Win32 and Backing up open files

Jason M. Felice jfelice at
Tue Mar 2 18:07:12 GMT 2004

I now fully and completely remember why I hate Windows.

I have struggled with the backup semantics options in order to get rsync
able to back up open files, and I got something that appeared like it
should work, but it didn't work.  So I finally broke down and wrote a
holdopen.exe and a tryopen.exe to test my theory, and no matter what
privleges were enabled (backup and restore were enabled), a program
under Windows can _NOT_ open a file which has been opened if the
original opener has not specified read sharing.  No matter what.

A much more careful reading of the docs indicates that backup semantics
only allow you to bypass _security_ restrictions, not sharing
restrictions (as well as allowing access to security information about
the file).

I can't believe it.  This means that most backups under Windows are
completely useless unless programs avoid opening a file without

One backup program claims to be able to back up unshared, open files.  They
say that they do it with a custom kernel driver which allows them direct
access to the file.  This, of course, is beyond the scope of my charter
for modifying rsync.

 Jason M. Felice
 Cronosys, LLC <>
 216.221.4600 x302

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