Linux From Scratch - Version Udev_update-20060210

Chapter 6. Installing Basic System Software

6.59. Udev-084

The Udev package contains programs for dynamic creation of device nodes.

Approximate build time: 0.1 SBU
Required disk space: 3.1 MB
Installation depends on: Coreutils and Make

6.59.1. Installation of Udev

Create some devices that Udev cannot handle due to them being required very early in the boot process: 

ln -sv /proc/self/fd /lib/udev/devices/fd
ln -sv /proc/self/fd/0 /lib/udev/devices/stdin
ln -sv /proc/self/fd/1 /lib/udev/devices/stdout
ln -sv /proc/self/fd/2 /lib/udev/devices/stderr
ln -sv /proc/kcore /lib/udev/devices/core

Compile the package: 

make \
EXTRAS="extras/ata_id extras/cdrom_id extras/edd_id extras/firmware extras/floppy extras/scsi_id extras/usb_id extras/volume_id"

The meaning of the make option:

EXTRAS=...

This builds several helper binaries that can aid in writing custom Udev rules.

To test the results, issue: make test.

Install the package: 

make DESTDIR=/ \
EXTRAS="extras/ata_id extras/cdrom_id extras/edd_id extras/firmware extras/floppy extras/scsi_id extras/usb_id extras/volume_id" \
install

The meaning of the make parameter:

DESTDIR=/

This prevents the Udev build process from killing any udevd processes that may be running on the host system.

Udev's configuration is far from ideal by default, so install the configuration files here: 

cp -v ../udev-config-5.rules /etc/udev/rules.d/25-lfs.rules

Alter Udev's configuration file so that Udev can automatically load kernel modules. 

sed -i 147,150d /etc/udev/rules.d/25-lfs.rules
cat >> /etc/udev/rules.d/25-lfs.rules << EOF
# Rules to allow hotplugging of devices with modular drivers
ACTION=="add", SUBSYSTEM=="usb", MODALIAS=="*", \
  RUN+="/sbin/modprobe $modalias"
ACTION=="add", SUBSYSTEM=="scsi", SYSFS{type}=="[07]", \
  RUN+="/sbin/modprobe sd_mod"
EOF

Install the documentation that explains how to create Udev rules: 

install -m644 -D -v docs/writing_udev_rules/index.html /usr/share/doc/udev-084/index.html

Run the udevstart program to create our full complement of device nodes. 

/sbin/udevstart

6.59.2. Contents of Udev

Installed programs: ata_id, cdrom_id, create_floppy_devices, edd_id, firmware_helper, scsi_id, udevcontrol, udevd, udevinfo, udevmonitor, udevtest, usb_id and vol_id
Installed directory: /etc/udev

Short Descriptions

ata_id

Provides udev with a unique string and additional information (uuid, label) for an ATA drive

cdrom_id

Provides udev with the capabilities of a CD-ROM or DVD-ROM drive

create_floppy_devices

Creates all possible floppy devices based on the CMOS type

edd_id

Provides udev with the EDD ID for a BIOS disk drive

firmware_helper

Enables udev to upload firmware to devices

scsi_id

Provides udev with a unique SCSI identifier based on the data returned from sending a SCSI INQUIRY command to the specified device

udevcontrol

Configures a number of options for the running udevd daemon, such as the log level.

udevd

A daemon that reorders hotplug events before submitting them to udev, thus avoiding various race conditions

udevinfo

Allows users to query the udev database for information on any device currently present on the system; it also provides a way to query any device in the sysfs tree to help create udev rules

udevmonitor

Prints the event received from the kernel and the event which udev sends out after rule processing

udevtest

Simulates a udev run for the given device, and prints out the name of the node the real udev would have created or (not in LFS) the name of the renamed network interface

usb_id

Provides udev with information about USB devices

vol_id

Provides udev with the label and uuid of a filesystem

/etc/udev

Contains udev configuation files, device permissions, and rules for device naming