This page is dedicated to the debdelta package and service.
debdelta is an application suite designed to compute changes between Debian packages. These changes (that we will call 'deltas') are similar to the output of the "diff" program in that they may be used to store and transmit only the changes between Debian packages. This suite contains 'debdelta-upgrade', that downloads deltas and use them to create all Debian packages needed for an 'apt-get upgrade'.
Debdelta is available as a Debian package. Debdelta is written and mantained by this guy. The source is made available using git, please visit to obtain a copy. The source code is copyright A Mennucci 2006-2021 and licensed GPL-v2.
debdelta-upgrade service
There is a server that generates deltas for upgrades of packages in the Debian repository archives. The server generates deltas by looking at the current state of the archives and at the state before, then it generates all deltas needed to upgrade. It also deletes all deltas that would upgrade to a package version that is not present in the archive any more, and all deltas older than 50 days. The server provides logs and statistics here. The script that manages all this is debdeltas_server (In the past another script was used: /usr/share/debdelta/debmirror-marshal-deltas, distributed in debdelta >= 0.41).

More info specific to 'debdelta-upgrade' are in the documentation.
To download deltas, debdelta-upgrade looks into /etc/debdelta/sources.conf; this is what is available at each stanza (as of Mar 2011).
debdelta-upgrade service news
The server that creates the deltas keeps logs and statistics.
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