Introducing the Debian Continuous Integration project
Debian is a big system. At the time of writing, the unstable distribution has more than 20,000 source packages, building more then 40,000 binary packages on the amd64 architecture. The number of inter-dependencies between binary packages is mind-boggling: the entire dependency graph for the amd64 architecture contains a little more than 375,000 edges. If you want to expand the phrase "package A depends on package B", there are more than 375,000 pairs of packages A and B that can be used.