FUSE 3

FUSE3 is the 3.x version of Filesystem in Userspace, a framework that allows userspace programs to implement filesystem interfaces visible to the Linux kernel. This provides a secure method for non-privileged users to create and mount custom filesystems without requiring kernel modules. The package includes tools like fusermount, fusermount3, mount.fuse, and mount.fuse3 for mounting and unmounting operations.

Key components include the transitional 'fuse' package, which depends on fuse3 and can be safely removed after installation. The libfuse3-4 library supports runtime functionality, while libfuse3-dev provides development files for building custom FUSE implementations. fusermount and fusermount3 handle mounting and unmounting FUSE filesystems, with options for quiet operation, lazy unmounts, and custom mount options.

Use cases include creating virtual filesystems for encryption, network filesystems, or in-memory storage without kernel modifications. It is particularly useful in cybersecurity for mounting forensic images, encrypted volumes, or custom data structures securely from userspace.

FUSE3 operates by providing a kernel module that communicates with userspace filesystem implementations via a FUSE protocol over /dev/fuse. Userspace programs handle filesystem operations (read, write, mkdir, etc.) through the libfuse3 library, which translates kernel requests into function calls. Tools like fusermount3 use the mount protocol to attach the virtual filesystem to a mountpoint, supporting options for security and performance. The secure design restricts operations to the calling user, preventing privilege escalation.