Every device and every interface has an associated hotplug event, which is processed by the relevant hotplug agent. Hotplug events are triggered either by the kernel when a link is established to a device or by coldplug, which checks the main buses at regular intervals and creates an event for all devices that have not been initialized. Further information on coldplug is provided in Section 14.7. “Coldplug”. The kernel also initiates a hotplug event as soon as a driver registers an interface.
A hotplug event is a call to a hotplug user-mode tool, such as /sbin/hotplug, which is specified in file /proc/sys/kernel/hotplug. /sbin/hotplug searches for a hotplug agent that matches the type of event. If there is no suitable agent but there is a dev file in the device path, the agent generic_udev.agent is called.
To ensure that events of a particular kind are ignored, edit file /etc/sysconfig/hotplug and set the desired event to HOTPLUG_SKIP_EVENTS.