1. Operating System Kernel Compilation
Sarah Diesburg
CS 3430
Operating Systems

2. Kernel Coding The next project involves compiling a new kernel!
Fun but challenging….
Each person/team will get their own virtual machine(s)
See website instructions for how to install/use the virtual machine

3. Booting with the Bootloader (grub2)
The newest version of the kernel will boot by default
Look in the submenu (or further down the list) for any older version

4. Logging In Username: user Password: user Username: root
Password: iamr00t

5. Communicating with your fresh virtual machine
Use the GUI
Select the terminal program from the bottom of the left shortcuts bar

6. Communicating with your fresh virtual machine (other ways)
Use ssh
Log into the terminal, and issue /sbin/ifconfig to get the second IP address
Type the IP address directly into PuTTY
Transfer files
Must use Winscp or Filezilla with the IP address found above
Basically, communicate with it the same way you communicated with the student.cs.uni.edu machine

7. SSH/WinSCP Demo… Issue this command inside VM to get its IP address

8. If you created your own virtual machine….
Good for you!
You will want to install these packages:
gcc / flex / bison
make
ssh
vim / emacs / (your choice of editor)
libssl-dev
libncurses5-dev
others (heh heh)

9. Kernel Compilation

10. Example of Kernel Compilation….

11. Choosing a Kernel The next project will involve kernel development
We all need to be in the same boat…
The class version will be (bleeding edge stable version)

12. Kernel Repository
– place to download latest and greatest Linux kernels!
Traditional place for kernel is in /usr/src/
It is already in there for you
…That is, unless you created your own virtual machine. Then download it from kernel.org, and extract it with the command
$> tar xv linux tar.xz

13. Compiling the Kernel
Compiles based on configuration of .config file located in the kernel source directory
How can I correctly configure my kernel?
Use the ‘make oldconfig’ command
Use the ‘make menuconfig’ command

14. ‘make oldconfig’
This command makes the default configuration file for Linux.
It creates a new configuration file based on the old configuration, so the kernel has the right mix of drivers

15. ‘make menuconfig’
Only do this if you are trying to make the kernel smaller
Manually select and deselect drivers and options for your kernel
* -- compiled directly into kernel
M – compiled into a module (driver) that can be dynamically added
Can be tough to figure out what you need and don’t need
Command ‘lspci’ shows hardware on computer

16. ‘make menuconfig’

17. ‘lspci’

18. General Linux Source Organization
Memory Management
Networking Layer
Security
Sound Processing
Architecture-specific Code
Disk Drivers
Devices
File Systems

19. Config Example (Inside Source Dir)
$> cd /usr/src/linux $> make oldconfig $> make menuconfig

20. Compiling the Kernel Issue ‘make’ inside the source directory
Grab some coffee….

21. Installing the Kernel Install the modules (drivers)
$> make modules_install
Install the actual kernel
$> make install

22. Historical final steps
Now the ‘make install’ command does all the following for you
Create a ramfs image
Update grub

23. Boot Driver Problem Why ramfs?
Suppose you compiled the disk drivers and root file system drivers as modules
Boot process loads the kernel image
Kernel image does not contain disk drivers

24. Configure the Boot Loader (Grub)
Update bootloader (no longer necessary with ‘make install’)
$> sudo update-grub
Now you can issue a reboot and cross your fingers!
$> sudo reboot

25. Telling Which Kernel You are In
Select the new kernel from the grub menu!
Watch your virtual machine
If something goes wrong, reboot and go back into your original kernel to try again
The following command will tell you which kernel you are in:
$> uname -r

26. Uh oh…. If it doesn’t boot, go back into the original kernel
Always important to have one working kernel!
Make sure you didn’t skip a step…
You may have taken too much out of the kernel…
Start with bloated kernel, take things out one by one

27. Project 2 Spec
Let’s take a look at it