Kernel Development Learning Pipeline

E0 - The Big Upgrade 🎢

Build, install, and boot the latest Linux kernel fresh off Linus Torvalds’ tree.

Outcomes:

• Set up a kernel development environment

• Get comfortable with building the kernel

What to submit:

• Make a copy of E0.txt in your named directory

• Edit it as nescessary (don't forget to include the output of uname -a and dmesg | head and whoami on the system running your newly compiled Linux kernel.) and make a commit out of it

• Generate your patches

• Don't forget a cover letter

• All email code patches are expected to pass checkpatch.pl as described in the policies and procedures

• Submit your patches to exercise0@COURSE_DOMAIN

Procedure:

1. Install dependencies:

   • On Fedora, you can use:

     sudo dnf builddep kernel

   • This is roughly equivalent to:

   sudo dnf -y install gcc flex make bison openssl openssl-devel elfutils-libelf-devel ncurses-devel bc git tar dwarves

2. Install ccache to speed up subsequent kernel builds:

   sudo dnf -y install ccache

   • Be sure to restart your terminal after installing ccache so that it gets added to your path

3. Clone the latest (v6.5) Linux kernel release from: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git.

   git clone --depth=1 --branch v6.5 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
   

4. Change the current directory to the kernel tree

   cd linux
   

5. Copy the kernel config for your running kernel to your kernel source tree

   cp /boot/config-$(uname -r) .config
   

6. Set any new config options to the defaults

   make olddefconfig
   

7. Set a custom version tag for your kernel build. Edit "Makefile" and add something cool to the "EXTRAVERSION" variable. We suggest it begin with a '.' character. It must NOT contain spaces.

8. You can print the new version string to test it by:

   make kernelversion
   

9. Now, build the kernel. The -j option will invoke a parallel build using the number of threads specified. The $(nproc) will resolve to the output of the nproc command, and the nproc command will return the number of processor cores on your VM.

   make -j $(nproc)
   

10. Next, install the kernel modules for your newly build kernel onto your system. The directories you will be writing to are owned by root, so you need superuser permission (granted by wrapping your command with sudo) in order to complete this step.

    sudo make -j $(nproc) modules_install
    

11. Finally, install the new kernel into your system's /boot directory. The same superuser considerations from the previous step apply.

    sudo make install
    

12. Shutdown your VM

    sudo shutdown now
    

13. If you were running your VM in headless mode, boot your VM in normal mode (so you can see the console output, including the pre-OS bootloader).

    • When you power on your system, you should see a menu that looks roughly like the following:
    • As soon as it appears, hit the down arrow key to stop the countdown that will automatically boot the first selected menu entry in a couple of seconds.

    

14. Use the arrow keys to select your newly build kernel with your custom tag and hit enter when it is highlighted.

15. If you would like to set your new kernel as the default (i.e. it will boot automatically without selecting it at the menu), then use the following command to locate the index associated with your new kernel

    sudo grubby --info ALL
    

16. Then, use this number to set the default to that index

    sudo grubby --set-default-index <index>
    

17. Finally, when you have booted into your new kernel and logged in, run the following commands and save their output for the assignment submission.

    uname -a
    
    dmesg | head
    
    whoami
    

Seems easy enough right? 😉

Expect the compilation to take a little while Make sure you have 5-10 GB of free space on the partition where you are storing the kernel tree and a bit of extra space on whatever partition /boot resides in to store the new kernel image and initramfs.

Policies & Procedures