Murray Stokely has released the FreeBSD Release Engineering paper detailing the different phases of the release engineering process leading up to the actual system build as well as the actual build process and very important discussion on the future directions of development:
This paper describes the approach used by the FreeBSD release engineering team to make production quality releases of the FreeBSD Operating System. It details the methodology used for the official FreeBSD releases and describes the tools available for those interested in producing customized FreeBSD releases for corporate rollouts or commercial productization.
The development of FreeBSD is a very open process. FreeBSD is comprised of contributions from thousands of people around the world. The FreeBSD Project provides anonymous CVS access to the general public so that others can have access to log messages, diffs (patches) between development branches, and other productivity enhancements that formal source code management provides. This has been a huge help in attracting more talented developers to FreeBSD. However, I think everyone would agree that chaos would soon manifest if write access was opened up to everyone on the Internet. Therefore only a “select” group of nearly 300 people are given write access to the CVS repository. These committers are responsible for the bulk of FreeBSD development. An elected core-team of very senior developers provides some level of direction over the project.
The rapid pace of FreeBSD development leaves little time for polishing the development system into a production quality release. To solve this dilemma, development continues on two parallel tracks. The main development branch is the HEAD or trunk of our CVS tree, known as “FreeBSD-CURRENT” or “-CURRENT” for short.
A more stable branch is maintained, known as “FreeBSD-STABLE” or “-STABLE” for short. Both branches live in a master CVS repository in California and are replicated via CVSup to mirrors all over the world. FreeBSD-CURRENT is the “bleeding-edge” of FreeBSD development where all new changes first enter the system. FreeBSD-STABLE is the development branch from which major releases are made. Changes go into this branch at a different pace, and with the general assumption that they have first gone into FreeBSD-CURRENT and have been thoroughly tested by our user community.
In the interim period between releases, monthly snapshots are built automatically by the FreeBSD Project build machines and made available for download fromftp://ftp.freebsd.org/pub/FreeBSD/snapshots/. The widespread availability of binary release snapshots, and the tendency of our user community to keep up with -STABLE development with CVSup and “make world” helps to keep FreeBSD-STABLE in a very reliable condition even before the quality assurance activities ramp up pending a major release.