The sysfs is a RAM based virtual file system and provides details on various kernel objects. It provides a means to export kernel data structures, attributes and their linkages between the kernel objects and the user space.

if “CONFIG_SYSFS” is enabled during build, “sysfs” is in-built into the linux image. The  file system can also be mounted by using the command below

“mount -t sysfs sysfs /sys“

The kernel documentation “https://www.kernel.org/doc/Documentation/filesystems/sysfs.txt” provides information in great detail about sysfs. For every kernel object that is created, a directory is created in sysfs.  The below image shows the different folders that are present in “/sys” folder. It can be seen that most of the different Linux subsystems are placed in hierarchies and each has its own folder.

sysfs APIs and sample sysfs implementation in the Linux Kernel