Udev (userspace /dev) is a Linux sub-system for dynamic device detection and management, since kernel version 2.6. It???s a replacement of devfs and hotplug. It dynamically creates or removes device nodes (an interface to a device driver that appears in a file system as if it were an ordinary file, stored under the /dev directory) at boot time or if you add a device to or remove a device from the system. It then propagates information about a device or changes to its state to user space.