sysfs is a Linux pseudo filesystem that is used to export information, and runtime configuration support from drivers into userspace. By convention (LSB) it's mounted on /sys.

The sysfsutils package contains a library and command line tool (systool) to explore /sys and display and alter current settings. The Debian package at least uses this tool to provide boot time configuration of SysFs values through the /etc/sysfs.conf file.

Also note that some kernel options are still configured through /proc/sys or using sysctl and at boot time through /etc/sysctl.conf. A general rule of thumb is that if the kernel option is related directly to some piece of hardware, it's probably configured via sysfs, and if it's to do with other kernel behaviour, it'll be accessable via /proc/sys

EG: RAID, SCSI and other block device configuration such as IO Elevators are configured via SysFs. Network card settings such as MTU can be set via SysFs, but network protocol settings are tweaked through sysctl.

See SysctlNotes for more information.

CategorySystemAdministration, CategoryNotes