Which of the following is used as a virtual or pseudo filesystem used to interface with the kernel and system as a whole but not with individual processes?

The correct choice refers to the /sys directory, which is indeed used as a virtual or pseudo filesystem that provides a means to interface with kernel data structures and system hardware. It is part of the sysfs filesystem and presents a view of kernel objects, allowing user-space applications to interact with devices and kernel subsystems in a structured way. This interface offers mechanisms for receiving notifications about device events and controlling device parameters, thereby playing a key role in the overall management and configuration of the system's kernel interfaces.

While other directories like /proc and /dev also serve specific purposes in the Linux filesystem hierarchy, they focus on different aspects. The /proc directory provides information about processes and system information but is more concerned with process-related data rather than the kernel and system hardware in the same structured manner as /sys. The /dev directory is intended for representing devices through special files, allowing for device file access but does not provide the same level of interaction with kernel subsystems.

By understanding the role of /sys in relation to the kernel and the overall system, one can appreciate why this is the correct answer in the context of interacting with system devices rather than processes.