via Amit (see Blogroll)

Mac OS X Filesystems
Local Filesystems
(…)
Network Filesystems
(…)
Other/Pseudo Filesystems

fdesc

“The fdesc filesystem is typically mounted on /dev/fd. It’s functionality is similar to /proc//fd (or simply /proc/self/fd) on Linux, that is, it provides a list of all active file descriptors for the currently running process. Note that a typical Linux system has /dev/fd symbolically linked to /proc/self/fd.

/etc/rc mounts the fdesc filesystem during system startup (…)

The “/dev/fd*” files are special devices. These aren’t really taking up that much space on your system. They allow a process to access file descriptors by number; 0,1,2 are standard input, standard output, and standard error, and other open files start with 3.”

more info: ‘man mount_fdesc’ (8): mount the file-descriptor file system.