libguestfs is a set of tools for accessing and modifying virtual machine (VM) disk images. You can use this for viewing and editing files inside guests, scripting changes to VMs, monitoring disk used/free statistics, P2V, V2V, performing partial backups, cloning VMs, and much more. libguestfs can access nearly any type of filesystem including: all known types of Linux filesystem (ext2/3/4, XFS, btrfs, etc.), any Windows filesystem (VFAT and NTFS), any Mac OS X and BSD filesystems, LVM2 volumes, MBR and GPT disk partitions, raw disks, qcow2, CD and DVD ISO images, SD cards, and dozens more. libguestfs doesn't need root permissions.
MinorFS combines a small set of cooperating userspace filesystems for Linux that provide private storage to pseudo persistent processes. This allows programs that are run by a user to keep some data safe from all potential malware that runs with all this users' privileges. It further implements simple password capabilities as a way to explicitly share access with other processes or users.
Ceph is a distributed network file system designed to provide excellent performance, reliability, and scalability (from terabytes to exabytes). Data is stored in the form of "objects" (variable length, named chunks of data) in a distributed and fault tolerant cluster of OSDs (object storage devices--servers running the Ceph OSD daemon). Metadata (the file system namespace) is managed by an independent cluster of metadata servers (MDSs), which dynamically repartitions the directory hierarchy in response to the current workload.
JIIC is a streaming-based Java implementation of ISO 9660 for creating CD-ROM filesystem images ("ISO images") with the extensions El Torito, Joliet, and Rock Ridge. It is based on the SABRE streaming API, and provides an Ant task for easy integration into Java-based build processes.
MT-write is a binary patch for multi-threaded writing. It comes in the form of a shared object that can be preloaded to programs like tar to make their write operations multi-threaded. Multi-threaded writing can improve performance on RAM based filesystems and highly scalable filesystems with multiple spindles.
rootpretender is a system that enables special file operations such as the creation of block special and character special device nodes and unlimited chown()ing of files for non-root users of Unix systems. It does this by faking special file operations. For example, chown() is not executed, and mknod() creates regular files instead of device nodes. These operations are remembered, so next time a process under rootpretender's control examines an affected file with stat() or a similar system call, the fake information is returned. It uses LD_PRELOAD and includes patches for rsync 2.6.6 and rsync 2.6.9 for use on systems without LD_PRELOAD support. These make it possible to copy file ownership and device nodes even if root access is not available on the target.