Sysclass

Sysclass is a component of the Linux kernel's sysfs filesystem, exposing device classes under the /sys/class directory. It provides a stable, user-space view of kernel device objects, grouping devices by class and enabling basic querying and configuration.

Within /sys/class, each class has its own directory, such as net for network interfaces, block for block devices, input for input devices, and video4linux for video devices. Under a class directory are per-device subdirectories, each representing a specific device instance. These directories contain symbolic links to the device's object in /sys/devices and to the bound driver, as well as a set of attributes that describe the device's characteristics (for example, modalias, subsystem, and class-specific settings).

Sysclass information is primarily consumed by user-space utilities such as udev to enumerate devices and create device nodes, and by administrative scripts and tools that read or write attributes to tune behavior at runtime. It is part of the Linux device model introduced to provide a consistent interface for hardware discovery and management. Access to sysfs files may require appropriate permissions, and writing to attributes can alter kernel-managed behavior.

See also: sysfs, /sys, Linux device model, udev.