FUSE (Filesystem in user space) - http://fuse.sf.net - allows to write filesystem code in userspace. This package provides bindings for libfuse, userspace library implementing the fuse protocol. fuse-test.lisp is a minimal usage example. It mounts an FS at /tmp/test. It contains many-files (a directory with many symlinks named by consequtive numbers), same-name (no entries in ls; you can cat a file -it will contain its name) and symlinks (no entries in ls - every name exists as a symlink to the same name under /).