the local clock is in UTC...
>
>Yes, but chrony also corrects for your rtc errors. Thus chrony will look
>at your rtc, discover that it is 8 hours ( 8*3600 sec) out, and correct
>for this. Thus when you boot up and run chrony -r -s, it will look in
>/etc/chrony.rtc, see that your real time clock is 28800 sec out, read
>the rtc, subtract 28800 sec, and set your Linux system time to that.
>
>Windows of course has no such mechanism, so it will read the rtc, assume
>it is on local time, (which it will be) and display that time.
>
>
>
>]From the Chrony manual:
>
>]rtconutc
>]--------
>
>] `chronyd' assumes by default that the real time clock (RTC) keeps
>]local time (including any daylight saving changes). This is convenient
>]on PCs running Linux which are dual-booted with DOS or Windows.
>
>] NOTE : IF YOU KEEP THE REAL TIME CLOCK ON LOCAL TIME AND YOUR
>]COMPUTER IS OFF WHEN DAYLIGHT SAVING (SUMMER TIME) STARTS OR ENDS, THE
>]COMPUTER'S SYSTEM TIME WILL BE ONE HOUR IN ERROR WHEN YOU NEXT BOOT AND
>]START CHRONYD.
>
>Yes, the fact that if you change your rtc chrony has no way of
>compensating for it, because it does not and cannot know that it has
>happened, so chrony does not solve the problem of daylight savings time
>if you have your computer rtc on local time. Agreed. What it does solve
>is the problem of having your rtc on local time.
>
>
>

If you have access to a NTP server you just run ntpdate early in the
boot process and you can then ignore the RTC clock completely. If you
don't have access to a NTP server you would not be running chrony either,
would you.

Villy

Relevant Pages

  • Re: Setting The System Clock [Linux]
    ... but chrony also corrects for your rtc errors. ... it is on local time, and display that time. ... ] `chronyd' assumes by default that the real time clock keeps ...
    (comp.os.linux.misc)
  • Re: Chrony on an Isolated Machine
    ... >> enabled it messes with rtc (basically disables it and chrony handles it ... What is HPET? ... However it really is not compatible with rtc. ... Thereafter system time is already correct and you should not ...
    (comp.os.linux.networking)
  • Re: incorrect times displayed
    ... I'm running Chrony here. ... Did you file a bug report? ... If I told chrony to control the rtc it ...
    (Debian-User)
  • Re: Chrony on an Isolated Machine
    ... ls -l rtc on both machines gives the same response ... Same on test machine. ... chrony is going to HAVE to be rewritten. ... Thereafter system time is already correct and you should ...
    (comp.os.linux.networking)
  • Re: What time is it? Issues with Local time, system time, DST
    ... be for local time, not UTC. ... RTC, so that when processor is asleep or off, onboard batteries ... So is the standard way to handle this to store time zone and DST state ... The time zone which is set for the device is stored in the registry by ...
    (microsoft.public.windowsce.platbuilder)