Detecting Hardware
Objectives:
At the end of this episode, I will be able to:
1. Identify whether hardware has been detected by Linux and correct if necessary.
Additional resources used during the episode can be obtained using the download link on the overview
episode.
dmesg
List connected hardware
lspci
lsusb
Both commands call /sys (the sysfs) which contains a wide variety of device information
ls /sys/bus/pci/devices or ls /sys/bus/pci/drivers/e1000
Hardware devices are mapped to files in /dev
Udev <--> HAL <--> Dbus
Udev is the system that maps hardware to files in /dev
Provides dynamic naming so files represent hardware that is actually present
HAL populates the files with XML data
Dbus enables communications between HAL and the software process (file managers,
media players, etc)
All hardware is represented in /dev
/dev/cdrom
/dev/cpu
/dev/mem
/dev/sda
/dev/sda1
/dev/snd
/dev/stdout
/dev/tty##
Device mappings can be overridden if necessary
/etc/udev/rules.d
For example, say you removed eth0 and you now want eth1 to be eth0
vi /etc/udev/rules.d/70-persistent-net.rules
Correct names as required
Reboot is generally required
List loaded modules
lsmod Calls /proc which contains a wide variety of system information cat
/proc/modules
Cold plug / Hot plug
Loading modules
modprobe -v <module_name>
Not normally needed as kmod should load them when hardware is detected modinfo
<module_name>
Disabling Hardware
Option #1: If you installed the driver, simply remove the package.
Option #2: If it is built in to the distro, add it to the modprobe blacklist:
Determine the module name (lsmod)
sudoedit /etc/modprobe.d/blacklist.conf
Option #3: Use one of the following to temporarily remove it from memory (will return after
reboot)
rmmod
rmmod bluetooth
-f to force
-w to wait until unused
modprobe -r bluetooth
