Request for Comments: updating RPMs using binary deltas.

[M A Young]

Alan Cox wrote:

>Problem 1:  Gzip files don't rsync well. bzip2 files I'm not sure of the
>situation. Rusty did work with rsyncable dpkg files and along with Tridge
>hacked up a gzip library that generated slightly larger rsyncable files.
>That change was tested ages ago in rpm and broke stuff so went back out.
>I don't know if anyone ever sat down and debugged it in full

rsync and indeed any other similar program won't work well with compressed
data, and so the rpms need to be uncompressed first.

>Problem 3:  Server resources. The rsync computation clobbers the server
>compared to the overhead of just spewing bits. Given people are running
>3000 vsftp sessions in parallel off big servers that is a concern.

There is a feature missing from rsync that would be useful here. It would
be nice if rsync could record a difference between two files, which could
be used later to transform the first file to the second on another
machine. This would be quite a good way to transform an uncompressed copy
of distributed rpm into a later version. In particular the heavy
calculations used to generate rsync differences only need to be done once
on the server. I would have thought that adding this feature to rsync
should be easy (assuming someone hasn't already).

	Michael Young