Chap8 Devices and UDEV Flashcards Preview

LFS201 > Chap8 Devices and UDEV > Flashcards

Flashcards in Chap8 Devices and UDEV Deck (15):
1

udev

device manager for discovering hardware and peripheral devices both during system boot, and later when they are connected to the system.
- It is the successor of devfs and hotplug.

2

device nodes

created automatically and then used by apps and o/s subsystems to communicate with and transfer data to and from devices

3

Character ('c') Device

Driver communicates by sending and receiving single characters (bytes, octes) IE. serial ports, sound cards

4

Block ('b') Device

Driver communicates by sending entire blocks of data IE. hard disks, USB cameras

5

Character and Block devices have filesystem entries associated with them; which devices do not?

Network devices.
These devices work by transmitting and receiving packets, which must be constructed by breaking up streams of data and reassembled

6

device driver

may manage multiple device nodes, which are normally placed in the /dev directory.

7

Major and Minor

numbers identify the driver associated with the device. 179 = major 0,1,2=minor
ryan@s6261-pi3:/lib/modules$ ls -l /dev/mmcblk0*
brw-rw---- 1 root disk 179, 0 Feb 11 2016 /dev/mmcblk0
brw-rw---- 1 root disk 179, 1 Feb 11 2016 /dev/mmcblk0p1
brw-rw---- 1 root disk 179, 2 Feb 11 2016 /dev/mmcblk0p2
The minor number is used only by the device driver to differentiate between the different devices it my control. IE. 1 and 2 HDD partition

8

The u in udev stands for?

user, and indicates that most of the work of creating, removing, and modifying device nodes is done in user-space

9

Persistent Device Naming?

names need not depend on the order of device connection or plugging in. Controlled by udev rules

10

library which allows access to information about the devices?

libudev

11

2 daemons that manages the /dev directory?

udevd
systemd-udevd

12

utility for control and diagnostics?

udevadm

13

/etc/udev/udev.conf

the main config file contains information such as where to place device nodes, default permissions and ownership. (Mostly empty file on new systems)

14

/etc/udev/rules.d

rules directory for device naming. IE. 30-usb.rules

15

udevadm info command to check HDD

$ sudo udevadm info /dev/sda