Expert Steps for building the packages

Prepare the pre built toolchain

For 64 bit systems:-

As better maintained toolchains are available for 64 bit architecture,Download and extract gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf.tar.xz from https://releases.linaro.org/components/toolchain/binaries/4.9-2017.01/arm-linux-gnueabihf/, follow the same steps to set the PATH as discussed in First Steps

Other versions of toolchain

Even though above versions are recommended initial work, you are free to choose a toolchain based on any gcc version, say v6.2.x available from https://releases.linaro.org/components/toolchain/binaries/ and keep getting updated time to time.Toolchain version used by Robert C Nelson’s script can be a better hint,which can be more compatible with for chosen kernel versions!!

Toolchain location

You can place the toolchain in /opt instead of ~/eworkdir, in such case /opt/gcc-linraro-4.9 to be add to PATH variable,you may ignore this step initially!!

export PATH=/opt/gcc-linaro-4.9/bin:$PATH

and update to .bashrc or .bash_profile as discussed earlier.

Building the kernel

Making story of KERNEL.tar.gz

git clone https://github.com/RobertCNelson/bb-kernel

cd bb-kernel

git checkout am335x-v4.9 #choose any Stable/LTS version like 4.1.x, 4.4.x

#copy system.sh.sample as system.sh and update CC to prevent downloading toolchain again

./build_kernel.sh

This steps require around 1 GB of download limit and takes some time to download entire repo from git.kernel.org,update necessary patches for the target board and build the kernel.

collect zImage, dtb file from deploy dir and especially config file (config-4.x.x-bonex.x) for further use.

cd KERNEL

make clean

tar -zcvf KERNEL.tar.gz KERNEL

Now this KERNEL.tar.gz, configuration file collected in deploy directory can be used independently without this build system.

Customzing configuration file

The configuration file collected above need some more changes, which can be applied as

During make ARCH=arm mencuconfig

Change General Setup ==> Local Version

Change General Setup ==> Kernel Compression Mode or install lzop tools using distro package manager

Device Drivers ==> Block Devices ==> RAM block device Support make it as static for initrd support

Device Drivers ==> Block Devices ==> Default RAM disk size(kbytes) increase to 65536 (64MB) from 16384(16MB) for RAM Disk with better space for dynamic modules, cross compiled apps Device Drivers ==> USB Support ==> USB Gadget Support ==> USB Gadget Drivers ==> Ethernet Gadget to select the target board as Ethernet gadget to use ethernet over usb functionality, this can enable networking between Host and Target via USB cable, some more scripts in internal Debian rootfs enable remote login over USB using this feature.

May enable OMAP Serial optionally, skip initially

Preparing rootfs

Making story of myootfs.img

Prepare your own image based the downloaded tarball core-image-minimal-beaglebone.tar.bz2 from https://downloads.yoctoproject.org/releases/yocto/yocto-2.2/machines/beaglebone/ as follows, you may replace v2.2 with desired version

dd if=/dev/zero of=myrootfs.img bs=1M count=32

sudo mkfs.ext4 myrootfs.img

sudo mkdir /mnt/image #one time

sudo mount -o loop,rw,sync myrootfs.img /mnt/image

sudo tar -jxvf core-image-minimal-beaglebone.tar.bz2 -C /mnt/image

sudo echo "SUBSYSTEM=="tty", ATTR{uartclk}!="0", KERNEL=="ttyS[0-9]", \

`SYMLINK+="ttyO%n" > /mnt/image/etc/udev/rules.d/60-omap-tty.rules`

i.e. add echo “SUBSYSTEM==”tty”, ATTR{uartclk}!=”0”, KERNEL==”ttyS[0-9]”, SYMLINK+=”ttyO%n” to /etc/udev/rules.d/60-omap-tty.rules , this is due to naming of debug port across kernel versions,some intermediate versions refer the serial debug port as /dev/ttyO2 ,where as recent versions again referring it as /dev/ttyS2, a symlink fix can work for all versions.

sudo umount /mnt/image