4. sysfs

Sysfs was created long ago to better manage devices on our system that the /dev directory failed to do. Sysfs is a virtual filesystem, most often mounted to the /sys directory. It gives us more detailed information than what we would be able to see in the /dev directory. Both directories /sys and /dev seem to be very similar and they are in some regards, but they do have major differences. Basically, the /dev directory is simple, it allows other programs to access devices themselves, while the /sys filesystem is used to view information and manage the device.

The /sys filesystem basically contains all the information for all devices on your system, such as the manufacturer and model, where the device is plugged in, the state of the device, the hierarchy of devices and more. The files you see here aren't device nodes, so you don't really interact with devices from the /sys directory, rather you are managing devices.

Take a look at the contents of the /sys directory:

pete@icebox:~$ ls /sys/block/sda

alignment_offset  discard_alignment  holders   removable  sda6       trace

bdi               events             inflight  ro         size       uevent

capability        events_async       power     sda1       slaves

dev               events_poll_msecs  queue     sda2       stat

device            ext_range          range     sda5       subsystem