Config is a tool used in building 4.3BSD system images (the UNIX kernel). It takes a file describing a system's tunable parameters and hardware support, and generates a collection of files which are then used to build a copy of UNIX appropriate to that configuration. Config simplifies system maintenance by isolating system dependencies in a single, easy to understand, file.

This document describes the content and format of system configuration files and the rules which must be followed when creating these files. Example configuration files are constructed and discussed.

Later sections suggest guidelines to be used in modifying system source and explain some of the inner workings of the autoconfiguration process. Appendix D summarizes the rules used in calculating the most important system data structures and indicates some inherent system data structure size limitations (and how to go about modifying them).