This directory provides parameters for particular devices on the system. Most systems have at least two directories, cdrom/ and raid/. Customized kernels can have other directories, such as parport/, which provides the ability to share one parallel port between multiple device drivers.

The cdrom/ directory contains a file called info, which reveals a number of important CD-ROM parameters:

CD-ROM information, Id: cdrom.c 3.20 2003/12/17   
drive name:             hdc 
drive speed:            48 
drive # of slots:       1 
Can close tray:         1 
Can open tray:          1 
Can lock tray:          1 
Can change speed:       1 
Can select disk:        0 
Can read multisession:  1 
Can read MCN:           1 
Reports media changed:  1 
Can play audio:         1 
Can write CD-R:         0 
Can write CD-RW:        0 
Can read DVD:           0 
Can write DVD-R:        0 
Can write DVD-RAM:      0 
Can read MRW:           0 
Can write MRW:          0 
Can write RAM:          0

This file can be quickly scanned to discover the qualities of an unknown CD-ROM. If multiple CD-ROMs are available on a system, each device is given its own column of information.

Various files in /proc/sys/dev/cdrom, such as autoclose and checkmedia, can be used to control the system's CD-ROM. Use the echo command to enable or disable these features.

If RAID support is compiled into the kernel, a /proc/sys/dev/raid/ directory becomes available with at least two files in it: speed_limit_min and speed_limit_max. These settings determine the acceleration of RAID devices for I/O intensive tasks, such as resyncing the disks.