On 04/24/2013 12:01 PM, Bill Davidsen issued this missive:
Rick Stevens wrote:
On 04/23/2013 03:31 PM, Bill Davidsen issued this missive:
I am getting some data on mountable media, and the device which writes
the files runs in EST or whatever you want to call five hours west of
Greenwich with no daylight time. The problem is that on a FAT or
ISO-9660 filesystem, the date and time seem to all jump an hour during
daylight time. Is there a better way to get the time correct than to run
a separate system which doesn't use daylight savings?
I have tried exporting TZ=EST5 (or EST or UTC-5 or GMT-5) to the mount
command or the rsync command, that doesn't seem to help anything, I need
the incoming data treated as EST, while the machine is at EST5EDT.
Hopefully you have the "System clock uses UTC" set on your Linux system.
If so, then all internal timestamps use UTC. They are converted to local
time when displayed (via "ls" or whatever). Winblows boxes don't do
that...they use the local time as the timestamp mechanism, so there's
the rub (also the cause of many issues with dual-booting machines).
You can either set your Linux box to not use UTC as the system clock
(I don't like that) or just deal with the idiocy that is Windows. It's
your system and your call.
No Windows involved, just some data logging machinery which writes info
in VFAT or ISO-9660 formats depending on the nmodel.
That equipment probably still uses localtime (if it's DOS- or
CP/M-based). I just used Windows as an example as it is known to cause
this sort of problem.
But no daylight
changes on the big boxes, I just have to make the data be local time for
reports and comparison. The simple way is to run EST on the system which
reads to data into Linux. Linux is a tad too smart here.
Actually, using UTC as the core gives all systems a consistent view of
the current time, regardless of where they're located. The Unix epoch
time is 00:00:00 1 January 1970 UTC after all.
Converting this UTC time to local when displayed is a convenience for
us humans.
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- Rick Stevens, Systems Engineer, AllDigital ricks@xxxxxxxxxxxxxx -
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- To understand recursion, you must first understand recursion. -
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