important caveat with Rsync on NT and dayligt savings time

[bart.coninckx at sita.be]

If I understand the manpages correctly, if you use -t, the criterium for
syncing files is the difference in timestamp, not in size.
There are plenty of situations where the size of a file stays identical,
while it's contents has changed.
If you omit -t, all files are synced.


Rgds,


Bart Coninckx
Network Administrator
CNE, ASE
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                    Lachlan Cranswick                                                                                               
                    <l.m.d.cranswick@        To:     rsync at samba.org                                                                
                    dl.ac.uk>                cc:                                                                                    
                    Sent by:                 Subject:     Re: important caveat with Rsync on NT and dayligt savings time            
                    rsync-admin at lists                                                                                               
                    .samba.org                                                                                                      
                                                                                                                                    
                                                                                                                                    
                    10/29/2002 21:35                                                                                                
                                                                                                                                    
                                                                                                                                    




I think this "day light savings" time stamp issue also affects
Win98 as well - at least on a Win98 PC I use.
Rsync insists on updating all the files fully.
Shouldn't it just be resetting the times on the files
if the files are the same size - or am I missing
something here?

Lachlan.


>Your description is as confusing as the KB article (at least
>to me).  Part of the problem with the KB article is that it
>focuses on localtime displays rather than internals.
>
>.From what i can tell FAT stores timestamps in localtime.
>NTFS uses a GMT based timestamp.
>
>I can see one of two places where we get bit.  As a matter
>of curiosity i'd like to know which.
>
>1. When the FAT timestamps are converted to GMT it is done
>   based on the current TZ offset rather than the TZ offset
>   in effect when the timestamp was made.
>
>2. The NT equivalent of stat(2) is converting the NTFS
>   timestamps to localtime and then the cygwin libs convert
>   it back to GMT.
>
>It would appear that the problem could be avoided either by
>using NTFS or FAT filesystems.  Yes?   It certainly sounds
>filesystem dependant.
>
>I'd guess that the correct place to fix this is in the
>cygwin libs.  They could be tweaked to recognize the TZ
>calculation error of the NT libs.  There might need to be a
>test for filesystem type (if possible) or a switch to
>determine behavior otherwise what fixes some will break
>others.

-----------------------
Lachlan M. D. Cranswick

Collaborative Computational Project No 14 (CCP14)
    for Single Crystal and Powder Diffraction
  Birkbeck University of London and Daresbury Synchrotron Laboratory
Postal Address: CCP14 - School of Crystallography,
                Birkbeck College,
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