Compiling and Deploying BeagleBone Black Kernel

- Prerequisites

sudo apt update
sudo apt upgrade

Gparted :

sudo apt-get install gparted

Minicom :

sudo apt-get install minicom

MkImage :

sudo apt-get install uboot-tools

- Installing ARM cross compiler toolchain

Install:

sudo apt install git bc bison flex libssl-dev make libc6-dev libncurses5-dev
sudo apt install crossbuild-essential-armhf

To check if it is correctly installed and the version:

arm-linux-gnueabihf-gcc --version	

- U-boot

U-boot is an open source universal bootloader for Linux systems. It supports features like TFTP, DHCP, NFS etc… In order to boot the kernel, a valid kernel image (uImage) is required.

It is not possible to explain u-boot here, as it is beyond the scope of this post. So, we will see how to produce a bootable image using U-boot. You can either follow the below steps to compile your own U-boot image or you could just get a prebuilt image.

Download:

mkdir -p ~/Beaglebone
cd ~/Beaglebone
git clone -b v2022.04 https://github.com/u-boot/u-boot --depth=1

Compile :

cd u-boot
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- distclean
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- am335x_evm_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-

- Building a kernel for beaglebone black

Cloning the Kernel

cd ~/Beaglebone
git clone https://github.com/beagleboard/linux.git

Go to the linux directory and ensure that you have cloned the correct repo by executing the following command :

cd linux/
git remote -v 

• You should get this below output

  origin https://github.com/beagleboard/linux.git (fetch)
  origin https://github.com/beagleboard/linux.git (push)

Default Configuration ;

sudo make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- omap2plus_defconfig

Compile the kernel :

sudo make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- uImage dtbs LOADADDR=0x80008000 -j8

- Install Kernel Modules

sudo make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j8 modules

- Formatting the SD card

sudo gparted

• Insert your sd card by means of card reader and open Gparted. Select your sd card from the top right corner. it will be something like this, “/dev/sdb”

• Right click on the rectangular area showing your sd card name and select unmount as we need to unmount the existing partitions.

• Then, delete the existing partitions by again right clicking and selecting “delete”. This will delete all your files in sd card.

• We need two partitions in order to boot the kernel, one is for storing the bootable images and another one is for storing the minimal RFS(Root File System).

1. Click Add button. Then, create partition for storing BOOT by entering the options below

    New size: 1024 MB
    File System: FAT32
    Label: BOOT

2. Click Add button. Then, create another partition for storing rootfs by entering the options below

    New Size: (Remaining)
    File System: EXT4
    Label: rootfs

• Finally, click the green tick mark at the menu bar.

- Install Kernel Modules on SD Card

sudo make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- INSTALL_MOD_PATH=/media/$USER/rootfs/ modules_install

- Root File System (RFS)

Clone the Root file system :

cd ~/Beaglebone
git clone https://github.com/Saishivareddy/Rootfs/
cd Rootfs/

Copy the files into the partition in SD Card ;

sudo tar -xvf rootfs.tar.xz -C /media/$USER/rootfs/
cd /media/$USER/rootfs/rootfs/
sudo mv ./* ../
cd ../
sudo rmdir rootfs

- Copy Image and dtbs on SD Card(Boot)

cd ~\Beaglebone/linux/
cp arch/arm/boot/uImage /media/$USER/BOOT
cp arch/arm/boot/dts/am335x-boneblack.dtb /media/$USER/BOOT

vim /media/$USER/BOOT/uEnv.txt

• Copy the below code into that

console=ttyS0,115200n8
netargs=setenv bootargs console=ttyO0,115200n8 root=/dev/mmcblk0p2 ro rootfstype=ext4 rootwait debug earlyprintk mem=512M
netboot=echo Booting from microSD ...; setenv autoload no ; load mmc 0:1 ${loadaddr} uImage ; load mmc 0:1 ${fdtaddr} am335x-boneblack.dtb ; run netargs ; bootm ${loadaddr} - ${fdtaddr}
uenvcmd=run netboot

• After completing the above steps you can find the following files in BOOT partition of sd card.
  • uImage
  • am335x-boneblack.dtb
  • uEnv.txt