Every device and every interface has an associated hotplug
event, which is processed by udev and the
responsible hotplug agent. Hotplug events are triggered by the kernel when
a link to a device is established or removed or when a driver registers or
deletes an interface.
Since SUSE LINUX 9.3, udevd receives and
dispenses hotplug events. Either udevd listens directly
to netlink messages from the kernel or
must be specified in
udevd has done its job (see Chapter 19, Dynamic Device Nodes with udev),
it searches for a hotplug agent in
that matches the type of event.