block

Contains subdirectories for block devices. For example: /sys/block/sda.

bus

Contains subdirectories for each physical bus type, such as pci, pcmcia, scsi, or usb. Under each bus type, the devices directory lists discovered devices, and the drivers directory contains directories for each device driver.

class

Contains subdirectories for every class of device that's registered with the kernel.

dev

Contains the char/ and block/ directories. Inside these two directories are symbolic links named major:minor. These symbolic links point to the sysfs directory for the particular device. The /sys/dev directory provides a quick way to look up the sysfs interface for a device from the result of the stat(2) operation.

devices

Contains the global device hierarchy of all devices on the system. The platform directory contains peripheral devices such as device controllers that are specific to a particular platform. The system directory contains non peripheral devices such as CPUs and APICs. The virtual directory contains virtual and pseudo devices. See Oracle Linux 8: Managing System Devices With udev for more information about device management.

firmware

Contains subdirectories for firmware objects.

fs

Contains subdirectories for file system objects.

kernel

Contains subdirectories for other kernel objects

module

Contains subdirectories for each module loaded into the kernel. You can alter some parameter values for loaded modules. See Modprobe Configuration Reference.

Contains attributes that control the system's power state.