This is a short discurse about self kernel compilation on a arch system. Gentoo users are familiar with this kind of instructions or use the genkernel programm. You can find an article on archlinux

Install kernel sources and headers

pacman -S base-devel # only gcc and make
mkdir /usr/src/linux
cd /usr/src/linux

download the newest kernel release, at this moment it is 4.13.0

wget https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.13.2.tar.xz
wget https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.13.2.tar.sign
wget https://www.kernel.org/pub/linux/kernel/v4.x/sha256sums.asc

check the sha256 checksum and decompress the archive and check the sign. you can see the offical key from Greg Kroah-Hartman on the linux website.

grep 'linux-4.13.2.tar.xz' sha256sums.asc
064adc177a384a7aee6b18ef5d47c1cea3a43fae1aaa6aa95fdc97eb137ffcd1\
linux-4.13.2.tar.xz

sha256sum linux-4.13.2.tar.xz
064adc177a384a7aee6b18ef5d47c1cea3a43fae1aaa6aa95fdc97eb137ffcd1\
linux-4.13.2.tar.xz

unxz linux-4.13.2.tar.xz
gpg2 --verify linux-4.13.2.tar.sign
gpg2 --keyserver hkp://keys.gnupg.net --recv-keys \
647F28654894E3BD457199BE38DBBDC86092693E

when everything looks good continue with this steps

tar -xpf linux-4.13.2.tar
ln -s linux-4.13.2 linux;cd linux

Kernel configuration and compiling

Now we are in the kernel source tree. clean up the tree is a good thing to begin :-) if you have a kernel .config copy it to a save place.

make clean && make mrproper

Now the work begin to configure your specific kernel config. this will be saved in .config file in your kernel base dir. A good begin is to use your previously hand made config or use the current running:

make localmodconfig
# or the running arch config
zcat /proc/config.gz > .config

you will be asked about the new features. if you unsure use the default. after this a .config will be created in your kernel base dir. Now its time for you! use the old way with

cp .config ../config-default
make menuconfig

or the new interface

 make nconfig

After edit your configuration (super-slim config of my computer will to be download at the end of this article) buid your kernel. But before we install the modules we change the version of our Kernel in the Makefile. We will increase this number if we build a new kernel. So we have no conflicts with the modules… (-j NUMBER, is for the number of cores in your computer)

#nano -w Makefile
EXTRAVERSION = -acr-1

make -j3; make modules_install

Setting up your boot environment

When your compile process was successful you will be copy your kernel to your /boot folder (64-bit system). While I have a full encrypted system I need a ramdisk to open my partitions before I boot the initial system. So lets copy and make a ramdisk with the correct modules.

cp arch/x86_64/boot/bzImage /boot/kernel-4.13.2-acr-1
mkinitcpio -k 4.13.2-acr-1-ARCH -g /boot/initramfs-linux-4.13.img

And change your boot menu. I used the syslinux boot-manager. So my menu config looks like this.

#nano -w /boot/syslinux/syslinux.cfg#

LABEL arch-4.13.2-atr-1
    LINUX ../kernel-4.13.2-atr-1
    APPEND root=/dev/mapper/crypt cryptdevice=/dev/sda3:crypt\
    rootflags=subvol=__active/root rw intel_iommu=on amd_iommu=on
    INITRD ../initramfs-linux-4.13.img

syslinux-install_update -iam

And now reboot. If all is correct you will be get the password prompt of the crypt device and you systems boot correctly. But when you look of the size of your kernel…

Optimize your kernel settings

du -sh kernel-4.13.2-acr-1-ARCH initramfs-linux-4.13.img

5.2M    kernel-4.13.2-acr-1-ARCH
4.8M    initramfs-linux-4.13.img

This is not the optimization you want to. Its time to optimize your kernel needs.

cd /usr/src/linux/linux
make mrproper
cp ../config-default ./.config

#nano -w Makefile
EXTRAVERSION = -acr-2

make nconfig

Now you deselect all the options you doesn’t need for you computer and your setup. Sometimes its a difficult thing but when you look in the description of a kernel feature you will get an recommendation what you should do:

If you don’t know what this means you don’t need it. or

This is generally a good idea, so say Y.

Get you a smaller kernel size like 1MB? Its you challange…