Abstract: The present invention provides a method and apparatus for restricting a process or process hierarchy to a subset of a computer host's file system(s) in an environment where all file systems are simultaneously available to an application. A caller is provided with the ability to arrange for the restriction of a process hierarchy (consisting of a process and all the processes it may subsequently create) to a set of file system sub-hierarchies. When a process executes within a restriction domain in which a sub-hierarchy has been specified for each of the available file systems, an embodiment of the invention will modify the usual operation of the host computer's operating system interface such that any file system access attempts by the affected process are constrained to occur logically within the restriction domain.