Evolution of the ATLAS Nightly Build System

For over 10 years of development the ATLAS Nightly Build System has evolved into a factory for automatic release production and grid distribution. The numerous branches of ATLAS releases provide vast opportunities for testing new packages, verification of patches to existing software, and migration to new platforms and compilers for ATLAS code that currently contains ~2200 packages with 4 million C++ and 1.4 million python scripting lines written by ~1000 developers. The nightly releases lead up to stable releases used for data processing and analysis worldwide. The ATLAS Nightly System is managed by the NICOS control tool on the ATLAS Build Farm. The ATN testing framework runs unit and integration tests for the nightly releases.