What is the default value for an udev rule related to device attribute changes?

The default action for an udev rule related to device attribute changes is to use the "add" action. This action is triggered when a device is added to the system and is meant to apply any specified rules or configurations associated with that device.

When udev processes an event corresponding to a device being connected, it evaluates the rules defined for that device. The "add" action allows the system to apply attributes, create device nodes, or run specific scripts and commands as part of device management. This ensures that when the device is recognized by the system, all desired attributes or actions specified in the udev rules are executed.

Understanding this action can be crucial for system administrators who configure device handling and need to respond to hardware changes dynamically within a Linux environment.