FOSDEM

In the future, a one-line security update or dist-upgrade should mean a smaller download. Existing technologies such as diff, bsdiff, zsync and xdelta reduce the amount of data transferred by detecting similarity between two revisions of a binary or source package.

Current methods are restricted to updates between specific versions (pdiff), require heavy server support (rsync), or are adversely affected by the gzip and bzip2 compression used within Debian packages.

A generic solution, 'apt-sync', allows updating the contents of a package between any currently installed version, to the latest, in a bandwidth efficient way. Based on ideas from 'zsync', the existing compression and 'dumb' HTTP mirror network are utilised in a backwards compatible manner; with all computation performed by the client.

Early code produced from Google's SoC is being low-key tested within Ubuntu and is available in the 'apt-sync' package, supported by meta-data on people.ubuntu.com/~mvo/apt-sync.