Building a Custom Linux Kernel

Getting the source

The latest (stable) source can be downloaded from the official kernel page.

Creating the config

The used configuration can either be adapted from another distribution or generated from scratch by running

$ make menuconfig

The controls are as follows

/: Search for an item
y: Enable item
n: Disable item

I’d suggest to alter the following parameters

CONFIG_LOCALVERSION: Give your kernel some name

Compilation & Installation

As you probably already suspected, the kernel can be compiled by simply running

$ make

In order to be able to boot into your kernel, it has to be installed to /boot

$ cp arch/x86/boot/bzImage /boot/vmlinuz-custom

You might want to replace custom with something you can remember more easily.

Finally, don’t forget to install your modules

$ make modules_install

Creating the initial ramdisk (initrd)

The initial ramdisk can be easily created by calling

$ mkinitcpio -k <kernel> -g <image>

In our case, <kernel> would be ‘/boot/vmlinuz-custom’ and <image> would be ‘/boot/initrd-custom.img’.

Adding the boot entry

In order to actually find your custom kernel on boot, you have to tell grub about it. Do so by adding a new entry to /etc/grub.d/40_custom (or a similarly named file in that directory).

You can also skip this step and let grub generate a default entry by simply calling grub-mkconfig as shown below.

In the former case, the entry should look something like

menuentry 'Linux, the custom one' {
    set root=<partition>
    linux <kernel>
    initrd <image>
}

(with <kernel>=’/boot/vmlinuz-custom’ and <image>=’/boot/initrd-custom.img’)

Setting <partition> correctly can be a bit tricky. It’s of the form ‘(hdX,Y)’, where ‘X’ encodes the hard drive (0=sda, 1=sdb, …) and ‘Y’ the partition. Consequently, ‘(hd0,gpt4)’ would code for sda4.

These changes can then be committed to /boot/grub/grub.cfg by running

$ grub-mkconfig -o /boot/grub/grub.cfg