For newly Plugged-in device , given below steps take place
1. Kernel detect the Plug-in device and export device status to sysfs. You can view exported state via mounted /sys virtual filesystem.
2. Kernel then notify udev about this event via netlink socket.
3. udev process the user-configurable rules (present in /etc/udev/rules.d) and creates device file in /dev.
4. After creating device node , udev notify hald about the event via the socket.
5. HAL probes the device for information.
6. The device object structure populates with the probed information.
7. HAL broadcast Plug-in event.
8. A user-space application then process the information.