The /proc file system really shows the power of the Linux Virtual File System. It does not really exist (yet another of Linux's conjuring tricks), neither the /proc directory nor its subdirectories and its files actually exist. So how can you cat /proc/devices? The /proc file system, like a real file system, registers itself with the Virtual file system. However, when the VFS makes calls to it requesting inodes as its files and directories are opened, the /proc file system creates those files and directories from information within the kernel. For example, the kernel's /proc/devices file is generated from the kernel's data structures describing its devices.
The /proc file system presents a user readable window into the kernel's
inner workings.
Several Linux subsystems, such as Linux kernel modules described in
chapter 
.