Device Information: /proc and /etc/sysconfig/hwconf

On Red Hat, Kudzu maintains a complete profile of all your installed hardware devices in the /etc/sysconfig/hwconf file (/etc/sysconfig is discussed in Chapter 30). As noted previously, this file is updated by Kudzu (kudzu); your new hardware is added and old devices removed. Entries define configuration variables such as a device's class (video, CD-ROM, hard drive, and so on) the bus it uses (PCI, IDE, and so on), its device name (such as hdd or st0), the drivers it uses, and a description of the device. A mouse entry is shown here:

class: MOUSE
bus: PSAUX
detached: 0
device: psaux
driver: generic3ps/2
desc: "Generic 3 Button Mouse (PS/2)"

The /proc file system (see Chapter 30) maintains special information files for your devices. The /proc/devices file lists all your installed character and block devices along with their major numbers. IRQs, DMAs, and I/O ports currently used for devices are listed in the interrupts, dma, and ioports files, respectively. Certain files list information covering several devices, such as pci, which lists all your PCI devices, and sound, which lists all your sound devices. The sound file lists detailed information about your sound card. Several subdirectories, such as net, ide, and scsi, contain information files for different devices. Certain files hold configuration information that can be changed dynamically, like the IP packet forwarding capability and the maximum number of files. You can change these values with the redhat-config-proc tool (Kernel Tuning in the System Tools menu) or by manually editing certain files. Table 32-2 lists several device-related /proc files (see Chapter 30 for other entries).

Table 32-2: Proc Device Information Files

File	Description
/proc/devices	Lists the device drivers configured for the currently running kernel
/proc/dma	Displays the DMA channels currently used
/proc/interrupts	Displays the IRQs (interrupts) in use
/proc/ioports	Shows the I/O ports in use
/proc/pci	Lists PCI devices
/proc/sound	Lists sound devices
/proc/scsi	Directory for SCSI devices
/proc/ide	Directory for IDE devices
/proc/net	Directory for network devices