On Fri, 14 May 2010 21:01:15 -0400, Andrei Alexandrescu
<[email protected]> wrote:
Alex Makhotin wrote:
Andrei Alexandrescu wrote:
Date: Sat, 15 May 2010 04:46:08 +0300
That's a bit in the future. Any chance I could impose on you to change
your system time?
Every time I set the local time in Linux and then reload to Windows,
the Windows resets it in BIOS. So I set the Linux to use the UTC(as in
BIOS). To use the local time it requires me to set the clock back on 2
hours. I don't know why Windows resets BIOS clock...
Interesting. Can you instruct Windows to sync using the Internet? And
does Windows have the right time zone set?
Having dealt with a customer that insisted we always have the time set
properly, I can tell you that Windows uses the BIOS time as local time,
Linux *can* use the BIOS time as local time, but generally assumes it is
set to UTC (and adjusts it's working clock accordingly). During halt, it
saves the clock back to the BIOS in case anything has changed, and
generally uses UTC.
What is actually happening is that Windows *is* setting the time via the
internet, and then overwriting the BIOS time :)
AFAIK, the only way to fix this is to configure linux to treat the BIOS
time as local time. Do a man on hwclock, and read the notes at the
bottom. Since every Linux system has its own init scheme, it probably
varies from system to system. I'm pretty sure the kernel reads the HW
clock the first time, but once it reads it, it doesn't use it anymore.
halt usually sets the clock using hwclock. You can probably override the
kernel time by doing a hwclock read very early in the process, but that
means the kernel will think the time is off by whatever your timezone is
when it is starting up. This would probably best be done in the initrd
before the filesystem is mounted. There may be kernel parameters that
force this mode of reading the clock.
Funny anecdote (actually not really funny at the time): Our windows test
image for previously mentioned customer was set to use UTC time, but had
the checkbox set for "adjust for daylight savings" Well, there is no
daylight savings in UTC, but Windows still seemed to think during sysprep
that it was a good idea during certain dates of year to set the BIOS clock
ahead one hour. Since we booted twice during sysprep, all clocks went out
the door off by 2 hours. This did not go over well with said customer,
and we had to recall all the systems so they could be set properly (yes,
I'm not making this up, we had to boot these systems to our network, which
automatically set the time, and then shut them down).
-Steve
