Recommended setup :

• OS : Ubuntu LTS (22.04) or Debian stable
• CPU : Minimum of 6 cores and 12 threads
• RAM :
  • If DDR4 - 16 GB
  • if DDR5 - 12 GB
• Minimum of 50 GB free space
• Constant power and internet source (>5 MB/s)

Building steps

• Update and Upgrade the system

sudo apt update 
sudo apt upgrade -y

• install the necessary packages and dependencies

sudo apt install gawk wget git-core diffstat unzip texinfo gcc \
     build-essential chrpath socat cpio python3 python3-pip python3-pexpect \
     xz-utils debianutils iputils-ping python3-git python3-jinja2 libegl1-mesa \
     libsdl1.2-dev pylint xterm

• Clone the yocto repo and setup the environment

git clone https://git.yoctoproject.org/git/poky
cd poky
git checkout nanbield
source oe-init-build-env build-rpi32

• clone the other essential repo in home folder

• raspberrypi repo

git clone https://git.yoctoproject.org/meta-raspberrypi
cd meta-raspberrypi
git checkout nanbield 

• openembedded repo

git clone https://git.openembedded.org/meta-openembedded
cd meta-openembedded
git checkout nanbield 

• navigate to build-rpi folder in poky

cd /home/<user>/poky/build-rpi32

• open the bblayers.conf and edit it accordingly

• open the local.conf and edit it accordingly

• save the file and exit and setup locale

export LC_ALL=C.UTF-8
export LANG=C.UTF-8

• navigate to poky folder

cd /home/<user>/poky

• start building

bitbake core-image-base

• make sure you have a stable power and internet connection the build duration depends upon your cpu

• after the build i complete navigate to

/home/<user>/poky/build-rpi32/tmp/deploy/images

• if there is no tmp folder check for tmp-glibc to find your image

• insert the sd card and unmount partitions

• flash the image

sudo dd if=core-image-base-raspberrypi3.rootfs-<timestamp>.rootfs.rpi-sdimg of=/dev/sda bs=4M status=progress conv=fsync

• use the sync command again for safety
• boot the image

Note : you can also use the shell file to setup and build the yocto image

• use setup-environment.sh for setting up the environment
• use build-image.sh to build the image after manually editing the config files