Linux, in the tradition of UNIX-like operating systems, implements file system permissions using a rather coarse scheme. While this is sufficient for a surprisingly large set of applications, it is too inflexible for many other scenarios. For that reason, all the major commercial UNIX operating systems have extended this simple scheme in one way or the other. This is an effort to implement POSIX-like Access Control Lists for Linux. Access Control Lists are built on top of Extended Attributes, which can also be used to associate other pieces of information with files such as Filesystem Capabilities, or user data like mime type and search keywords.
fam++ is a C++ wrapper for fam, which uses imon or DNotify (Linux 2.4.x) to inform it when inodes change (the net effect being that applications can register interest in a file, and have events send to the application when the file changes). Fam++ also integrates with gdk and Loki to make creation of C++ GTK+/GNOME apps simpler.
fistgen is the FiST language code generator, used to create stackable file systems out of templates and a high-level language. This package comes with stackable file system templates for Linux, Solaris, and FreeBSD. It also contains several sample file systems built using the FiST language: an encryption file system, a compression file system, and more - all of which are written as portable stackable file systems.
FSlint is a toolkit to find various forms of lint on a filesystem. At the moment it reports duplicate files, bad symbolic links, troublesome file names, empty directories, non stripped executables, temporary files, duplicate/conflicting (binary) names, and unused ext2 directory blocks.
GNU Parted is a package for creating, destroying, resizing, checking, and copying partitions and the file systems on them. This is useful for creating space for new operating systems, reorganizing disk usage, copying data between hard disks, and disk imaging. It contains a library, libparted, and a command-line frontend, parted, which also serves as a sample implementation and script backend.
hfsutils is a comprehensive software package being developed to permit manipulation of HFS volumes from UNIX and other systems. HFS is the ``Hierarchical File System,'' the native volume format used on modern Macintosh computers. The software reads and writes HFS (but not HFS+) volumes with several command-line programs and optionally an X interface. The software can also be used as a C library.