This document discusses hardware settings and configuration on Linux systems. It covers determining hardware settings using HAL, D-Bus and Udev. It explains how HAL uses sysfs to store hardware information, how udev rules map hardware to device files in /dev, and how modules can be loaded, removed and listed. Kernel configuration files in /proc are also described. The document provides contact information for questions.

1. Hardware Settings
Hardware configuration and
settings on Linux
By John Troon

2. Determine & Configure Settings
● Determine Settings
– HAL (Hardware Abstraction Layer)
– Dbus
– Udev
● Configure Settings
– Set device ID
– Kernel modules
– Adding/removing devices

3. ● HAL – Hardware Abstraction Layer
– /sys and the hald
● Dbus
– Creates a channel on how information is transmited
between the hardware and the software.
● udev
– Determine how hardware and mounts are
represented on the system depending on the udev
rules

4. sysfs and procfs
● Sysfs is mounted at /sys
– This where HAL keeps database of the information of the Hardware
connected on the system.
● Procfs is mounted at /proc
– This is where the kernel keeps all of it's running commands. It's not
a real directory but a pseudo file created in the RAM when the
system boots.
– Configs are loaded here to affect the Kernel and you MUST be root
to make any of these temporary changes.
● E.g. /proc/sys/fs/file-max
● /proc/sys/net/ipv4/ip_forward

5. The udev
● The udev uses the udev rules to determine how
to represent hardware on a Linux system.
● These hardwares are mapped on /dev
– For instance the first harddrive on the system is
represented as /dev/sda if it has partitons, they will
be represented as /dev/sda1 /dev/sda2 and so on.
If we have a second harddrive, sdb and so on.
– lsusb, lspci, lshal, lspcmia, lshw

6. Kernel Modules
● To view loaded modules on the System, lsmod
● To remove a loaded module from the system,
rmmod
● To load a module to the running system,
modprobe (probes for all dependencies).

7. Device ID
● Instead of refering to devices on how they are
represented by the udev, you can refrence them by
their UUID as well.
● UUID – Unique Universal Identifire.
● Cat /proc/mounts
● Hotplug – add hardware while the computer is still on
● Coldplug – add hardware when the computer is
switched off.

8. Questions?
John Troon
Email: troon@linuxmail.org
Twitter: @johntroony