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Linux From Scratch - Version 6.0

Chapter 6. Installing Basic System Software

6.57. Udev-030

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

Approximate build time: 0.2 SBU

Required disk space: 5.2 MB

Udev installation depends on: Coreutils and Make

6.57.1. Installation of Udev

Compile the package: 

make udevdir=/dev
udevdir=/dev

This tells udev in which directory devices nodes are to be created.

This package does not come with a test suite.

Install the package: 

make udevdir=/dev install

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

cp ../udev-config-2.permissions \
    /etc/udev/permissions.d/25-lfs.permissions
cp ../udev-config-1.rules /etc/udev/rules.d/25-lfs.rules

6.57.2. Contents of Udev

Installed programs: udev, udevd, udevsend, udevstart, udevinfo, and udevtest

Installed directory: /etc/udev

Short Descriptions

udev

Creates device nodes in /dev or renames network interfaces (not in LFS) in response to hotplug events

udevd

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

udevsend

Delivers hotplug events to udevd

udevstart

Creates device nodes in /dev that correspond to drivers compiled directly into the kernel; it performs that task by simulating hotplug events presumably dropped by the kernel before invocation of this program (e.g., because the root filesystem has not been mounted) and submitting such synthetic hotplug events to udev

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

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

/etc/udev

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