status of forked zlibs in rsync and zsync

Jonathan Underwood jonathan.underwood at
Thu Oct 1 16:42:00 UTC 2009

2009/10/1 Toshio Kuratomi <a.badger at>:
> On 10/01/2009 03:10 AM, Josephine Tannhäuser wrote:
>> 2009/9/14 Adam Williamson <awilliam at>
>>> Hi, everyone. We - the QA group - have recently been researching the
>>> feasibility of using zsync to reduce the size of live image downloads.
>>> This has hit a roadblock in the form of the problem where both rsync and
>>> zsync use forked zlibs rather than linking against the system copy.
>> Imho, allow zsync for fedora. If you can solve the zlib-problem of rsync,
>> the problem of zsync will be solved as well, cause the integrity of zsync in
>> fedora fails on rsync-compatibility, which needs a forked zlib.
> If you want it in, do the work.  I've outlined the possibilities several
> times:
> A) You're a coder and want to get your hands dirty with the rsync
> protocol.  Check out how librsync manages to use the system zlib and if
> possible to do this compatibly, apply it to zsync and rsync, possible as
> a build time option.  Push the changes upstream if possible.  If it's
> impossible to apply the librsync strategy, having a good explanation of
> what librsync is doing and why it can't work for rsync/zsync would be
> great for crossing this option off the list.

librsync is not wire compatible with rsync, and also hasn't kept up to
date with rsync protocol changes, so it may not be as straightforward
to lift ideas from librsync.

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