The document discusses the Linux kernel's regular updates, introducing new features, improving performance, and fixing issues. It provides guidance on compiling the kernel from source and using kernel modules, which are loaded as needed for device support. Additionally, it explains how the `udev` daemon manages device nodes, facilitating interactions between applications and hardware.

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2. Introduction
• A new Kernel comes out every 2 - 3 months
Current – 4.3
Next Release – 4.4 LTS ( Jan – Feb 2016 )
• What do you think there is so much to work on Kernel ?

3. Introduction
Here are what goes on each new Kernel release
 ReworkThings
 Improve performance
 Fix a Problem
 Add Support for New Device
 Add New Feature

4. Example
Support for Logitech Wireless Keyboard and Mouse

5. Kernel Modules
• Kernel supports most of the Devices
• Devices Drivers are implemented as Kernel modules
• Kernel modules are not part of Core Kernel

6. Kernel Modules
• Kernel modules are loaded only when they are required
• Eg – Kernel module usbhid is loaded when USB Mouse is
Attached
• Kernel Modules have .ko extension

7. Compiling Kernel From Source
~sudo su
# cd /usr/src
# curl https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-
4.3.tar.xz
# tar –xvJf linux-4.3.tar.xz
# cd linux-4.3
# apt-get update
# apt-get install build-essentials openssh-server libssl
libncurses libncurses-devel
# make menuconfig

8. Compiling Kernel From Source
Here we have option to support Devices based on Vendor, products
Eg – we can completely Disable support for usb devices itself

9. Compiling Kernel From Source
# make
# make modules
# make modules_install
# make install
# reboot
# uname –r
4.3
Compile main Kernel
Compile Kernel Modules
Install Kernel Modules - /lib/modules/4.3/
Install New Kernel - /boot
|->vmlinuz-4.3
|->System.map-4.3
|->vmlinuz-4.3
|->initrd.img-4.3
|->config-4.3
New Grub Entries are
automatically created

10. Kernel
• Kernel sends uevent when new device is plugged
• We can load Kernel modules with modprobe
# modprobe hid-generic

11. Udev
• Udev is daemon
• Udev is Device Manager for Linux Kernel
• Udev Operates in User Space
• Udev listens to Kernel uevents via netlink socket
• Primarily Manages Device Nodes in /dev
Device nodes are special files that allow
application to interface device drivers

12. What happens when USB Mouse or device is Plugged ?
udevd
USB mouse
is hotpluged
New uevent
Load usbhid
module
Create
New device node
/dev/input/mouse1
Application
Application &
Hardware interact
via device file &
module
1 5
4
3
2

13. Some Commands for Module Management
# lsmod
# modinfo
# modprobe
# insmod
# rmmod
# depmod
# udevadm
# dmesg
List of modules loaded in kernel
Get module info
Load a new module
Insert module from file
Remove a module
Check Dependency of module
Udev daemon Control
Prints Message buffer of Kernel

14. Shreyas MM www.shreyasmm.com

15. Shreyas MM www.shreyasmm.com