Hot plugging refers to the system for managing devices that can be automatically replaced or installed without shutting down the attached computer. Hot plugging is also known as hot swapping. It is implemented when you have the need to add or remove a peripheral device, to carry out the reconfiguration of a device or working system is required, to replace the defective component or device or to realize the synchronization of data. Generally speaking, the most popular use for hot plugging system is handling the USB and firewire device, though it is also widely applied into the use of PCI, tape drives, SCSI devices, the device within which the firmware is loaded, input devices and so on. The hot plugging system consists of a kernel part and a userland part. On the other hand, it allows the equipment to get an easy access to it and brings great conveniences for it enables the system to be uninterrupted.
Moreover, anything happening as an action or event can be called as hotplug. Generally speaking, there are two main types of hot plugging, namely, add and remove a device, which are also referred to as register and unregister a device according to the subsystem files you are looking at.
As the above-mentioned information stated, the device is swapped while the computer is running or hot, and this is how hot plugging or hot swapping gets it name. Meanwhile, such device is also known as “hotpluggable”. On the other hand, the device cannot be added or removed under such circumstances is referred to as cold plugging.
There is some kind of standard in terms of judging whether the device is hotpluggable or not. First of all, it must be able to connect to a running computer and operate nearly instantaneously. In addition, a mechanism supporting hot plugging has to be able to figure out the replaced or removed modules or devices. Last but not least, the mechanical and electrical connection must add or remove the device safely without causing any harm to the device or user.