# Compiling Linux Kernel 4.9.124

<abstract>
	This article illustrates how to generate a bootable Linux Kernel
	image for RoadRunner D2, Acqua A5, Aria G25, Arietta G25 and FOX G20 boards
</abstract>

<div class="row"> 
	<div class="col-md-10" markdown="1">
	
### Notes, info, changelog, sources and links related to this version

* This procedure has been tested on Linux Ubuntu version 18.04
* The latest Linux Kernel version we tried writing this article is 4.9.124
* It is advisable to have a [Debug Port Interface](/DPI) or [similar](/USB-3V-SER) during the kernel bootstrap
* Before following this step by step procedure install [these packages](/arm9_toolchain)

	</div>

	<div class="col-md-2">
		<img src="tuxcase_small.jpg"/>
	</div>
</div>


##Step-by-step Kernel cross-compilation procedure:

Open a terminal on your Linux PC and download the Linux Kernel sources:

	wget https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.9.124.tar.xz

Extract the Kernel sources from the compressed file by typing:

	tar xvfJ linux-4.9.124.tar.xz

Move inside the just created new folder:

	cd linux-4.9.124

At this point I suggest to create a your own personal branch
of Linux Kernel sources with [git](https://git-scm.com/) to keep a trace of any changes from the
Kernel mainline using these commands.

	git init; git add .; git commit -m "Linux vanilla"; git branch acme; git checkout acme

Download the Acme Systems patch for this Kernel version. It add just the Acme boards defconfig, device trees and
small fewbug fixes:

	wget https://raw.githubusercontent.com/AcmeSystems/acmepatches/master/linux-4.9.patch

and apply it by typing:

	patch -p1 < linux-4.9.patch

Then select from the following list the right Linux configuration for your board by typing one of these commands:

	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- acme-roadrunner_defconfig
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- acme-acqua_defconfig
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-arietta_defconfig
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-xterm-01_defconfig
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-aria_defconfig
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-foxg20_defconfig

###Customize the default Linux Kernel configuration:

If you need to customize the Kernel configuration or you just want to take a look
around the Kernel setup type:

	make ARCH=arm menuconfig

and navigate inside the Kernel configuration using the arrow keys and 
following the help provided by the menuconfig interface.

### Create a defconfig of your own Kernel configuration

	make ARCH=arm savedefconfig


The file <code>defconfig</code> contains your configuration. You could rename and copy it in <code>arch/arm/configs/</code>

	cp defconfig arch/arm/configs/myboard_defconfig

###Generate the Device Tree Blob file (.dtb)

Now compile the device tree file requested by your board by selecting the right command from the following list:

	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- acme-roadrunner-bertad2.dtb
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- acme-acqua.dtb
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-arietta.dtb
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-xterm-01.dtb
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-aria.dtb
	make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- acme-foxg20.dtb

###Compile the Kernel image

Compile the Linux Kernel sources and generate the binary compressed 
image file to save in the first partition of microSD card.

####Roadrunner, Acqua

	make -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- zImage
	...
	Image arch/arm/boot/zImage is ready

####Aria, Arietta, Fox Board G25

	make -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- zImage
	...
	Image arch/arm/boot/zImage is ready

###Compile the Kernel modules

The image generated contains the Linux Kernel and all the built-in 
device drivers (option <b>[*]</b> in menuconfig) compiled with it.

Al the drivers compiled as external modules (option <b>[M]</b> in menuconfig)
need to be compiled and saved in the rootfs <code>/lib</code> directory on the second 
partition of the microSD. We didn't use any [M] flag in our defconfig so this procedure 
is not requested but. in case you add something. these are the commands to use
to compile them:

####Roadrunner, Acqua

	make modules -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf-
	make modules_install INSTALL_MOD_PATH=./modules ARCH=arm

####Aria, Arietta, Fox Board G25

	make modules -j8 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-
	make modules_install INSTALL_MOD_PATH=./modules ARCH=arm

##Copy the boot files into the first microSD partition

Insert a microSD [formatted microSD](/microsd_format) with the boot loader 
and the rootfs contents already created in your Linux PC and copy on it the files directly:

Write the Linux Kernel image, the Device tree blog files in the first microSD
partition and uncompress the modules in <code>/modules/lib</code> directory inside the second
microSD partition:

#### RoadRunner on Berta D2 board

	cp arch/arm/boot/dts/acme-roadrunner-bertad2.dtb /media/$USER/BOOT/acme-roadrunner.dtb
	cp arch/arm/boot/zImage /media/$USER/BOOT
	sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

####Acqua A5

	cp arch/arm/boot/dts/acme-acqua.dtb /media/$USER/BOOT/at91-sama5d3_acqua.dtb
	cp arch/arm/boot/zImage /media/$USER/BOOT
	sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

####Arietta G25

	cp arch/arm/boot/dts/acme-arietta.dtb /media/$USER/BOOT/acme-arietta.dtb
	cp arch/arm/boot/zImage /media/$USER/BOOT
	sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

####Arietta G25 on XTERM-01 board

	cp arch/arm/boot/dts/acme-xterm-01.dtb /media/$USER/BOOT/acme-arietta.dtb
	cp arch/arm/boot/zImage /media/$USER/BOOT
	sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

####Aria G25

	cp arch/arm/boot/dts/acme-aria.dtb /media/$USER/BOOT/at91-ariag25.dtb
	cp arch/arm/boot/zImage /media/$USER/BOOT
	sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.

####FOX Board G20

	cat arch/arm/boot/zImage arch/arm/boot/dts/acme-foxg20.dtb > /media/$USER/BOOT/uImage
	sudo rsync -avc modules/lib/. /media/$USER/rootfs/lib/.


## Remote writing via ssh 

Use this method if you have a working board accessible via LAN, WiFi or USB

Write the Linux Kernel image, the Device tree blog files in the first microSD
partition and uncompress the modules in <code>/modules/lib</code> directory inside the second
microSD partition:

#### RoadRunner on Berta D2 board

	scp arch/arm/boot/dts/acme-roadrunner-bertad2.dtb root@[ip_address]:/boot/acme-roadrunner.dtb	
	scp arch/arm/boot/zImage root@[ip_address]:/boot
	rsync -avc modules/lib/. root@[ip_address]:/lib/.

####Acqua A5

	scp arch/arm/boot/dts/acme-acqua.dtb root@[ip_address]:/boot/at91-sama5d3_acqua.dtb
	scp arch/arm/boot/zImage root@[ip_address]:/boot
	rsync -avc modules/lib/. root@[ip_address]:/lib/.

####Arietta G25

	scp arch/arm/boot/dts/acme-arietta.dtb root@192.168.10.10:/boot/acme-arietta.dtb
	scp arch/arm/boot/zImage root@192.168.10.10:/boot
	rsync -avc modules/lib/. root@192.168.10.10:/lib/.

####Arietta G25 with XTERM-01

	scp arch/arm/boot/dts/acme-xterm-01.dtb root@192.168.10.10:/boot/acme-arietta.dtb
	scp arch/arm/boot/zImage root@192.168.10.10:/boot
	rsync -avc modules/lib/. root@192.168.10.10:/lib/.

####Aria G25

	scp arch/arm/boot/dts/acme-aria.dtb root@[ip_address]:/boot/at91-ariag25.dtb
	scp arch/arm/boot/zImage root@[ip_address]:/boot
	rsync -avc modules/lib/. root@[ip_address]:/lib/.

####FOX Board G20

	cat arch/arm/boot/zImage arch/arm/boot/dts/acme-foxg20.dtb > uImage
	scp uImage root@[ip_address]:/boot
	rsync -avc modules/lib/. root@[ip_address]:/lib/.

<span class="smallnotes">
If this command doesn't work verify if rsync in installed on your board. Use <code>apt-get install rsync</code>.
</span>

##After the first boot

At the first access to the board command line update the module dependencies by typing this command:

	depmod -a

## Links

* [The Linux Kernel Archives](https://www.kernel.org)
* [Linux versions changelog](https://kernelnewbies.org/LinuxVersions)

@include='bio_tanzilli'