Re: Offline sync rool a la rsync ?

[Goswin Brederlow <goswin.brederlow@student.uni-tuebingen.de>]

>>>>> " " == Petr Cech <cech@atrey.karlin.mff.cuni.cz> writes:

     > On Wed, Jan 17, 2001 at 06:45:29PM +0100 , Gregor Hoffleit
     > wrote:
    >> I'm looking for a tool like rsync that's able to work in
    >> offline mode.  Imagine a machine has no internet connection,
    >> but keeps a repository of files. At another machine, there's a
    >> second instance of that repository. Now I'd like to be able to
    >> use e.g. a zip disk to carry the changes from one site to the
    >> other and back.

     > xdelta. dunno if it works on multiple files though. but some
     > shellscript could probably fix that Petr Cech -- Debian
     > GNU/Linux maintainer - www.debian.{org,cz}
     > cech@atrey.karlin.mff.cuni.cz

You could make rsync do this. But rsync needs two roundtrips AFAIK:

-- day 1 --
1. request a listing of all files to be synced
2. get listing

-- day 2 --
3. create checksums, delete old files, make new directories
4. send checksums
5. get differing blocks

So you only need to implement RFC 1149: "A Standard for the
Transmission of IP Datagrams on Avian Carriers" for linux and play
pigeon.

:))

You could probably use most of the code from rsync to do what you
want. You know the directories you want to sync, so no need to bother
with that. You also roughly know the filelisting, so just assume the
listing will be equal to what you have at home and generate checksums
for every file in the tree. Take that to the connected maschine, run
the rsync algorithm over it to generate the real filelisting and the
needed block updates. Take those home and apply the second part of the
rsync process.

Noone has done this yet, but it looks doable and efficient.

MfG
        Goswin