On or about 2005-03-02 06:14, Alan McDonald whipped out a trusty #2 pencil and scribbled:
I synchronise some files across an ftp connection. The files comes from aI'm presuming that this involves moving files from a Windows machine to Linux, or vv. Both Windows and Linux use UTC for timestamps. The difference is, in Windows you set the hardware clock to your local time, tell it which timezone you're in, and it converts to UTC when stamping file times. Likewise, it converts timestamps back to local time for DISPLAY purposes when you list the directory.
computer with the current date/time set, and my PC is also set with correct
time (both clock and hwclock return the correct time). But the files which
are writtin into the ftp directory are 13 hours ascew.. How can I correct
this? Where is the magic setting for making files writen to disk obey the
curret clock?
thanks
Alan
Linux/Unix do it the other way. The hardware clock is usually set to UTC, you tell it what time zone you're in, and the DISPLAY of times will be in local, but timestamps on files will be in UTC.
As a convenience to those who have one machine with a dual-boot of Windows/Linux, most distros allow you to declare that the hardware clock is actually not UTC, but local. Then when Linux boots, it reads the hardware clock, applies the TZ correction, then sets the system clock to UTC. If you tell Linux the hardware clock is UTC, then it doesn't apply the correction on boot, just sets the system clock to the hardware clock, and goes on as usual.
Windows of course, has no facility to be told that the hardware clock is on UTC, and to correct for local time zone on booting. So for Windows you must set local time on the hardware clock.
Another problem is that you can have your Windows time zone set incorrectly, and someone has set the hardware clock to compensate. So if I in the US Central TZ set my Windows system to the Greenwich time zone, then fiddle with the clock setting so that the time "looks correct", then Windows will think it does not need to apply any correction to get UTC, but all it's timestamps will then be off by 6 hours. (A file created at 8:00 am local time would actually be stamped as 0800 UTC, when it really should be stamped as 0200 UTC.)
Oooops! That should be 1400 UTC, not 0200 UTC. Sorry if the example caused even more confusion...
Similar things of course can happen in Linux, in the opposite direction, if you don't have your TZ data set correctly and just force the clock to look like correct local time.
-- Fritz Whittington Man is by nature a political animal. (Aristotle, Politics)
