DEVFS

DEVFS is a special-purpose file system present on many UNIX-like operating systems, including FreeBSD and Linux (though not all Linux systems enable it).

On all Unix systems, many I/O devices (such as disks, printers, virtual terminals and so forth) are treated by the operating system as special files. However, maintaining these special files on a conventional file system can become quite complex: this is particularly the case where arbitrary devices can be hot-swapped (installed or removed whilst the system is operational) such as USB devices. DEVFS simplifies this problem by automatically overseeing the creation, deletion, and permission management of these files.