This book describes the Oracle Solaris Modular Debugger (MDB), which is a general purpose debugging tool for the Oracle Solaris operating system. The primary feature of MDB is its extensibility. This book describes how to use MDB to debug complex software systems, with a particular emphasis on the facilities available for debugging the Oracle Solaris kernel and associated device drivers and modules. The book also includes a complete reference for and discussion of the MDB language syntax, debugger features, and MDB module programming API.