Filesystem in Userspace (FUSE) is a Unix-like operating system software interface that lets non-privileged users create their own file systems without editing kernel code.

To define a new filesystem, you need to write a handler program. This program maps how filesystem is mounted and how it responds to read, write and stat requests.

FUSE is mainly used for writing virtual filesystems. Traditional filesystems work with mass storage devices while virtual filesystems don't store the data themselves but only act as a view to the data.

Examples:

• GmailFS, stores data as emails in Gmail.
• KBFS, encrypts and stores data on Keybase.io.
• s3fs, stores data in AWS S3 buckets.
• SSHFS, remote filesystem mount through SSH.
• WikpediaFS, view and edit Wikipedia articles as they were files.

Sources

• Wikipedia - FUSE