Device Management Definitions
Hotplugging is often taken to mean the opposite of coldplugging—in other words, the ability of a computer system to add or remove hardware without powering the system down. Examples of devices that are coldpluggable include PCI (some PCI chipsets have hotplug support, but these are very expensive and almost exclusively used in server systems), ISA devices, and PATA devices.
In most computer systems, CPUs and memory are coldpluggable, but it is common for high-end servers and mainframes to feature hotplug capability of these components.
sysfs is a RAM-based filesystem initially based on ramfs. It provides a means to export kernel data structures, their attributes, and the linkages between them to the user space. sysfs contains several directory hierarchies showing the available hardware devices and attributes of the modules/drivers. It can be accessed by running:
# mount -t sysfs sysfs /sys
The udev process uses sysfs to get the information it needs about the hardware and creates dynamic device files as kernel modules are loaded. The directory /etc/udev.d holds all the rules to be applied when adding or removing a device.
D-Bus is an application that uses sysfs to implement a message bus daemon. It is used for broadcasting system events such as “new hardware device added” or “printer queue changed” and is normally launched by an init script called messagebus.
The hald process is the daemon that maintains a database of the devices connected to the system in ...