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Chapter 2. The

proc

File System

Note

Any configuration changes you make using the echo command will disappear when the system is

restarted. To make your configuration changes take effect at the time the system is booted, see

Section 2.4.

The

/proc/sys/

directory contains several subdirectories controlling different aspects of a running

kernel.

2.3.9.1.

/proc/sys/dev/

This directory provides parameters for particular devices on the system. Most systems have at least

two directories,

cdrom

and

raid

, but customized kernels can have others, 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 3.12 2000/10/18

drive name:

hdc

drive speed:

32

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

This file can be quickly scanned to discover the qualities of an unknown CD ROM, at least in the eyes

of the kernel. 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 con 

trol the system's CD ROM. Use the

echo

command to enable or disable to disable these features.

If RAID support is compiled into the kernel, a

/proc/sys/dev/raid/

directory will be available

with at least two files in it:

speed_limit_min

and

speed_limit_max

. These settings determine

how much to accelerate the RAID device for particularly I/O intensive tasks, such as resyncing the

disks.

2.3.9.2.

/proc/sys/fs/

This directory contains an array of options and information concerning various aspects of the file

system, including quota, file handle, inode, and dentry information.

The

binfmt_misc

directory is used to provide kernel support for miscellaneous binary formats.

The important files in

/proc/sys/fs

include: