Thursday Aug 29, 2013

Timezone troubles when dual booting

I have a laptop that dual boots Solaris and Windows XP. When I switched between the two OSes I would have to reset the clock because the time would be eight hours out. This has been naggging at me for a while, so I dug into what was going on.

It seems that Windows assumes that the Real-Time Clock (RTC) in the bios is using local time. So it will read the clock and display whatever time is shown there.

Solaris on the other hand assumes that the clock is in Universal Time Format (UTC), so you have to apply a time zone transformation in order to get to the local time.

Obviously, if you adjust the clock to make one correct, then the other is wrong.

To me, it seems more natural to have the clock in a laptop work on UTC - because when you travel the local time changes. There is a registry setting in Windows that, when set to 1, tells the machine to use UTC:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal

However, it has some problems and is potentially not robust over sleep. So we have to work the other way, and get Solaris to use local time. Fortunately, this is a relatively simple change running the following as root (pick the appropriate timezone for your location):

rtc -z US/Pacific

Saturday Jul 19, 2008

Unable to explore CD on Windows XP

So we were given a number of photos on a CD and I wanted to copy them onto the XP machine. The problem I hit was that the CD appeared in Explorer, but I could not open it and browse the contents. I could open it as Administrator, but not as a normal user. Of course there was no error message, and no way of identifying where the problem was.

Anyway after a bit of googling and rejecting of the more time intensive "solutions" (reinstall XP, or try some utility from an unknown source), I found this conversation which described a similar problem and suggested the solution of "Enabling CD recording on this drive" from the properties menu of the DVD drive. Fortunately this seems to have worked, it also seems to still work even though I've switched the capability off again.

Right... now I can copy over those pictures....

About

Darryl Gove is a senior engineer in the Solaris Studio team, working on optimising applications and benchmarks for current and future processors. He is also the author of the books:
Multicore Application Programming
Solaris Application Programming
The Developer's Edge

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