00. Build

Host machine

Building a gentoo 64-bit system for Raspberry Pi 4. I'm using a laptop with Ubuntu 20.04 as a host machine. You need following packages installed:

sudo apt-get install build-essential gawk gcc g++ gfortran git texinfo bison libncurses-dev flex libssl-dev gcc-aarch64-linux-gnu g++-aarch64-linux-gnu

Get the sources

cd 
mkdir rpi-64
cd rpi-64
git clone --depth=1 https://github.com/raspberrypi/firmware -b stable 
git clone --depth=1 https://github.com/raspberrypi/linux -b rpi-5.15.y
wget http://distfiles.gentoo.org/releases/arm64/autobuilds/current-stage3-arm64-desktop-openrc/stage3-arm64-desktop-openrc-20220227T233703Z.tar.xz
wget https://mirror.leaseweb.com/gentoo/snapshots/portage-latest.tar.bz2

Preparing the SD card

as decribed here (gentoo wiki).

Installation

Mounting the partitions

sudo mkdir /mnt/gentoo
sudo mount /dev/mmcblk0p3 /mnt/gentoo
sudo mkdir /mnt/gentoo/boot/
sudo mount /dev/mmcblk0p1 /mnt/gentoo/boot

Extracting files


sudo tar xpfv stage3-arm64-desktop-openrc-20220227T233703Z.tar.xz --xattrs-include='*.*' --numeric-owner -C /mnt/gentoo/

sudo mkdir /mnt/gentoo/var/db/repos/gentoo
sudo tar xvpf portage-latest.tar.bz2 --strip-components=1 -C /mnt/gentoo/var/db/repos/gentoo

Cross compiling and installing kernel, modules and device tree

cd linux
ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make distclean
ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make bcm2711_defconfig
ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make -j4 Image modules dtbs
sudo ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make modules_install INSTALL_MOD_PATH=/mnt/gentoo
cd ..

sudo cp -vr firmware/boot/* /mnt/gentoo/boot/
sudo cp -vr firmware/modules /mnt/gentoo/lib
sudo cp -vr linux/arch/arm64/boot/dts/overlays/*.dtbo /mnt/gentoo/boot/overlays
sudo cp -v linux/arch/arm64/boot/dts/broadcom/bcm2711-rpi-4-b.dtb /mnt/gentoo/boot/
sudo cp -v linux/arch/arm64/boot/Image /mnt/gentoo/boot/kernel8.img

Configuration

get some config files:

wget https://github.com/mck-sbs/gentoo-rpi-64-bit/raw/main/fstab
wget https://github.com/mck-sbs/gentoo-rpi-64-bit/raw/main/inittab
wget https://github.com/mck-sbs/gentoo-rpi-64-bit/raw/main/config.txt
wget https://github.com/mck-sbs/gentoo-rpi-64-bit/raw/main/cmdline.txt

sudo mv /mnt/gentoo/etc/fstab /mnt/gentoo/etc/fstab_bak
sudo mv fstab /mnt/gentoo/etc/

sudo mv /mnt/gentoo/etc/inittab /mnt/gentoo/etc/inittab_bak
sudo mv inittab /mnt/gentoo/etc/

sudo mv /mnt/gentoo/boot/config.txt /mnt/gentoo/boot/config_txt_bak
sudo mv config.txt /mnt/gentoo/boot/

sudo mv cmdline.txt /mnt/gentoo/boot/

List the timezones:

ls /mnt/gentoo/usr/share/zoneinfo

and choose one:

sudo cp /mnt/gentoo/usr/share/zoneinfo/Europe/Berlin /mnt/gentoo/etc/localtime
sudo echo "Europe/Berlin" > /mnt/gentoo/etc/timezone

clrear root password:

sudo sed -i 's/^root:.*/root::::::::/' /mnt/gentoo/etc/shadow

set keymap:

sudo sed -i 's/^keymap="us"/keymap="de"/' /mnt/gentoo/etc/conf.d/keymaps

Unmount SD

sudo umount /mnt/gentoo/boot
sudo umount /mnt/gentoo

Back up

Before you put in your SD card and boot the rpi, you should back up your sd card:

sudo dd if=/dev/mmcblk0 of=image.img

ToDo shrink 

https://medium.com/platformer-blog/creating-a-custom-raspbian-os-image-for-production-3fcb43ff3630