Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.debian.user > #173686

Re: Time quandry when dual boot with WinXP Pro

Show all headers | View raw

On Fri, Oct 21, 2016 at 08:09:38AM -0500, Richard Owlett wrote:
>I'm creating a preseed.cfg file for installing Debian 8.6 in a 
>dual-boot enviroment with some version of MS Windows. There are two 
>distinct use cases:
>   1. Two of my machines with WinXP Pro SP3
>   2. A remote (~1000 miles]friend with several machines - some with 
>WinXP, others with
>      Windows 10 or later.
>
>I have discovered on my WinXP machine that:
>   1. WinXP _displays_ the correct time.
>      "Date and Time Properties" - Time Zone set to
>          (GMT-06:00)Central Time(US&Canada)
>          Automatically adjust clock for daylight saving changes
>   2. Debian 8.6 w MATE run from LIVE DVD _displays_ the correct time
>   3. Debian 8.6 w MATE installed from DVD 1 of 13 with aid of custom 
>preseed.cfg
>      _displays_ a time 5 hours earlier.
>      The _display_ is independent of whether
>           d-i clock-setup/utc boolean true
>                       *OR*
>           d-i clock-setup/utc boolean false
>      is used in the preseed.cfg file.
>
>I'm confused.

If you're not using NTP to provide your time, then, at boot, the 
operating system will query the "hardware clock" to see what time it is.  
As the hardware clock can drift, operating systems will also set the 
hardware clock to match the "system clock" at shutdown time (the system 
clock is the time that the operating system is using).

The problem comes that there is no way for the hardware clock (HWClock) 
to report what timezone it was set to. There are basically two options 
here:

 1. The HWClock is set to "Local Time". In this case, the operating 
 system sees "12:23" as being "12:23 GMT" or "12:23 CST" or whatever and 
 attempts no translation of the clock.

 2. The HWClock is set to "Universal Time" (which is a non-geographical 
 datum time zone, with no daylight changes). In this case, the operating 
 system sees "12:23" as ONLY being "12:23 UTC" and translates that into 
 the local time zone by adding or subtracting hours appropriately.

If you only have one operating system on your machine, either of these 
methods is fine. If you have TWO (or more) operating systems, though, 
then they SHOULD agree on what the time in the HWClock represents. If 
Windows thinks it's local time, but Debian thinks it's UTC, then you'll 
see five-hour shifts each time you boot.

You've already found the setting in Debian, I see, so you probably want 
to check it tallies with what Windows is using. For that, look at the 
Registry Key 
HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal.  
If this is 1, then the HWClock is using UTC; if it is 0, then the 
HWClock is set to local time.

Hopefully that helps.

>
>
>
>

-- 
For more information, please reread.

Back to linux.debian.user | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 15:20 +0200
  Re: Time quandry when dual boot with WinXP Pro Darac Marjal <mailinglist@darac.org.uk> - 2016-10-21 15:30 +0200
    Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 16:50 +0200
    Re: Time quandry when dual boot with WinXP Pro David Wright <deblis@lionunicorn.co.uk> - 2016-10-21 17:10 +0200
      Re: Time quandry when dual boot with WinXP Pro Joe <joe@jretrading.com> - 2016-10-21 19:50 +0200
        Re: Time quandry when dual boot with WinXP Pro David Wright <deblis@lionunicorn.co.uk> - 2016-10-22 17:10 +0200
          Re: Time quandry when dual boot with WinXP Pro Joe <joe@jretrading.com> - 2016-10-22 17:10 +0200
          Re: Time quandry when dual boot with WinXP Pro Joe <joe@jretrading.com> - 2016-10-22 17:50 +0200
            Re: Time quandry when dual boot with WinXP Pro David Wright <deblis@lionunicorn.co.uk> - 2016-10-23 04:50 +0200
  Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 15:40 +0200
    Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 16:30 +0200
      Re: Time quandry when dual boot with WinXP Pro Doug <dmcgarrett@optonline.net> - 2016-10-21 18:50 +0200
        Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 20:20 +0200
          Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 21:20 +0200
      Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 21:20 +0200
        Re: Time quandry when dual boot with WinXP Pro tomas@tuxteam.de - 2016-10-21 21:30 +0200
          Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-21 22:20 +0200
            Re: Time quandry when dual boot with WinXP Pro <tomas@tuxteam.de> - 2016-10-21 22:40 +0200
  Re: Time quandry when dual boot with WinXP Pro Stefan Monnier <monnier@iro.umontreal.ca> - 2016-10-22 22:10 +0200
    Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-22 22:20 +0200
      Re: Time quandry when dual boot with WinXP Pro Stefan Monnier <monnier@iro.umontreal.ca> - 2016-10-22 22:20 +0200
        [REPOST] Re: Time quandry when dual boot with WinXP Pro Richard Owlett <rowlett@cloud85.net> - 2016-10-25 14:20 +0200
        Side effects of specifying use of NTP on installation???? - was [Re:  Time quandry when dual boot with WinXP Pro] Richard Owlett <rowlett@cloud85.net> - 2016-10-25 14:20 +0200
  Re: Time quandry when dual boot with WinXP Pro Lisi Reisz <lisi.reisz@gmail.com> - 2016-10-29 16:50 +0200
    Re: Time quandry when dual boot with WinXP Pro Felix Miata <mrmazda@earthlink.net> - 2016-10-29 17:30 +0200
      Re: Time quandry when dual boot with WinXP Pro Lisi Reisz <lisi.reisz@gmail.com> - 2016-10-29 18:20 +0200

csiph-web