Does the rsync/xdelta algorithm *need* to write a new file?

Arthur van Leeuwen arthurvl at
Thu May 23 07:22:02 EST 2002


lately I've been playing with the idea of doing in-place updates 
of systems using either rsync or xdelta. However, both rsync
and xdelta seem to be dead set on writing a new file first, and
then atomically exchanging it with the old file.

Now, as I want to apply a binary delta to a full filesystem, bigger 
than the available temporary space, this really makes rsync and
xdelta extremely tough to use (I could work around it, only updating 
blocks of half the size of the temporary space at a time, but that 
would defeat some of the savings gotten by calculating a delta over
the full filesystem: moves of data over block boundaries would incur 
extra overhead delta's)

Has anybody thought about doing in-place patching of files using

Another application where this would do wonders is people that rsync
complete ISO images: they would not need to reserve space for an
entire extra ISO on their systems.

Doei, Arthur. (Wondering if it is at all possible...)

+- Arthur van Leeuwen, Systems Consultant, arthurvl at -+
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