Building custom kernel

Use VM when you practice, just in case.

1. Download kernel

Download from https://www.kernel.org/pub/linux/kernel/.
For example,

sudo apt-get install -y wget xz-utils
wget https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.9.28.tar.xz
tar xf linux-4.9.28.tar.xz

2. Make your modification

Patch the files, add code, … etc.

3. Config

Copy current setting.

sudo cat /boot/config-`uname -r` > .config
make olddefconfig

4. Build

make -j4
make -j4 modules

5. Install

sudo make modules_install
sudo make install

Files will be written to /boot directory.

6. Reboot

Reboot the computer. If anything goes wrong, reboot again and select original kernel.

(Optional) Change default boot kernel

See here